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| author | Richard Purdie <rpurdie@rpsys.net> | 2008-01-29 10:21:56 +0000 |
|---|---|---|
| committer | David Woodhouse <dwmw2@infradead.org> | 2008-02-03 18:18:58 +1100 |
| commit | 47c152b88c185c7e97462a35893df6e552075a8c (patch) | |
| tree | 406c19685ebb030af09384bf2b59559a52810c0b | |
| parent | 6ce0a856c10c8ab8568764436864616efa88e908 (diff) | |
| download | blackbird-op-linux-47c152b88c185c7e97462a35893df6e552075a8c.tar.gz blackbird-op-linux-47c152b88c185c7e97462a35893df6e552075a8c.zip | |
[MTD] mtdoops: Ensure sequential write to the buffer
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>
| -rw-r--r-- | drivers/mtd/mtdoops.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c index 72c434c61b0a..1687521b4aa4 100644 --- a/drivers/mtd/mtdoops.c +++ b/drivers/mtd/mtdoops.c @@ -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) |
