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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Chris Wilson <chris@chris-wilson.co.uk>
Cc:     Jia-Ju Bai <baijiaju1990@gmail.com>, lenb@kernel.org,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] acpi: osl: Replace GFP_ATOMIC with GFP_KERNEL in acpi_os_execute
Date:   Thu, 08 Feb 2018 11:20:39 +0100
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On Thursday, February 8, 2018 11:13:10 AM CET Chris Wilson wrote:
> Quoting Rafael J. Wysocki (2018-02-08 09:51:41)
> > On Thursday, January 25, 2018 11:13:41 AM CET Jia-Ju Bai wrote:
> > > After checking all possible call chains to acpi_os_execute here,
> > > my tool finds that acpi_os_execute is never called in atomic context.
> > > And acpi_os_execute calls acpi_debugger_create_thread 
> > > which calls mutex_lock,
> > > thus it proves again that acpi_os_execute can 
> > > call functions which may sleep.
> > > Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL.
> > > 
> > > This is found by a static analysis tool named DCNS written by myself.
> > > 
> > > Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> > > ---
> > >  drivers/acpi/osl.c |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> > > index 3bb46cb..8ee605e 100644
> > > --- a/drivers/acpi/osl.c
> > > +++ b/drivers/acpi/osl.c
> > > @@ -1066,7 +1066,7 @@ acpi_status acpi_os_execute(acpi_execute_type type,
> > >        * having a static work_struct.
> > >        */
> > >  
> > > -     dpc = kzalloc(sizeof(struct acpi_os_dpc), GFP_ATOMIC);
> > > +     dpc = kzalloc(sizeof(struct acpi_os_dpc), GFP_KERNEL);
> > >       if (!dpc)
> > >               return AE_NO_MEMORY;
> > >  
> > > 
> > 
> > Applied, thanks!
> 
> Hmm, not this patch per se, but 
> 
> https://intel-gfx-ci.01.org/tree/next/next-20180207/fi-bxt-dsi/dmesg0.log
> [  111.378236] BUG: sleeping function called from invalid context at mm/slab.h:420
> [  111.378259] in_atomic(): 1, irqs_disabled(): 1, pid: 1701, name: gem_exec_flush
> [  111.378275] INFO: lockdep is turned off.
> [  111.378277] irq event stamp: 0
> [  111.378280] hardirqs last  enabled at (0): [<          (null)>]           (null)
> [  111.378286] hardirqs last disabled at (0): [<00000000a01fa473>] copy_process.part.7+0x2f1/0x1db0
> [  111.378290] softirqs last  enabled at (0): [<00000000a01fa473>] copy_process.part.7+0x2f1/0x1db0
> [  111.378292] softirqs last disabled at (0): [<          (null)>]           (null)
> [  111.378293] Preemption disabled at:
> [  111.378298] [<ffffffffa18f14f6>] __mutex_lock+0x56/0x9b0
> [  111.378311] CPU: 1 PID: 1701 Comm: gem_exec_flush Tainted: G     U  W        4.15.0-next-20180207-g5d1c98967100-next-20180207 #1
> [  111.378313] Hardware name: Intel Corp. Broxton P/Apollolake RVP1A, BIOS APLKRVPA.X64.0150.B11.1608081044 08/08/2016
> [  111.378314] Call Trace:
> [  111.378318]  <IRQ>
> [  111.378323]  dump_stack+0x5f/0x86
> [  111.378328]  ___might_sleep+0x1d9/0x240
> [  111.378334]  ? acpi_os_execute+0x2d/0x130
> [  111.378338]  kmem_cache_alloc_trace+0x1ae/0x2b0
> [  111.378344]  ? acpi_ev_asynch_enable_gpe+0x2d/0x2d
> [  111.378347]  acpi_os_execute+0x2d/0x130
> [  111.378351]  acpi_ev_gpe_dispatch+0xd7/0x120
> [  111.378355]  acpi_ev_gpe_detect+0x156/0x195
> [  111.378362]  acpi_ev_sci_xrupt_handler+0x16/0x28
> [  111.378365]  acpi_irq+0xd/0x30
> [  111.378369]  __handle_irq_event_percpu+0x3c/0x340
> [  111.378374]  handle_irq_event_percpu+0x1b/0x50
> [  111.378378]  handle_irq_event+0x2f/0x50
> [  111.378381]  handle_fasteoi_irq+0x93/0x150
> [  111.378386]  handle_irq+0x11/0x20
> [  111.378390]  do_IRQ+0x5e/0x120
> [  111.378395]  common_interrupt+0xbb/0xbb
> [  111.378397]  </IRQ>
> 
> does tell us that acpi_os_execute() is called in irq context.

Well, right, thanks!

I overlooked this instance, so dropping the patch.

Thanks,
Rafael