# HG changeset patch
# User Andrew Warfield <andy@xxxxxxxxxxxxx>
# Date 1159470181 25200
# Node ID 5f5e3b4c6fba7c56df9bc7c29236ba2ae9a9d2a1
# Parent 460f2c954cca7b28e2db89b72cc6594947e08f50
[BLKTAP] Fix SMP debugging assert failures in blktap
blktap is calling non-atomic kernel functions with irqs disabled, which
hits various kernel debug traps if those are enabled. The problem is
req_increase(), which takes the pending_free_lock.
This function is currently only ever called from module initialiation,
where it is impossible for it to race against anything else. Its
companion, req_decrease(), is not called at all.
Fix by removing the offending locking from req_increase() and, while
we're at it, remove req_decrease() entirely.
Signed-off-by: Stephen Tweedie <sct@xxxxxxxxxx>
---
linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c | 37 -----------------------
1 files changed, 1 insertion(+), 36 deletions(-)
diff -r 460f2c954cca -r 5f5e3b4c6fba
linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c
--- a/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c Thu Sep 28 11:52:17
2006 -0700
+++ b/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c Thu Sep 28 12:03:01
2006 -0700
@@ -694,10 +694,7 @@ static int req_increase(void)
{
int i, j;
struct page *page;
- unsigned long flags;
int ret;
-
- spin_lock_irqsave(&pending_free_lock, flags);
ret = -EINVAL;
if (mmap_alloc >= MAX_PENDING_REQS || mmap_lock)
@@ -763,8 +760,7 @@ static int req_increase(void)
mmap_alloc++;
DPRINTK("# MMAPs increased to %d\n",mmap_alloc);
- done:
- spin_unlock_irqrestore(&pending_free_lock, flags);
+done:
return ret;
}
@@ -792,37 +788,6 @@ static void mmap_req_del(int mmap)
mmap_lock = 0;
DPRINTK("# MMAPs decreased to %d\n",mmap_alloc);
mmap_alloc--;
-}
-
-/*N.B. Currently unused - will be accessed via sysfs*/
-static void req_decrease(void)
-{
- pending_req_t *req;
- int i;
- unsigned long flags;
-
- spin_lock_irqsave(&pending_free_lock, flags);
-
- DPRINTK("Req decrease called.\n");
- if (mmap_lock || mmap_alloc == 1)
- goto done;
-
- mmap_lock = 1;
- mmap_inuse = MAX_PENDING_REQS;
-
- /*Go through reqs and remove any that aren't in use*/
- for (i = 0; i < MAX_PENDING_REQS ; i++) {
- req = &pending_reqs[mmap_alloc-1][i];
- if (req->inuse == 0) {
- list_del(&req->free_list);
- mmap_inuse--;
- }
- }
- if (mmap_inuse == 0)
- mmap_req_del(mmap_alloc-1);
- done:
- spin_unlock_irqrestore(&pending_free_lock, flags);
- return;
}
static pending_req_t* alloc_req(void)
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