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Message-ID: <1372717451.2385.58.camel@dabdike>
Subject: Re: [PATCH] block: Fix possible sleep in invalid context
From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Sujit Reddy Thumma <sthumma@codeaurora.org>, Aaron Lu <aaron.lu@intel.com>,
        Jens Axboe <axboe@kernel.dk>, linux-pm@vger.kernel.org,
        linux-scsi@vger.kernel.org, stable@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
Date: Mon, 01 Jul 2013 15:24:11 -0700
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References: <1372692515-31969-1-git-send-email-sthumma@codeaurora.org>
	 <20130701151712.f453745bc0c587f449cc3214@linux-foundation.org>
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On Mon, 2013-07-01 at 15:17 -0700, Andrew Morton wrote:
> On Mon,  1 Jul 2013 20:58:35 +0530 Sujit Reddy Thumma <sthumma@codeaurora.org> wrote:
> 
> > When block runtime PM is enabled following warning is seen
> > while resuming the device.
> > 
> > BUG: sleeping function called from invalid context at
> > .../drivers/base/power/runtime.c:923
> > in_atomic(): 1, irqs_disabled(): 128, pid: 12, name: kworker/0:1
> > [<c0014448>] (unwind_backtrace+0x0/0x120) from
> > [<c03120e4>] (__pm_runtime_suspend+0x34/0xa0) from
> > [<c021c33c>] (blk_post_runtime_resume+0x4c/0x5c) from
> > [<c03297cc>] (scsi_runtime_resume+0x90/0xb4) from
> > [<c0310940>] (__rpm_callback+0x30/0x58) from
> > [<c0310980>] (rpm_callback+0x18/0x28) from
> > [<c0311ab0>] (rpm_resume+0x3dc/0x540) from
> > [<c03120a4>] (pm_runtime_work+0x8c/0x98) from
> > [<c007767c>] (process_one_work+0x238/0x3e4) from
> > [<c0077b90>] (worker_thread+0x1ac/0x2ac) from
> > [<c007cfdc>] (kthread+0x88/0x94) from
> > [<c000ece0>] (kernel_thread_exit+0x0/0x8)
> > 
> > Fix this by releasing spin_lock_irq() before calling
> > pm_runtime_autosuspend() in blk_post_runtime_resume().
> > 
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -3159,16 +3159,18 @@ EXPORT_SYMBOL(blk_pre_runtime_resume);
> >   */
> >  void blk_post_runtime_resume(struct request_queue *q, int err)
> >  {
> > -	spin_lock_irq(q->queue_lock);
> >  	if (!err) {
> > +		spin_lock_irq(q->queue_lock);
> >  		q->rpm_status = RPM_ACTIVE;
> >  		__blk_run_queue(q);
> >  		pm_runtime_mark_last_busy(q->dev);
> > +		spin_unlock_irq(q->queue_lock);
> >  		pm_runtime_autosuspend(q->dev);
> >  	} else {
> > +		spin_lock_irq(q->queue_lock);
> >  		q->rpm_status = RPM_SUSPENDED;
> > +		spin_unlock_irq(q->queue_lock);
> >  	}
> > -	spin_unlock_irq(q->queue_lock);
> >  }
> >  EXPORT_SYMBOL(blk_post_runtime_resume);
> >  #endif
> 
> I suppose we can do this cleanly enough:
> 
> --- a/block/blk-core.c~block-fix-possible-sleep-in-invalid-context-fix
> +++ a/block/blk-core.c
> @@ -3159,15 +3159,14 @@ EXPORT_SYMBOL(blk_pre_runtime_resume);
>   */
>  void blk_post_runtime_resume(struct request_queue *q, int err)
>  {
> +	spin_lock_irq(q->queue_lock);
>  	if (!err) {
> -		spin_lock_irq(q->queue_lock);
>  		q->rpm_status = RPM_ACTIVE;
>  		__blk_run_queue(q);
>  		pm_runtime_mark_last_busy(q->dev);
>  		spin_unlock_irq(q->queue_lock);
>  		pm_request_autosuspend(q->dev);
>  	} else {
> -		spin_lock_irq(q->queue_lock);
>  		q->rpm_status = RPM_SUSPENDED;
>  		spin_unlock_irq(q->queue_lock);
>  	}
> _
> 
> 
> I wonder if we actually need locking around that second write to
> q->rpm_status.

Shouldn't: it's an int, which makes it a 32 bit quantity we believe to
have atomic write properties on every platform.

James


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