From: Linus Walleij <linus.walleij@linaro.org>
To: Sergei Antonov <saproj@gmail.com>
Cc: linux-mmc@vger.kernel.org, Ulf Hansson <ulf.hansson@linaro.org>
Subject: Re: breaking commit: mmc: moxart-mmc: Use sg_miter for PIO
Date: Tue, 23 Apr 2024 13:32:24 +0200 [thread overview]
Message-ID: <CACRpkdY60cQYOC_-dbs7xgW5OH7oCRO2Y5PEDgiS-9V=4pBj_A@mail.gmail.com> (raw)
In-Reply-To: <CABikg9zHfiTX3gR2qUWRTaeuu1FG4rvc7qhJWEj59ukns_-dDg@mail.gmail.com>
On Tue, Apr 23, 2024 at 1:14 PM Sergei Antonov <saproj@gmail.com> wrote:
> On Mon, 22 Apr 2024 at 20:55, Linus Walleij <linus.walleij@linaro.org> wrote:
> > On Sat, Apr 20, 2024 at 10:38 PM Sergei Antonov <saproj@gmail.com> wrote:
> >
> > > [ 7.018270] BUG: scheduling while atomic: kworker/0:1/9/0x00000002
> > (...)
> > > [ 7.057443] CPU: 0 PID: 9 Comm: kworker/0:1 Not tainted 6.8.0-rc4+ #225
> > > [ 7.064527] Hardware name: Generic DT based system
> > > [ 7.069677] Workqueue: events_freezable mmc_rescan
> > > [ 7.075121] unwind_backtrace from show_stack+0x10/0x14
> > > [ 7.080930] show_stack from dump_stack_lvl+0x34/0x44
> > > [ 7.086576] dump_stack_lvl from __schedule_bug+0x64/0x84
> > > [ 7.092608] __schedule_bug from __schedule+0x58/0x594
> > > [ 7.098320] __schedule from schedule+0x74/0xa8
> > > [ 7.103368] schedule from schedule_timeout+0xd4/0x108
> > > [ 7.109070] schedule_timeout from __wait_for_common+0x94/0x120
> > > [ 7.115547] __wait_for_common from moxart_request+0x278/0x468
> > > [ 7.121980] moxart_request from mmc_start_request+0x94/0xa8
> >
> > moxart_transfer_pio() is called from the interrupt handler and
> > should be properly atomic right, so the flags to sg_miter should
> > be fine.
>
> The stack in my message does not include moxart_irq() or
> moxart_transfer_pio(). It is not an IRQ.
>
> As a result of commit 3ee0e7c3e67cab83ffbbe7707b43df8d41c9fe47
> SG_MITER_ATOMIC is used in the context of moxart_request():
> moxart_request() -> moxart_prepare_data() -> sg_miter_start(,,,SG_MITER_ATOMIC)
> and in the same context down in the code a
> wait_for_completion_interruptible_timeout() is called.
This puzzles me since sg_miter_start() isn't doing anything
that is atomic, such as kmap_atomic(), which is only done in
sg_miter_next(). It doesn't even look at the flags, just assign it
to __flags in struct sg_mapping_iter.
I.e. calling sg_miter_start(,,,SG_MITER_ATOMIC) does not
need to happen in an atomic context.
Yours,
Linus Walleij
next prev parent reply other threads:[~2024-04-23 11:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-20 20:38 breaking commit: mmc: moxart-mmc: Use sg_miter for PIO Sergei Antonov
2024-04-22 17:55 ` Linus Walleij
2024-04-23 11:14 ` Sergei Antonov
2024-04-23 11:32 ` Linus Walleij [this message]
2024-05-23 19:53 ` Linus Walleij
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