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Commit 47c152b8 authored by Richard Purdie's avatar Richard Purdie Committed by David Woodhouse
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[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: default avatarRichard Purdie <rpurdie@rpsys.net>
Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
parent 6ce0a856

drivers/mtd/mtdoops.c

+28 −0
Original line number Diff line number Diff line
@@ -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)