[PATCH] mtd/chips: add missing set_current_state() to cfi_{amdstd,staa}_sync() - Kernel

This is a discussion on [PATCH] mtd/chips: add missing set_current_state() to cfi_{amdstd,staa}_sync() - Kernel ; From: Dmitry Adamushko 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 ...

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Thread: [PATCH] mtd/chips: add missing set_current_state() to cfi_{amdstd,staa}_sync()

  1. [PATCH] mtd/chips: add missing set_current_state() to cfi_{amdstd,staa}_sync()

    From: Dmitry Adamushko
    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

    ---

    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);


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  2. Re: [PATCH] mtd/chips: add missing set_current_state() to cfi_{amdstd,staa}_sync()

    On Thu, 03 Apr 2008 21:38:23 +0200
    Dmitry Adamushko wrote:

    > From: Dmitry Adamushko
    > 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
    >
    > ---
    >
    > 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?

    Thanks.
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  3. Re: [PATCH] mtd/chips: add missing set_current_state() to cfi_{amdstd,staa}_sync()

    On 08/04/2008, Andrew Morton wrote:
    > On Thu, 03 Apr 2008 21:38:23 +0200
    > Dmitry Adamushko wrote:
    >
    > > From: Dmitry Adamushko
    > > 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
    > >
    > > ---
    > >
    > > 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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