Messages in this thread | | | Date | Tue, 8 Apr 2008 10:21:34 +0200 | From | "Dmitry Adamushko" <> | Subject | Re: [PATCH] mtd/chips: add missing set_current_state() to cfi_{amdstd,staa}_sync() |
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On 08/04/2008, Andrew Morton <akpm@linux-foundation.org> wrote: > On Thu, 03 Apr 2008 21:38:23 +0200 > Dmitry Adamushko <dmitry.adamushko@gmail.com> wrote: > > > From: Dmitry Adamushko <dmitry.adamushko@gmail.com> > > Subject: [mtd/chips] add missing set_current_state() to cfi_{amdstd,staa}_sync() > > > > cfi_amdstd_sync() and cfi_staa_sync() call schedule() without changing > > task's state appropriately. > > > > In case of e.g. chip->state == FL_ERASING, cfi_*_sync() will be busy-looping > > either redundantly for a fixed interval of time (for SCHED_NORMAL tasks) or > > possibly endlessly (for RT tasks and UP). > > > > Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com> > > > > --- > > > > diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c > > index d072e87..458d477 100644 > > --- a/drivers/mtd/chips/cfi_cmdset_0002.c > > +++ b/drivers/mtd/chips/cfi_cmdset_0002.c > > @@ -1763,6 +1763,7 @@ static void cfi_amdstd_sync (struct mtd_info *mtd) > > > > default: > > /* Not an idle state */ > > + set_current_state(TASK_UNINTERRUPTIBLE); > > add_wait_queue(&chip->wq, &wait); > > > > spin_unlock(chip->mutex); > > diff --git a/drivers/mtd/chips/cfi_cmdset_0020.c b/drivers/mtd/chips/cfi_cmdset_0020.c > > index b344ff8..492e2ab 100644 > > --- a/drivers/mtd/chips/cfi_cmdset_0020.c > > +++ b/drivers/mtd/chips/cfi_cmdset_0020.c > > @@ -1015,6 +1015,7 @@ static void cfi_staa_sync (struct mtd_info *mtd) > > > > default: > > /* Not an idle state */ > > + set_current_state(TASK_UNINTERRUPTIBLE); > > add_wait_queue(&chip->wq, &wait); > > > > spin_unlock_bh(chip->mutex); > > > The change certainly looks correct. Has it been runtime tested?
It has been tested with an oldish 2.6.8.1 where the problem initially occured. It was a RT task that happened to close an mtd fd (and resulting in ->sync() being called) and ran in the middle of the ->erase op... resulting in a "nice" endless loop.
The versions of cfi_{amdstd,staa}_sync() in the mainline look not that much different from the respective versions in 2.6.8.1.
I guess, it went unnoticed for so long time due to :
(1) apps. don't often directly open/close() fd for mtd partitions; (2) a race against ->erase() (or smth else) is rare; (3) if (1) is not true, then an app. is still unlikely to be RT (in which case, a task just loops until its timeslice is gone).
> > Thanks. >
-- Best regards, Dmitry Adamushko
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