[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>
diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index 72c434c..1687521 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 @@
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 @@
{
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 @@
{
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 @@
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 @@
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)
