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SubjectRe: bad: scheduling while atomic! (Part Deux)
On Sun, 15 June 2003 16:07:29 +0100, Russell King wrote:
>
> Sigh. Another MTD deadlock, and cause of scheduling badness on UP preempt.
>
> David, I think MTD needs an audit to ensure that no further cases exist.

Could this be done with smatch plus some perl? Being a lazy bastard,
I like the idea of letting the machines do the boring repetetive job.

> static void cfi_intelext_sync (struct mtd_info *mtd)
> {
> for (i=0; !ret && i<cfi->numchips; i++) {
> chip = &cfi->chips[i];
>
> spin_lock(chip->mutex);
> ret = get_chip(map, chip, chip->start, FL_SYNCING);
> ...
> }
>
> /* Unlock the chips again */
>
> for (i--; i >=0; i--) {
> chip = &cfi->chips[i];
>
> spin_lock(chip->mutex);
> ...
> spin_unlock(chip->mutex);
> }
> }

Mindless guess of a fix part 1 & 2 below.

As an anecdote, the stupid copy of cmdset_0001, cmdset_0020, did it
right. Interesting.

Jörn

--
Courage is not the absence of fear, but rather the judgement that
something else is more important than fear.
-- Ambrose Redmoon

--- linux-2.5.71/drivers/mtd/mtd_blkdevs.c~mtd_spinlocks 2003-06-15 16:05:05.000000000 +0200
+++ linux-2.5.71/drivers/mtd/mtd_blkdevs.c 2003-06-15 16:19:43.000000000 +0200
@@ -93,14 +93,13 @@
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);

+ spin_lock_irq(rq->queue_lock);
while (!tr->blkcore_priv->exiting) {
struct request *req;
struct mtd_blktrans_dev *dev;
int res = 0;
DECLARE_WAITQUEUE(wait, current);

- spin_lock_irq(rq->queue_lock);
-
req = elv_next_request(rq);

if (!req) {
@@ -112,6 +111,7 @@
schedule();
remove_wait_queue(&tr->blkcore_priv->thread_wq, &wait);

+ spin_lock_irq(rq->queue_lock);
continue;
}

--- linux-2.5.71/drivers/mtd/chips/cfi_cmdset_0001.c~mtd_spinlocks 2003-06-15 16:05:03.000000000 +0200
+++ linux-2.5.71/drivers/mtd/chips/cfi_cmdset_0001.c 2003-06-15 17:33:43.000000000 +0200
@@ -1423,6 +1423,7 @@
* with the chip now anyway.
*/
}
+ spin_unlock(chip->mutex);
}

/* Unlock the chips again */
-
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