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xen-devel
[Xen-devel] [PATCH v3 2/3] hvc_init(): Enforce one-time initialization.
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To: |
Greg Kroah-Hartman <gregkh@xxxxxxx> |
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Subject: |
[Xen-devel] [PATCH v3 2/3] hvc_init(): Enforce one-time initialization. |
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From: |
Miche Baker-Harvey <miche@xxxxxxxxxx> |
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Date: |
Tue, 08 Nov 2011 13:45:04 -0800 |
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Cc: |
Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, Anton Blanchard <anton@xxxxxxxxx>, Amit Shah <amit.shah@xxxxxxxxxx>, Mike Waychison <mikew@xxxxxxxxxx>, ppc-dev <linuxppc-dev@xxxxxxxxxxxxxxxx>, Eric Northrup <digitaleric@xxxxxxxxxx> |
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Mon, 14 Nov 2011 15:47:07 -0800 |
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StGit/0.15 |
hvc_init() must only be called once, and no thread should continue with
hvc_alloc()
until after initialization is complete. The original code does not enforce
either
of these requirements. A new mutex limits entry to hvc_init() to a single
thread,
and blocks all later comers until it has completed.
This patch fixes multiple crash symptoms.
Signed-off-by: Miche Baker-Harvey <miche@xxxxxxxxxx>
---
drivers/tty/hvc/hvc_console.c | 13 +++++++++++--
1 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index b6b2d18..09a6159 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -29,8 +29,9 @@
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/list.h>
-#include <linux/module.h>
#include <linux/major.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
#include <linux/sysrq.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
@@ -84,6 +85,10 @@ static LIST_HEAD(hvc_structs);
* list traversal.
*/
static DEFINE_SPINLOCK(hvc_structs_lock);
+/*
+ * only one task does allocation at a time.
+ */
+static DEFINE_MUTEX(hvc_ports_mutex);
/*
* This value is used to assign a tty->index value to a hvc_struct based
@@ -825,11 +830,15 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
int i;
/* We wait until a driver actually comes along */
+ mutex_lock(&hvc_ports_mutex);
if (!hvc_driver) {
int err = hvc_init();
- if (err)
+ if (err) {
+ mutex_unlock(&hvc_ports_mutex);
return ERR_PTR(err);
+ }
}
+ mutex_unlock(&hvc_ports_mutex);
hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
GFP_KERNEL);
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