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[MTD] mtdoops: Ensure sequential write to the buffer

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Add a spinlock to ensure writes to the mtdoops buffer memory are
sequential and don't race.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
This commit is contained in:
Richard Purdie 2008-01-29 10:21:56 +00:00 committed by David Woodhouse
parent 6ce0a856c1
commit 47c152b88c
1 changed files with 28 additions and 0 deletions
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28
drivers/mtd/mtdoops.c
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@ -28,6 +28,7 @@
#include <linux/workqueue.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/spinlock.h>
#include <linux/mtd/mtd.h>
#define OOPS_PAGE_SIZE 4096
@ -42,6 +43,9 @@ struct mtdoops_context {
int nextcount;
void *oops_buf;
/* writecount and disabling ready are spin lock protected */
spinlock_t writecount_lock;
int ready;
int writecount;
} oops_cxt;
@ -290,11 +294,22 @@ static void mtdoops_console_sync(void)
{
struct mtdoops_context *cxt = &oops_cxt;
struct mtd_info *mtd = cxt->mtd;
unsigned long flags;
if (!cxt->ready || !mtd || cxt->writecount == 0)
return;
/*
* Once ready is 0 and we've held the lock no further writes to the
* buffer will happen
*/
spin_lock_irqsave(&cxt->writecount_lock, flags);
if (!cxt->ready) {
spin_unlock_irqrestore(&cxt->writecount_lock, flags);
return;
}
cxt->ready = 0;
spin_unlock_irqrestore(&cxt->writecount_lock, flags);
schedule_work(&cxt->work_write);
}
@ -304,6 +319,7 @@ mtdoops_console_write(struct console *co, const char *s, unsigned int count)
{
struct mtdoops_context *cxt = co->data;
struct mtd_info *mtd = cxt->mtd;
unsigned long flags;
if (!oops_in_progress) {
mtdoops_console_sync();
@ -313,6 +329,13 @@ mtdoops_console_write(struct console *co, const char *s, unsigned int count)
if (!cxt->ready || !mtd)
return;
/* Locking on writecount ensures sequential writes to the buffer */
spin_lock_irqsave(&cxt->writecount_lock, flags);
/* Check ready status didn't change whilst waiting for the lock */
if (!cxt->ready)
return;
if (cxt->writecount == 0) {
u32 *stamp = cxt->oops_buf;
*stamp = cxt->nextcount;
@ -324,6 +347,11 @@ mtdoops_console_write(struct console *co, const char *s, unsigned int count)
memcpy(cxt->oops_buf + cxt->writecount, s, count);
cxt->writecount += count;
spin_unlock_irqrestore(&cxt->writecount_lock, flags);
if (cxt->writecount == OOPS_PAGE_SIZE)
mtdoops_console_sync();
}
static int __init mtdoops_console_setup(struct console *co, char *options)