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[Xen-changelog] [xen-unstable] [LINUX] Eliminates a deadlock and reduce

To: xen-changelog@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-changelog] [xen-unstable] [LINUX] Eliminates a deadlock and reduce (sometimes significantly) the time
From: Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 14 Jun 2006 15:25:29 +0000
Delivery-date: Wed, 14 Jun 2006 08:28:07 -0700
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# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 2fea03842f404f96955763caf803a29481953750
# Parent  5d4b9dc8821809768c2948f625e6f7e5597f4b5c
[LINUX] Eliminates a deadlock and reduce (sometimes significantly) the time
interrupts are off during context switch.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
---
 linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c                    |    6 
 linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c                 |    6 
 linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/mmu.h           |    4 
 linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/mmu_context.h   |   11 
 linux-2.6-xen-sparse/include/asm-x86_64/mach-xen/asm/mmu.h         |    4 
 linux-2.6-xen-sparse/include/asm-x86_64/mach-xen/asm/mmu_context.h |   12 
 linux-2.6-xen-sparse/kernel/fork.c                                 | 1619 
++++++++++
 7 files changed, 1653 insertions(+), 9 deletions(-)

diff -r 5d4b9dc88218 -r 2fea03842f40 
linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c
--- a/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c   Tue Jun 13 15:41:27 
2006 +0100
+++ b/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c   Tue Jun 13 15:56:28 
2006 +0100
@@ -614,6 +614,12 @@ void mm_pin_all(void)
        }
 }
 
+void _arch_dup_mmap(struct mm_struct *mm)
+{
+       if (!test_bit(PG_pinned, &virt_to_page(mm->pgd)->flags))
+               mm_pin(mm);
+}
+
 void _arch_exit_mmap(struct mm_struct *mm)
 {
        struct task_struct *tsk = current;
diff -r 5d4b9dc88218 -r 2fea03842f40 
linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c
--- a/linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c        Tue Jun 13 
15:41:27 2006 +0100
+++ b/linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c        Tue Jun 13 
15:56:28 2006 +0100
@@ -130,6 +130,12 @@ void mm_pin_all(void)
                                  context.unpinned));
 }
 
+void _arch_dup_mmap(struct mm_struct *mm)
+{
+    if (!mm->context.pinned)
+        mm_pin(mm);
+}
+
 void _arch_exit_mmap(struct mm_struct *mm)
 {
     struct task_struct *tsk = current;
diff -r 5d4b9dc88218 -r 2fea03842f40 
linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/mmu.h
--- a/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/mmu.h  Tue Jun 13 
15:41:27 2006 +0100
+++ b/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/mmu.h  Tue Jun 13 
15:56:28 2006 +0100
@@ -18,4 +18,8 @@ extern void _arch_exit_mmap(struct mm_st
 extern void _arch_exit_mmap(struct mm_struct *mm);
 #define arch_exit_mmap(_mm) _arch_exit_mmap(_mm)
 
+/* kernel/fork.c:dup_mmap hook */
+extern void _arch_dup_mmap(struct mm_struct *mm);
+#define arch_dup_mmap(mm, oldmm) ((void)(oldmm), _arch_dup_mmap(mm))
+
 #endif
diff -r 5d4b9dc88218 -r 2fea03842f40 
linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/mmu_context.h
--- a/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/mmu_context.h  Tue Jun 
13 15:41:27 2006 +0100
+++ b/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/mmu_context.h  Tue Jun 
13 15:56:28 2006 +0100
@@ -51,8 +51,7 @@ static inline void switch_mm(struct mm_s
        struct mmuext_op _op[2], *op = _op;
 
        if (likely(prev != next)) {
-               if (!test_bit(PG_pinned, &virt_to_page(next->pgd)->flags))
-                       mm_pin(next);
+               BUG_ON(!test_bit(PG_pinned, &virt_to_page(next->pgd)->flags));
 
                /* stop flush ipis for the previous mm */
                cpu_clear(cpu, prev->cpu_vm_mask);
@@ -99,7 +98,11 @@ static inline void switch_mm(struct mm_s
 #define deactivate_mm(tsk, mm) \
        asm("movl %0,%%fs ; movl %0,%%gs": :"r" (0))
 
-#define activate_mm(prev, next) \
-       switch_mm((prev),(next),NULL)
+static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
+{
+       if (!test_bit(PG_pinned, &virt_to_page(next->pgd)->flags))
+               mm_pin(next);
+       switch_mm(prev, next, NULL);
+}
 
 #endif
diff -r 5d4b9dc88218 -r 2fea03842f40 
linux-2.6-xen-sparse/include/asm-x86_64/mach-xen/asm/mmu.h
--- a/linux-2.6-xen-sparse/include/asm-x86_64/mach-xen/asm/mmu.h        Tue Jun 
13 15:41:27 2006 +0100
+++ b/linux-2.6-xen-sparse/include/asm-x86_64/mach-xen/asm/mmu.h        Tue Jun 
13 15:56:28 2006 +0100
@@ -28,6 +28,10 @@ extern spinlock_t mm_unpinned_lock;
 /* mm/memory.c:exit_mmap hook */
 extern void _arch_exit_mmap(struct mm_struct *mm);
 #define arch_exit_mmap(_mm) _arch_exit_mmap(_mm)
+
+/* kernel/fork.c:dup_mmap hook */
+extern void _arch_dup_mmap(struct mm_struct *mm);
+#define arch_dup_mmap(mm, oldmm) ((void)(oldmm), _arch_dup_mmap(mm))
 #endif
 
 #endif
diff -r 5d4b9dc88218 -r 2fea03842f40 
linux-2.6-xen-sparse/include/asm-x86_64/mach-xen/asm/mmu_context.h
--- a/linux-2.6-xen-sparse/include/asm-x86_64/mach-xen/asm/mmu_context.h        
Tue Jun 13 15:41:27 2006 +0100
+++ b/linux-2.6-xen-sparse/include/asm-x86_64/mach-xen/asm/mmu_context.h        
Tue Jun 13 15:56:28 2006 +0100
@@ -73,8 +73,7 @@ static inline void switch_mm(struct mm_s
        struct mmuext_op _op[3], *op = _op;
 
        if (likely(prev != next)) {
-               if (!next->context.pinned)
-                       mm_pin(next);
+               BUG_ON(!next->context.pinned);
 
                /* stop flush ipis for the previous mm */
                clear_bit(cpu, &prev->cpu_vm_mask);
@@ -127,8 +126,11 @@ static inline void switch_mm(struct mm_s
        asm volatile("movl %0,%%fs"::"r"(0));  \
 } while(0)
 
-#define activate_mm(prev, next) do {           \
-       switch_mm((prev),(next),NULL);          \
-} while (0)
+static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
+{
+       if (!next->context.pinned)
+               mm_pin(next);
+       switch_mm(prev, next, NULL);
+}
 
 #endif
diff -r 5d4b9dc88218 -r 2fea03842f40 linux-2.6-xen-sparse/kernel/fork.c
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/linux-2.6-xen-sparse/kernel/fork.c        Tue Jun 13 15:56:28 2006 +0100
@@ -0,0 +1,1619 @@
+/*
+ *  linux/kernel/fork.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+/*
+ *  'fork.c' contains the help-routines for the 'fork' system call
+ * (see also entry.S and others).
+ * Fork is rather simple, once you get the hang of it, but the memory
+ * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
+ */
+
+#include <linux/config.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/unistd.h>
+#include <linux/smp_lock.h>
+#include <linux/module.h>
+#include <linux/vmalloc.h>
+#include <linux/completion.h>
+#include <linux/namespace.h>
+#include <linux/personality.h>
+#include <linux/mempolicy.h>
+#include <linux/sem.h>
+#include <linux/file.h>
+#include <linux/key.h>
+#include <linux/binfmts.h>
+#include <linux/mman.h>
+#include <linux/fs.h>
+#include <linux/capability.h>
+#include <linux/cpu.h>
+#include <linux/cpuset.h>
+#include <linux/security.h>
+#include <linux/swap.h>
+#include <linux/syscalls.h>
+#include <linux/jiffies.h>
+#include <linux/futex.h>
+#include <linux/rcupdate.h>
+#include <linux/ptrace.h>
+#include <linux/mount.h>
+#include <linux/audit.h>
+#include <linux/profile.h>
+#include <linux/rmap.h>
+#include <linux/acct.h>
+#include <linux/cn_proc.h>
+
+#include <asm/pgtable.h>
+#include <asm/pgalloc.h>
+#include <asm/uaccess.h>
+#include <asm/mmu_context.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+/*
+ * Protected counters by write_lock_irq(&tasklist_lock)
+ */
+unsigned long total_forks;     /* Handle normal Linux uptimes. */
+int nr_threads;                /* The idle threads do not count.. */
+
+int max_threads;               /* tunable limit on nr_threads */
+
+DEFINE_PER_CPU(unsigned long, process_counts) = 0;
+
+ __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
+
+EXPORT_SYMBOL(tasklist_lock);
+
+int nr_processes(void)
+{
+       int cpu;
+       int total = 0;
+
+       for_each_online_cpu(cpu)
+               total += per_cpu(process_counts, cpu);
+
+       return total;
+}
+
+#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
+# define alloc_task_struct()   kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
+# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
+static kmem_cache_t *task_struct_cachep;
+#endif
+
+/* SLAB cache for signal_struct structures (tsk->signal) */
+kmem_cache_t *signal_cachep;
+
+/* SLAB cache for sighand_struct structures (tsk->sighand) */
+kmem_cache_t *sighand_cachep;
+
+/* SLAB cache for files_struct structures (tsk->files) */
+kmem_cache_t *files_cachep;
+
+/* SLAB cache for fs_struct structures (tsk->fs) */
+kmem_cache_t *fs_cachep;
+
+/* SLAB cache for vm_area_struct structures */
+kmem_cache_t *vm_area_cachep;
+
+/* SLAB cache for mm_struct structures (tsk->mm) */
+static kmem_cache_t *mm_cachep;
+
+void free_task(struct task_struct *tsk)
+{
+       free_thread_info(tsk->thread_info);
+       free_task_struct(tsk);
+}
+EXPORT_SYMBOL(free_task);
+
+void __put_task_struct_cb(struct rcu_head *rhp)
+{
+       struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
+
+       WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
+       WARN_ON(atomic_read(&tsk->usage));
+       WARN_ON(tsk == current);
+
+       if (unlikely(tsk->audit_context))
+               audit_free(tsk);
+       security_task_free(tsk);
+       free_uid(tsk->user);
+       put_group_info(tsk->group_info);
+
+       if (!profile_handoff_task(tsk))
+               free_task(tsk);
+}
+
+void __init fork_init(unsigned long mempages)
+{
+#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
+#ifndef ARCH_MIN_TASKALIGN
+#define ARCH_MIN_TASKALIGN     L1_CACHE_BYTES
+#endif
+       /* create a slab on which task_structs can be allocated */
+       task_struct_cachep =
+               kmem_cache_create("task_struct", sizeof(struct task_struct),
+                       ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
+#endif
+
+       /*
+        * The default maximum number of threads is set to a safe
+        * value: the thread structures can take up at most half
+        * of memory.
+        */
+       max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
+
+       /*
+        * we need to allow at least 20 threads to boot a system
+        */
+       if(max_threads < 20)
+               max_threads = 20;
+
+       init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
+       init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
+       init_task.signal->rlim[RLIMIT_SIGPENDING] =
+               init_task.signal->rlim[RLIMIT_NPROC];
+}
+
+static struct task_struct *dup_task_struct(struct task_struct *orig)
+{
+       struct task_struct *tsk;
+       struct thread_info *ti;
+
+       prepare_to_copy(orig);
+
+       tsk = alloc_task_struct();
+       if (!tsk)
+               return NULL;
+
+       ti = alloc_thread_info(tsk);
+       if (!ti) {
+               free_task_struct(tsk);
+               return NULL;
+       }
+
+       *tsk = *orig;
+       tsk->thread_info = ti;
+       setup_thread_stack(tsk, orig);
+
+       /* One for us, one for whoever does the "release_task()" (usually 
parent) */
+       atomic_set(&tsk->usage,2);
+       atomic_set(&tsk->fs_excl, 0);
+       return tsk;
+}
+
+#ifdef CONFIG_MMU
+static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
+{
+       struct vm_area_struct *mpnt, *tmp, **pprev;
+       struct rb_node **rb_link, *rb_parent;
+       int retval;
+       unsigned long charge;
+       struct mempolicy *pol;
+
+       down_write(&oldmm->mmap_sem);
+       flush_cache_mm(oldmm);
+       down_write(&mm->mmap_sem);
+
+       mm->locked_vm = 0;
+       mm->mmap = NULL;
+       mm->mmap_cache = NULL;
+       mm->free_area_cache = oldmm->mmap_base;
+       mm->cached_hole_size = ~0UL;
+       mm->map_count = 0;
+       cpus_clear(mm->cpu_vm_mask);
+       mm->mm_rb = RB_ROOT;
+       rb_link = &mm->mm_rb.rb_node;
+       rb_parent = NULL;
+       pprev = &mm->mmap;
+
+       for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
+               struct file *file;
+
+               if (mpnt->vm_flags & VM_DONTCOPY) {
+                       long pages = vma_pages(mpnt);
+                       mm->total_vm -= pages;
+                       vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
+                                                               -pages);
+                       continue;
+               }
+               charge = 0;
+               if (mpnt->vm_flags & VM_ACCOUNT) {
+                       unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> 
PAGE_SHIFT;
+                       if (security_vm_enough_memory(len))
+                               goto fail_nomem;
+                       charge = len;
+               }
+               tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
+               if (!tmp)
+                       goto fail_nomem;
+               *tmp = *mpnt;
+               pol = mpol_copy(vma_policy(mpnt));
+               retval = PTR_ERR(pol);
+               if (IS_ERR(pol))
+                       goto fail_nomem_policy;
+               vma_set_policy(tmp, pol);
+               tmp->vm_flags &= ~VM_LOCKED;
+               tmp->vm_mm = mm;
+               tmp->vm_next = NULL;
+               anon_vma_link(tmp);
+               file = tmp->vm_file;
+               if (file) {
+                       struct inode *inode = file->f_dentry->d_inode;
+                       get_file(file);
+                       if (tmp->vm_flags & VM_DENYWRITE)
+                               atomic_dec(&inode->i_writecount);
+      
+                       /* insert tmp into the share list, just after mpnt */
+                       spin_lock(&file->f_mapping->i_mmap_lock);
+                       tmp->vm_truncate_count = mpnt->vm_truncate_count;
+                       flush_dcache_mmap_lock(file->f_mapping);
+                       vma_prio_tree_add(tmp, mpnt);
+                       flush_dcache_mmap_unlock(file->f_mapping);
+                       spin_unlock(&file->f_mapping->i_mmap_lock);
+               }
+
+               /*
+                * Link in the new vma and copy the page table entries.
+                */
+               *pprev = tmp;
+               pprev = &tmp->vm_next;
+
+               __vma_link_rb(mm, tmp, rb_link, rb_parent);
+               rb_link = &tmp->vm_rb.rb_right;
+               rb_parent = &tmp->vm_rb;
+
+               mm->map_count++;
+               retval = copy_page_range(mm, oldmm, mpnt);
+
+               if (tmp->vm_ops && tmp->vm_ops->open)
+                       tmp->vm_ops->open(tmp);
+
+               if (retval)
+                       goto out;
+       }
+#ifdef arch_dup_mmap
+       arch_dup_mmap(mm, oldmm);
+#endif
+       retval = 0;
+out:
+       up_write(&mm->mmap_sem);
+       flush_tlb_mm(oldmm);
+       up_write(&oldmm->mmap_sem);
+       return retval;
+fail_nomem_policy:
+       kmem_cache_free(vm_area_cachep, tmp);
+fail_nomem:
+       retval = -ENOMEM;
+       vm_unacct_memory(charge);
+       goto out;
+}
+
+static inline int mm_alloc_pgd(struct mm_struct * mm)
+{
+       mm->pgd = pgd_alloc(mm);
+       if (unlikely(!mm->pgd))
+               return -ENOMEM;
+       return 0;
+}
+
+static inline void mm_free_pgd(struct mm_struct * mm)
+{
+       pgd_free(mm->pgd);
+}
+#else
+#define dup_mmap(mm, oldmm)    (0)
+#define mm_alloc_pgd(mm)       (0)
+#define mm_free_pgd(mm)
+#endif /* CONFIG_MMU */
+
+ __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
+
+#define allocate_mm()  (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
+#define free_mm(mm)    (kmem_cache_free(mm_cachep, (mm)))
+
+#include <linux/init_task.h>
+
+static struct mm_struct * mm_init(struct mm_struct * mm)
+{
+       atomic_set(&mm->mm_users, 1);
+       atomic_set(&mm->mm_count, 1);
+       init_rwsem(&mm->mmap_sem);
+       INIT_LIST_HEAD(&mm->mmlist);
+       mm->core_waiters = 0;
+       mm->nr_ptes = 0;
+       set_mm_counter(mm, file_rss, 0);
+       set_mm_counter(mm, anon_rss, 0);
+       spin_lock_init(&mm->page_table_lock);
+       rwlock_init(&mm->ioctx_list_lock);
+       mm->ioctx_list = NULL;
+       mm->free_area_cache = TASK_UNMAPPED_BASE;
+       mm->cached_hole_size = ~0UL;
+
+       if (likely(!mm_alloc_pgd(mm))) {
+               mm->def_flags = 0;
+               return mm;
+       }
+       free_mm(mm);
+       return NULL;
+}
+
+/*
+ * Allocate and initialize an mm_struct.
+ */
+struct mm_struct * mm_alloc(void)
+{
+       struct mm_struct * mm;
+
+       mm = allocate_mm();
+       if (mm) {
+               memset(mm, 0, sizeof(*mm));
+               mm = mm_init(mm);
+       }
+       return mm;
+}
+
+/*
+ * Called when the last reference to the mm
+ * is dropped: either by a lazy thread or by
+ * mmput. Free the page directory and the mm.
+ */
+void fastcall __mmdrop(struct mm_struct *mm)
+{
+       BUG_ON(mm == &init_mm);
+       mm_free_pgd(mm);
+       destroy_context(mm);
+       free_mm(mm);
+}
+
+/*
+ * Decrement the use count and release all resources for an mm.
+ */
+void mmput(struct mm_struct *mm)
+{
+       if (atomic_dec_and_test(&mm->mm_users)) {
+               exit_aio(mm);
+               exit_mmap(mm);
+               if (!list_empty(&mm->mmlist)) {
+                       spin_lock(&mmlist_lock);
+                       list_del(&mm->mmlist);
+                       spin_unlock(&mmlist_lock);
+               }
+               put_swap_token(mm);
+               mmdrop(mm);
+       }
+}
+EXPORT_SYMBOL_GPL(mmput);
+
+/**
+ * get_task_mm - acquire a reference to the task's mm
+ *
+ * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
+ * this kernel workthread has transiently adopted a user mm with use_mm,
+ * to do its AIO) is not set and if so returns a reference to it, after
+ * bumping up the use count.  User must release the mm via mmput()
+ * after use.  Typically used by /proc and ptrace.
+ */
+struct mm_struct *get_task_mm(struct task_struct *task)
+{
+       struct mm_struct *mm;
+
+       task_lock(task);
+       mm = task->mm;
+       if (mm) {
+               if (task->flags & PF_BORROWED_MM)
+                       mm = NULL;
+               else
+                       atomic_inc(&mm->mm_users);
+       }
+       task_unlock(task);
+       return mm;
+}
+EXPORT_SYMBOL_GPL(get_task_mm);
+
+/* Please note the differences between mmput and mm_release.
+ * mmput is called whenever we stop holding onto a mm_struct,
+ * error success whatever.
+ *
+ * mm_release is called after a mm_struct has been removed
+ * from the current process.
+ *
+ * This difference is important for error handling, when we
+ * only half set up a mm_struct for a new process and need to restore
+ * the old one.  Because we mmput the new mm_struct before
+ * restoring the old one. . .
+ * Eric Biederman 10 January 1998
+ */
+void mm_release(struct task_struct *tsk, struct mm_struct *mm)
+{
+       struct completion *vfork_done = tsk->vfork_done;
+
+       /* Get rid of any cached register state */
+       deactivate_mm(tsk, mm);
+
+       /* notify parent sleeping on vfork() */
+       if (vfork_done) {
+               tsk->vfork_done = NULL;
+               complete(vfork_done);
+       }
+       if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
+               u32 __user * tidptr = tsk->clear_child_tid;
+               tsk->clear_child_tid = NULL;
+
+               /*
+                * We don't check the error code - if userspace has
+                * not set up a proper pointer then tough luck.
+                */
+               put_user(0, tidptr);
+               sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
+       }
+}
+
+/*
+ * Allocate a new mm structure and copy contents from the
+ * mm structure of the passed in task structure.
+ */
+static struct mm_struct *dup_mm(struct task_struct *tsk)
+{
+       struct mm_struct *mm, *oldmm = current->mm;
+       int err;
+
+       if (!oldmm)
+               return NULL;
+
+       mm = allocate_mm();
+       if (!mm)
+               goto fail_nomem;
+
+       memcpy(mm, oldmm, sizeof(*mm));
+
+       if (!mm_init(mm))
+               goto fail_nomem;
+
+       if (init_new_context(tsk, mm))
+               goto fail_nocontext;
+
+       err = dup_mmap(mm, oldmm);
+       if (err)
+               goto free_pt;
+
+       mm->hiwater_rss = get_mm_rss(mm);
+       mm->hiwater_vm = mm->total_vm;
+
+       return mm;
+
+free_pt:
+       mmput(mm);
+
+fail_nomem:
+       return NULL;
+
+fail_nocontext:
+       /*
+        * If init_new_context() failed, we cannot use mmput() to free the mm
+        * because it calls destroy_context()
+        */
+       mm_free_pgd(mm);
+       free_mm(mm);
+       return NULL;
+}
+
+static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
+{
+       struct mm_struct * mm, *oldmm;
+       int retval;
+
+       tsk->min_flt = tsk->maj_flt = 0;
+       tsk->nvcsw = tsk->nivcsw = 0;
+
+       tsk->mm = NULL;
+       tsk->active_mm = NULL;
+
+       /*
+        * Are we cloning a kernel thread?
+        *
+        * We need to steal a active VM for that..
+        */
+       oldmm = current->mm;
+       if (!oldmm)
+               return 0;
+
+       if (clone_flags & CLONE_VM) {
+               atomic_inc(&oldmm->mm_users);
+               mm = oldmm;
+               goto good_mm;
+       }
+
+       retval = -ENOMEM;
+       mm = dup_mm(tsk);
+       if (!mm)
+               goto fail_nomem;
+
+good_mm:
+       tsk->mm = mm;
+       tsk->active_mm = mm;
+       return 0;
+
+fail_nomem:
+       return retval;
+}
+
+static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
+{
+       struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
+       /* We don't need to lock fs - think why ;-) */
+       if (fs) {
+               atomic_set(&fs->count, 1);
+               rwlock_init(&fs->lock);
+               fs->umask = old->umask;
+               read_lock(&old->lock);
+               fs->rootmnt = mntget(old->rootmnt);
+               fs->root = dget(old->root);
+               fs->pwdmnt = mntget(old->pwdmnt);
+               fs->pwd = dget(old->pwd);
+               if (old->altroot) {
+                       fs->altrootmnt = mntget(old->altrootmnt);
+                       fs->altroot = dget(old->altroot);
+               } else {
+                       fs->altrootmnt = NULL;
+                       fs->altroot = NULL;
+               }
+               read_unlock(&old->lock);
+       }
+       return fs;
+}
+
+struct fs_struct *copy_fs_struct(struct fs_struct *old)
+{
+       return __copy_fs_struct(old);
+}
+
+EXPORT_SYMBOL_GPL(copy_fs_struct);
+
+static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
+{
+       if (clone_flags & CLONE_FS) {
+               atomic_inc(&current->fs->count);
+               return 0;
+       }
+       tsk->fs = __copy_fs_struct(current->fs);
+       if (!tsk->fs)
+               return -ENOMEM;
+       return 0;
+}
+
+static int count_open_files(struct fdtable *fdt)
+{
+       int size = fdt->max_fdset;
+       int i;
+
+       /* Find the last open fd */
+       for (i = size/(8*sizeof(long)); i > 0; ) {
+               if (fdt->open_fds->fds_bits[--i])
+                       break;
+       }
+       i = (i+1) * 8 * sizeof(long);
+       return i;
+}
+
+static struct files_struct *alloc_files(void)
+{
+       struct files_struct *newf;
+       struct fdtable *fdt;
+
+       newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
+       if (!newf)
+               goto out;
+
+       atomic_set(&newf->count, 1);
+
+       spin_lock_init(&newf->file_lock);
+       fdt = &newf->fdtab;
+       fdt->next_fd = 0;
+       fdt->max_fds = NR_OPEN_DEFAULT;
+       fdt->max_fdset = __FD_SETSIZE;
+       fdt->close_on_exec = &newf->close_on_exec_init;
+       fdt->open_fds = &newf->open_fds_init;
+       fdt->fd = &newf->fd_array[0];
+       INIT_RCU_HEAD(&fdt->rcu);
+       fdt->free_files = NULL;
+       fdt->next = NULL;
+       rcu_assign_pointer(newf->fdt, fdt);
+out:
+       return newf;
+}
+
+/*
+ * Allocate a new files structure and copy contents from the
+ * passed in files structure.
+ */
+static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
+{
+       struct files_struct *newf;
+       struct file **old_fds, **new_fds;
+       int open_files, size, i, expand;
+       struct fdtable *old_fdt, *new_fdt;
+
+       newf = alloc_files();
+       if (!newf)
+               goto out;
+
+       spin_lock(&oldf->file_lock);
+       old_fdt = files_fdtable(oldf);
+       new_fdt = files_fdtable(newf);
+       size = old_fdt->max_fdset;
+       open_files = count_open_files(old_fdt);
+       expand = 0;
+
+       /*
+        * Check whether we need to allocate a larger fd array or fd set.
+        * Note: we're not a clone task, so the open count won't  change.
+        */
+       if (open_files > new_fdt->max_fdset) {
+               new_fdt->max_fdset = 0;
+               expand = 1;
+       }
+       if (open_files > new_fdt->max_fds) {
+               new_fdt->max_fds = 0;
+               expand = 1;
+       }
+
+       /* if the old fdset gets grown now, we'll only copy up to "size" fds */
+       if (expand) {
+               spin_unlock(&oldf->file_lock);
+               spin_lock(&newf->file_lock);
+               *errorp = expand_files(newf, open_files-1);
+               spin_unlock(&newf->file_lock);
+               if (*errorp < 0)
+                       goto out_release;
+               new_fdt = files_fdtable(newf);
+               /*
+                * Reacquire the oldf lock and a pointer to its fd table
+                * who knows it may have a new bigger fd table. We need
+                * the latest pointer.
+                */
+               spin_lock(&oldf->file_lock);
+               old_fdt = files_fdtable(oldf);
+       }
+
+       old_fds = old_fdt->fd;
+       new_fds = new_fdt->fd;
+
+       memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, 
open_files/8);
+       memcpy(new_fdt->close_on_exec->fds_bits, 
old_fdt->close_on_exec->fds_bits, open_files/8);
+
+       for (i = open_files; i != 0; i--) {
+               struct file *f = *old_fds++;
+               if (f) {
+                       get_file(f);
+               } else {
+                       /*
+                        * The fd may be claimed in the fd bitmap but not yet
+                        * instantiated in the files array if a sibling thread
+                        * is partway through open().  So make sure that this
+                        * fd is available to the new process.
+                        */
+                       FD_CLR(open_files - i, new_fdt->open_fds);
+               }
+               rcu_assign_pointer(*new_fds++, f);
+       }
+       spin_unlock(&oldf->file_lock);
+
+       /* compute the remainder to be cleared */
+       size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
+
+       /* This is long word aligned thus could use a optimized version */ 
+       memset(new_fds, 0, size); 
+
+       if (new_fdt->max_fdset > open_files) {
+               int left = (new_fdt->max_fdset-open_files)/8;
+               int start = open_files / (8 * sizeof(unsigned long));
+
+               memset(&new_fdt->open_fds->fds_bits[start], 0, left);
+               memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
+       }
+
+out:
+       return newf;
+
+out_release:
+       free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
+       free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
+       free_fd_array(new_fdt->fd, new_fdt->max_fds);
+       kmem_cache_free(files_cachep, newf);
+       return NULL;
+}
+
+static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
+{
+       struct files_struct *oldf, *newf;
+       int error = 0;
+
+       /*
+        * A background process may not have any files ...
+        */
+       oldf = current->files;
+       if (!oldf)
+               goto out;
+
+       if (clone_flags & CLONE_FILES) {
+               atomic_inc(&oldf->count);
+               goto out;
+       }
+
+       /*
+        * Note: we may be using current for both targets (See exec.c)
+        * This works because we cache current->files (old) as oldf. Don't
+        * break this.
+        */
+       tsk->files = NULL;
+       error = -ENOMEM;
+       newf = dup_fd(oldf, &error);
+       if (!newf)
+               goto out;
+
+       tsk->files = newf;
+       error = 0;
+out:
+       return error;
+}
+
+/*
+ *     Helper to unshare the files of the current task.
+ *     We don't want to expose copy_files internals to
+ *     the exec layer of the kernel.
+ */
+
+int unshare_files(void)
+{
+       struct files_struct *files  = current->files;
+       int rc;
+
+       if(!files)
+               BUG();
+
+       /* This can race but the race causes us to copy when we don't
+          need to and drop the copy */
+       if(atomic_read(&files->count) == 1)
+       {
+               atomic_inc(&files->count);
+               return 0;
+       }
+       rc = copy_files(0, current);
+       if(rc)
+               current->files = files;
+       return rc;
+}
+
+EXPORT_SYMBOL(unshare_files);
+
+void sighand_free_cb(struct rcu_head *rhp)
+{
+       struct sighand_struct *sp;
+
+       sp = container_of(rhp, struct sighand_struct, rcu);
+       kmem_cache_free(sighand_cachep, sp);
+}
+
+static inline int copy_sighand(unsigned long clone_flags, struct task_struct * 
tsk)
+{
+       struct sighand_struct *sig;
+
+       if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
+               atomic_inc(&current->sighand->count);
+               return 0;
+       }
+       sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
+       rcu_assign_pointer(tsk->sighand, sig);
+       if (!sig)
+               return -ENOMEM;
+       spin_lock_init(&sig->siglock);
+       atomic_set(&sig->count, 1);
+       memcpy(sig->action, current->sighand->action, sizeof(sig->action));
+       return 0;
+}
+
+static inline int copy_signal(unsigned long clone_flags, struct task_struct * 
tsk)
+{
+       struct signal_struct *sig;
+       int ret;
+
+       if (clone_flags & CLONE_THREAD) {
+               atomic_inc(&current->signal->count);
+               atomic_inc(&current->signal->live);
+               return 0;
+       }
+       sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
+       tsk->signal = sig;
+       if (!sig)
+               return -ENOMEM;
+
+       ret = copy_thread_group_keys(tsk);
+       if (ret < 0) {
+               kmem_cache_free(signal_cachep, sig);
+               return ret;
+       }
+
+       atomic_set(&sig->count, 1);
+       atomic_set(&sig->live, 1);
+       init_waitqueue_head(&sig->wait_chldexit);
+       sig->flags = 0;
+       sig->group_exit_code = 0;
+       sig->group_exit_task = NULL;
+       sig->group_stop_count = 0;
+       sig->curr_target = NULL;
+       init_sigpending(&sig->shared_pending);
+       INIT_LIST_HEAD(&sig->posix_timers);
+
+       hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
+       sig->it_real_incr.tv64 = 0;
+       sig->real_timer.function = it_real_fn;
+       sig->real_timer.data = tsk;
+
+       sig->it_virt_expires = cputime_zero;
+       sig->it_virt_incr = cputime_zero;
+       sig->it_prof_expires = cputime_zero;
+       sig->it_prof_incr = cputime_zero;
+
+       sig->leader = 0;        /* session leadership doesn't inherit */
+       sig->tty_old_pgrp = 0;
+
+       sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
+       sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
+       sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
+       sig->sched_time = 0;
+       INIT_LIST_HEAD(&sig->cpu_timers[0]);
+       INIT_LIST_HEAD(&sig->cpu_timers[1]);
+       INIT_LIST_HEAD(&sig->cpu_timers[2]);
+
+       task_lock(current->group_leader);
+       memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
+       task_unlock(current->group_leader);
+
+       if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
+               /*
+                * New sole thread in the process gets an expiry time
+                * of the whole CPU time limit.
+                */
+               tsk->it_prof_expires =
+                       secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
+       }
+
+       return 0;
+}
+
+static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
+{
+       unsigned long new_flags = p->flags;
+
+       new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
+       new_flags |= PF_FORKNOEXEC;
+       if (!(clone_flags & CLONE_PTRACE))
+               p->ptrace = 0;
+       p->flags = new_flags;
+}
+
+asmlinkage long sys_set_tid_address(int __user *tidptr)
+{
+       current->clear_child_tid = tidptr;
+
+       return current->pid;
+}
+
+/*
+ * This creates a new process as a copy of the old one,
+ * but does not actually start it yet.
+ *
+ * It copies the registers, and all the appropriate
+ * parts of the process environment (as per the clone
+ * flags). The actual kick-off is left to the caller.
+ */
+static task_t *copy_process(unsigned long clone_flags,
+                                unsigned long stack_start,
+                                struct pt_regs *regs,
+                                unsigned long stack_size,
+                                int __user *parent_tidptr,
+                                int __user *child_tidptr,
+                                int pid)
+{
+       int retval;
+       struct task_struct *p = NULL;
+
+       if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
+               return ERR_PTR(-EINVAL);
+
+       /*
+        * Thread groups must share signals as well, and detached threads
+        * can only be started up within the thread group.
+        */
+       if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
+               return ERR_PTR(-EINVAL);
+
+       /*
+        * Shared signal handlers imply shared VM. By way of the above,
+        * thread groups also imply shared VM. Blocking this case allows
+        * for various simplifications in other code.
+        */
+       if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
+               return ERR_PTR(-EINVAL);
+
+       retval = security_task_create(clone_flags);
+       if (retval)
+               goto fork_out;
+
+       retval = -ENOMEM;
+       p = dup_task_struct(current);
+       if (!p)
+               goto fork_out;
+
+       retval = -EAGAIN;
+       if (atomic_read(&p->user->processes) >=
+                       p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
+               if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
+                               p->user != &root_user)
+                       goto bad_fork_free;
+       }
+
+       atomic_inc(&p->user->__count);
+       atomic_inc(&p->user->processes);
+       get_group_info(p->group_info);
+
+       /*
+        * If multiple threads are within copy_process(), then this check
+        * triggers too late. This doesn't hurt, the check is only there
+        * to stop root fork bombs.
+        */
+       if (nr_threads >= max_threads)
+               goto bad_fork_cleanup_count;
+
+       if (!try_module_get(task_thread_info(p)->exec_domain->module))
+               goto bad_fork_cleanup_count;
+
+       if (p->binfmt && !try_module_get(p->binfmt->module))
+               goto bad_fork_cleanup_put_domain;
+
+       p->did_exec = 0;
+       copy_flags(clone_flags, p);
+       p->pid = pid;
+       retval = -EFAULT;
+       if (clone_flags & CLONE_PARENT_SETTID)
+               if (put_user(p->pid, parent_tidptr))
+                       goto bad_fork_cleanup;
+
+       p->proc_dentry = NULL;
+
+       INIT_LIST_HEAD(&p->children);
+       INIT_LIST_HEAD(&p->sibling);
+       p->vfork_done = NULL;
+       spin_lock_init(&p->alloc_lock);
+       spin_lock_init(&p->proc_lock);
+
+       clear_tsk_thread_flag(p, TIF_SIGPENDING);
+       init_sigpending(&p->pending);
+
+       p->utime = cputime_zero;
+       p->stime = cputime_zero;
+       p->sched_time = 0;
+       p->rchar = 0;           /* I/O counter: bytes read */
+       p->wchar = 0;           /* I/O counter: bytes written */
+       p->syscr = 0;           /* I/O counter: read syscalls */
+       p->syscw = 0;           /* I/O counter: write syscalls */
+       acct_clear_integrals(p);
+
+       p->it_virt_expires = cputime_zero;
+       p->it_prof_expires = cputime_zero;
+       p->it_sched_expires = 0;
+       INIT_LIST_HEAD(&p->cpu_timers[0]);
+       INIT_LIST_HEAD(&p->cpu_timers[1]);
+       INIT_LIST_HEAD(&p->cpu_timers[2]);
+
+       p->lock_depth = -1;             /* -1 = no lock */
+       do_posix_clock_monotonic_gettime(&p->start_time);
+       p->security = NULL;
+       p->io_context = NULL;
+       p->io_wait = NULL;
+       p->audit_context = NULL;
+       cpuset_fork(p);
+#ifdef CONFIG_NUMA
+       p->mempolicy = mpol_copy(p->mempolicy);
+       if (IS_ERR(p->mempolicy)) {
+               retval = PTR_ERR(p->mempolicy);
+               p->mempolicy = NULL;
+               goto bad_fork_cleanup_cpuset;
+       }
+#endif
+
+#ifdef CONFIG_DEBUG_MUTEXES
+       p->blocked_on = NULL; /* not blocked yet */
+#endif
+
+       p->tgid = p->pid;
+       if (clone_flags & CLONE_THREAD)
+               p->tgid = current->tgid;
+
+       if ((retval = security_task_alloc(p)))
+               goto bad_fork_cleanup_policy;
+       if ((retval = audit_alloc(p)))
+               goto bad_fork_cleanup_security;
+       /* copy all the process information */
+       if ((retval = copy_semundo(clone_flags, p)))
+               goto bad_fork_cleanup_audit;
+       if ((retval = copy_files(clone_flags, p)))
+               goto bad_fork_cleanup_semundo;
+       if ((retval = copy_fs(clone_flags, p)))
+               goto bad_fork_cleanup_files;
+       if ((retval = copy_sighand(clone_flags, p)))
+               goto bad_fork_cleanup_fs;
+       if ((retval = copy_signal(clone_flags, p)))
+               goto bad_fork_cleanup_sighand;
+       if ((retval = copy_mm(clone_flags, p)))
+               goto bad_fork_cleanup_signal;
+       if ((retval = copy_keys(clone_flags, p)))
+               goto bad_fork_cleanup_mm;
+       if ((retval = copy_namespace(clone_flags, p)))
+               goto bad_fork_cleanup_keys;
+       retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
+       if (retval)
+               goto bad_fork_cleanup_namespace;
+
+       p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : 
NULL;
+       /*
+        * Clear TID on mm_release()?
+        */
+       p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? 
child_tidptr: NULL;
+
+       /*
+        * sigaltstack should be cleared when sharing the same VM
+        */
+       if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
+               p->sas_ss_sp = p->sas_ss_size = 0;
+
+       /*
+        * Syscall tracing should be turned off in the child regardless
+        * of CLONE_PTRACE.
+        */
+       clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
+#ifdef TIF_SYSCALL_EMU
+       clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
+#endif
+
+       /* Our parent execution domain becomes current domain
+          These must match for thread signalling to apply */
+          
+       p->parent_exec_id = p->self_exec_id;
+
+       /* ok, now we should be set up.. */
+       p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & 
CSIGNAL);
+       p->pdeath_signal = 0;
+       p->exit_state = 0;
+
+       /*
+        * Ok, make it visible to the rest of the system.
+        * We dont wake it up yet.
+        */
+       p->group_leader = p;
+       INIT_LIST_HEAD(&p->ptrace_children);
+       INIT_LIST_HEAD(&p->ptrace_list);
+
+       /* Perform scheduler related setup. Assign this task to a CPU. */
+       sched_fork(p, clone_flags);
+
+       /* Need tasklist lock for parent etc handling! */
+       write_lock_irq(&tasklist_lock);
+
+       /*
+        * The task hasn't been attached yet, so its cpus_allowed mask will
+        * not be changed, nor will its assigned CPU.
+        *
+        * The cpus_allowed mask of the parent may have changed after it was
+        * copied first time - so re-copy it here, then check the child's CPU
+        * to ensure it is on a valid CPU (and if not, just force it back to
+        * parent's CPU). This avoids alot of nasty races.
+        */
+       p->cpus_allowed = current->cpus_allowed;
+       if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
+                       !cpu_online(task_cpu(p))))
+               set_task_cpu(p, smp_processor_id());
+
+       /*
+        * Check for pending SIGKILL! The new thread should not be allowed
+        * to slip out of an OOM kill. (or normal SIGKILL.)
+        */
+       if (sigismember(&current->pending.signal, SIGKILL)) {
+               write_unlock_irq(&tasklist_lock);
+               retval = -EINTR;
+               goto bad_fork_cleanup_namespace;
+       }
+
+       /* CLONE_PARENT re-uses the old parent */
+       if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
+               p->real_parent = current->real_parent;
+       else
+               p->real_parent = current;
+       p->parent = p->real_parent;
+
+       spin_lock(&current->sighand->siglock);
+       if (clone_flags & CLONE_THREAD) {
+               /*
+                * Important: if an exit-all has been started then
+                * do not create this new thread - the whole thread
+                * group is supposed to exit anyway.
+                */
+               if (current->signal->flags & SIGNAL_GROUP_EXIT) {
+                       spin_unlock(&current->sighand->siglock);
+                       write_unlock_irq(&tasklist_lock);
+                       retval = -EAGAIN;
+                       goto bad_fork_cleanup_namespace;
+               }
+               p->group_leader = current->group_leader;
+
+               if (current->signal->group_stop_count > 0) {
+                       /*
+                        * There is an all-stop in progress for the group.
+                        * We ourselves will stop as soon as we check signals.
+                        * Make the new thread part of that group stop too.
+                        */
+                       current->signal->group_stop_count++;
+                       set_tsk_thread_flag(p, TIF_SIGPENDING);
+               }
+
+               if (!cputime_eq(current->signal->it_virt_expires,
+                               cputime_zero) ||
+                   !cputime_eq(current->signal->it_prof_expires,
+                               cputime_zero) ||
+                   current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY 
||
+                   !list_empty(&current->signal->cpu_timers[0]) ||
+                   !list_empty(&current->signal->cpu_timers[1]) ||
+                   !list_empty(&current->signal->cpu_timers[2])) {
+                       /*
+                        * Have child wake up on its first tick to check
+                        * for process CPU timers.
+                        */
+                       p->it_prof_expires = jiffies_to_cputime(1);
+               }
+       }
+
+       /*
+        * inherit ioprio
+        */
+       p->ioprio = current->ioprio;
+
+       SET_LINKS(p);
+       if (unlikely(p->ptrace & PT_PTRACED))
+               __ptrace_link(p, current->parent);
+
+       if (thread_group_leader(p)) {
+               p->signal->tty = current->signal->tty;
+               p->signal->pgrp = process_group(current);
+               p->signal->session = current->signal->session;
+               attach_pid(p, PIDTYPE_PGID, process_group(p));
+               attach_pid(p, PIDTYPE_SID, p->signal->session);
+               if (p->pid)
+                       __get_cpu_var(process_counts)++;
+       }
+       attach_pid(p, PIDTYPE_TGID, p->tgid);
+       attach_pid(p, PIDTYPE_PID, p->pid);
+
+       nr_threads++;
+       total_forks++;
+       spin_unlock(&current->sighand->siglock);
+       write_unlock_irq(&tasklist_lock);
+       proc_fork_connector(p);
+       return p;
+
+bad_fork_cleanup_namespace:
+       exit_namespace(p);
+bad_fork_cleanup_keys:
+       exit_keys(p);
+bad_fork_cleanup_mm:
+       if (p->mm)
+               mmput(p->mm);
+bad_fork_cleanup_signal:
+       exit_signal(p);
+bad_fork_cleanup_sighand:
+       exit_sighand(p);
+bad_fork_cleanup_fs:
+       exit_fs(p); /* blocking */
+bad_fork_cleanup_files:
+       exit_files(p); /* blocking */
+bad_fork_cleanup_semundo:
+       exit_sem(p);
+bad_fork_cleanup_audit:
+       audit_free(p);
+bad_fork_cleanup_security:
+       security_task_free(p);
+bad_fork_cleanup_policy:
+#ifdef CONFIG_NUMA
+       mpol_free(p->mempolicy);
+bad_fork_cleanup_cpuset:
+#endif
+       cpuset_exit(p);
+bad_fork_cleanup:
+       if (p->binfmt)
+               module_put(p->binfmt->module);
+bad_fork_cleanup_put_domain:
+       module_put(task_thread_info(p)->exec_domain->module);
+bad_fork_cleanup_count:
+       put_group_info(p->group_info);
+       atomic_dec(&p->user->processes);
+       free_uid(p->user);
+bad_fork_free:
+       free_task(p);
+fork_out:
+       return ERR_PTR(retval);
+}
+
+struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs 
*regs)
+{
+       memset(regs, 0, sizeof(struct pt_regs));
+       return regs;
+}
+
+task_t * __devinit fork_idle(int cpu)
+{
+       task_t *task;
+       struct pt_regs regs;
+
+       task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
+       if (!task)
+               return ERR_PTR(-ENOMEM);
+       init_idle(task, cpu);
+       unhash_process(task);
+       return task;
+}
+
+static inline int fork_traceflag (unsigned clone_flags)
+{
+       if (clone_flags & CLONE_UNTRACED)
+               return 0;
+       else if (clone_flags & CLONE_VFORK) {
+               if (current->ptrace & PT_TRACE_VFORK)
+                       return PTRACE_EVENT_VFORK;
+       } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
+               if (current->ptrace & PT_TRACE_CLONE)
+                       return PTRACE_EVENT_CLONE;
+       } else if (current->ptrace & PT_TRACE_FORK)
+               return PTRACE_EVENT_FORK;
+
+       return 0;
+}
+
+/*
+ *  Ok, this is the main fork-routine.
+ *
+ * It copies the process, and if successful kick-starts
+ * it and waits for it to finish using the VM if required.
+ */
+long do_fork(unsigned long clone_flags,
+             unsigned long stack_start,
+             struct pt_regs *regs,
+             unsigned long stack_size,
+             int __user *parent_tidptr,
+             int __user *child_tidptr)
+{
+       struct task_struct *p;
+       int trace = 0;
+       long pid = alloc_pidmap();
+
+       if (pid < 0)
+               return -EAGAIN;
+       if (unlikely(current->ptrace)) {
+               trace = fork_traceflag (clone_flags);
+               if (trace)
+                       clone_flags |= CLONE_PTRACE;
+       }
+
+       p = copy_process(clone_flags, stack_start, regs, stack_size, 
parent_tidptr, child_tidptr, pid);
+       /*
+        * Do this prior waking up the new thread - the thread pointer
+        * might get invalid after that point, if the thread exits quickly.
+        */
+       if (!IS_ERR(p)) {
+               struct completion vfork;
+
+               if (clone_flags & CLONE_VFORK) {
+                       p->vfork_done = &vfork;
+                       init_completion(&vfork);
+               }
+
+               if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
+                       /*
+                        * We'll start up with an immediate SIGSTOP.
+                        */
+                       sigaddset(&p->pending.signal, SIGSTOP);
+                       set_tsk_thread_flag(p, TIF_SIGPENDING);
+               }
+
+               if (!(clone_flags & CLONE_STOPPED))
+                       wake_up_new_task(p, clone_flags);
+               else
+                       p->state = TASK_STOPPED;
+
+               if (unlikely (trace)) {
+                       current->ptrace_message = pid;
+                       ptrace_notify ((trace << 8) | SIGTRAP);
+               }
+
+               if (clone_flags & CLONE_VFORK) {
+                       wait_for_completion(&vfork);
+                       if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
+                               ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | 
SIGTRAP);
+               }
+       } else {
+               free_pidmap(pid);
+               pid = PTR_ERR(p);
+       }
+       return pid;
+}
+
+#ifndef ARCH_MIN_MMSTRUCT_ALIGN
+#define ARCH_MIN_MMSTRUCT_ALIGN 0
+#endif
+
+void __init proc_caches_init(void)
+{
+       sighand_cachep = kmem_cache_create("sighand_cache",
+                       sizeof(struct sighand_struct), 0,
+                       SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+       signal_cachep = kmem_cache_create("signal_cache",
+                       sizeof(struct signal_struct), 0,
+                       SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+       files_cachep = kmem_cache_create("files_cache", 
+                       sizeof(struct files_struct), 0,
+                       SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+       fs_cachep = kmem_cache_create("fs_cache", 
+                       sizeof(struct fs_struct), 0,
+                       SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+       vm_area_cachep = kmem_cache_create("vm_area_struct",
+                       sizeof(struct vm_area_struct), 0,
+                       SLAB_PANIC, NULL, NULL);
+       mm_cachep = kmem_cache_create("mm_struct",
+                       sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
+                       SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
+}
+
+
+/*
+ * Check constraints on flags passed to the unshare system call and
+ * force unsharing of additional process context as appropriate.
+ */
+static inline void check_unshare_flags(unsigned long *flags_ptr)
+{
+       /*
+        * If unsharing a thread from a thread group, must also
+        * unshare vm.
+        */
+       if (*flags_ptr & CLONE_THREAD)
+               *flags_ptr |= CLONE_VM;
+
+       /*
+        * If unsharing vm, must also unshare signal handlers.
+        */
+       if (*flags_ptr & CLONE_VM)
+               *flags_ptr |= CLONE_SIGHAND;
+
+       /*
+        * If unsharing signal handlers and the task was created
+        * using CLONE_THREAD, then must unshare the thread
+        */
+       if ((*flags_ptr & CLONE_SIGHAND) &&
+           (atomic_read(&current->signal->count) > 1))
+               *flags_ptr |= CLONE_THREAD;
+
+       /*
+        * If unsharing namespace, must also unshare filesystem information.
+        */
+       if (*flags_ptr & CLONE_NEWNS)
+               *flags_ptr |= CLONE_FS;
+}
+
+/*
+ * Unsharing of tasks created with CLONE_THREAD is not supported yet
+ */
+static int unshare_thread(unsigned long unshare_flags)
+{
+       if (unshare_flags & CLONE_THREAD)
+               return -EINVAL;
+
+       return 0;
+}
+
+/*
+ * Unshare the filesystem structure if it is being shared
+ */
+static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
+{
+       struct fs_struct *fs = current->fs;
+
+       if ((unshare_flags & CLONE_FS) &&
+           (fs && atomic_read(&fs->count) > 1)) {
+               *new_fsp = __copy_fs_struct(current->fs);
+               if (!*new_fsp)
+                       return -ENOMEM;
+       }
+
+       return 0;
+}
+
+/*
+ * Unshare the namespace structure if it is being shared
+ */
+static int unshare_namespace(unsigned long unshare_flags, struct namespace 
**new_nsp, struct fs_struct *new_fs)
+{
+       struct namespace *ns = current->namespace;
+
+       if ((unshare_flags & CLONE_NEWNS) &&
+           (ns && atomic_read(&ns->count) > 1)) {
+               if (!capable(CAP_SYS_ADMIN))
+                       return -EPERM;
+
+               *new_nsp = dup_namespace(current, new_fs ? new_fs : 
current->fs);
+               if (!*new_nsp)
+                       return -ENOMEM;
+       }
+
+       return 0;
+}
+
+/*
+ * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
+ * supported yet
+ */
+static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct 
**new_sighp)
+{
+       struct sighand_struct *sigh = current->sighand;
+
+       if ((unshare_flags & CLONE_SIGHAND) &&
+           (sigh && atomic_read(&sigh->count) > 1))
+               return -EINVAL;
+       else
+               return 0;
+}
+
+/*
+ * Unshare vm if it is being shared
+ */
+static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
+{
+       struct mm_struct *mm = current->mm;
+
+       if ((unshare_flags & CLONE_VM) &&
+           (mm && atomic_read(&mm->mm_users) > 1)) {
+               return -EINVAL;
+       }
+
+       return 0;
+}
+
+/*
+ * Unshare file descriptor table if it is being shared
+ */
+static int unshare_fd(unsigned long unshare_flags, struct files_struct 
**new_fdp)
+{
+       struct files_struct *fd = current->files;
+       int error = 0;
+
+       if ((unshare_flags & CLONE_FILES) &&
+           (fd && atomic_read(&fd->count) > 1)) {
+               *new_fdp = dup_fd(fd, &error);
+               if (!*new_fdp)
+                       return error;
+       }
+
+       return 0;
+}
+
+/*
+ * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
+ * supported yet
+ */
+static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list 
**new_ulistp)
+{
+       if (unshare_flags & CLONE_SYSVSEM)
+               return -EINVAL;
+
+       return 0;
+}
+
+/*
+ * unshare allows a process to 'unshare' part of the process
+ * context which was originally shared using clone.  copy_*
+ * functions used by do_fork() cannot be used here directly
+ * because they modify an inactive task_struct that is being
+ * constructed. Here we are modifying the current, active,
+ * task_struct.
+ */
+asmlinkage long sys_unshare(unsigned long unshare_flags)
+{
+       int err = 0;
+       struct fs_struct *fs, *new_fs = NULL;
+       struct namespace *ns, *new_ns = NULL;
+       struct sighand_struct *sigh, *new_sigh = NULL;
+       struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
+       struct files_struct *fd, *new_fd = NULL;
+       struct sem_undo_list *new_ulist = NULL;
+
+       check_unshare_flags(&unshare_flags);
+
+       if ((err = unshare_thread(unshare_flags)))
+               goto bad_unshare_out;
+       if ((err = unshare_fs(unshare_flags, &new_fs)))
+               goto bad_unshare_cleanup_thread;
+       if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
+               goto bad_unshare_cleanup_fs;
+       if ((err = unshare_sighand(unshare_flags, &new_sigh)))
+               goto bad_unshare_cleanup_ns;
+       if ((err = unshare_vm(unshare_flags, &new_mm)))
+               goto bad_unshare_cleanup_sigh;
+       if ((err = unshare_fd(unshare_flags, &new_fd)))
+               goto bad_unshare_cleanup_vm;
+       if ((err = unshare_semundo(unshare_flags, &new_ulist)))
+               goto bad_unshare_cleanup_fd;
+
+       if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
+
+               task_lock(current);
+
+               if (new_fs) {
+                       fs = current->fs;
+                       current->fs = new_fs;
+                       new_fs = fs;
+               }
+
+               if (new_ns) {
+                       ns = current->namespace;
+                       current->namespace = new_ns;
+                       new_ns = ns;
+               }
+
+               if (new_sigh) {
+                       sigh = current->sighand;
+                       rcu_assign_pointer(current->sighand, new_sigh);
+                       new_sigh = sigh;
+               }
+
+               if (new_mm) {
+                       mm = current->mm;
+                       active_mm = current->active_mm;
+                       current->mm = new_mm;
+                       current->active_mm = new_mm;
+                       activate_mm(active_mm, new_mm);
+                       new_mm = mm;
+               }
+
+               if (new_fd) {
+                       fd = current->files;
+                       current->files = new_fd;
+                       new_fd = fd;
+               }
+
+               task_unlock(current);
+       }
+
+bad_unshare_cleanup_fd:
+       if (new_fd)
+               put_files_struct(new_fd);
+
+bad_unshare_cleanup_vm:
+       if (new_mm)
+               mmput(new_mm);
+
+bad_unshare_cleanup_sigh:
+       if (new_sigh)
+               if (atomic_dec_and_test(&new_sigh->count))
+                       kmem_cache_free(sighand_cachep, new_sigh);
+
+bad_unshare_cleanup_ns:
+       if (new_ns)
+               put_namespace(new_ns);
+
+bad_unshare_cleanup_fs:
+       if (new_fs)
+               put_fs_struct(new_fs);
+
+bad_unshare_cleanup_thread:
+bad_unshare_out:
+       return err;
+}

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