linux-kernel - Re: [RESEND PATCH v4] drm: Don't free jobs in wait_event

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Date:   Fri, 25 Oct 2019 11:43:27 +0200
From:   Christian Gmeiner <christian.gmeiner@...il.com>
To:     Steven Price <steven.price@....com>
Cc:     Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...ux.ie>,
        Sharat Masetty <smasetty@...eaurora.org>,
        LKML <linux-kernel@...r.kernel.org>,
        DRI mailing list <dri-devel@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        Sam Ravnborg <sam@...nborg.org>,
        Christian König <christian.koenig@....com>,
        Erico Nunes <nunes.erico@...il.com>
Subject: Re: [RESEND PATCH v4] drm: Don't free jobs in wait_event_interruptible()

Am Do., 24. Okt. 2019 um 18:25 Uhr schrieb Steven Price <steven.price@....com>:
>
> drm_sched_cleanup_jobs() attempts to free finished jobs, however because
> it is called as the condition of wait_event_interruptible() it must not
> sleep. Unfortuantly some free callbacks (notibly for Panfrost) do sleep.
>
> Instead let's rename drm_sched_cleanup_jobs() to
> drm_sched_get_cleanup_job() and simply return a job for processing if
> there is one. The caller can then call the free_job() callback outside
> the wait_event_interruptible() where sleeping is possible before
> re-checking and returning to sleep if necessary.
>
> Signed-off-by: Steven Price <steven.price@....com>

Tested-by: Christian Gmeiner <christian.gmeiner@...il.com>

Without this patch I get the following warning:

[  242.935254] ------------[ cut here ]------------
[  242.940044] WARNING: CPU: 2 PID: 109 at kernel/sched/core.c:6731
__might_sleep+0x94/0xa8
[  242.948242] do not call blocking ops when !TASK_RUNNING; state=1
set at [<38751e36>] prepare_to_wait_event+0xa8/0x180
[  242.958923] Modules linked in:
[  242.962010] CPU: 2 PID: 109 Comm: 130000.gpu Not tainted 5.4.0-rc4 #10
[  242.968551] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
[  242.975112] [<c0113160>] (unwind_backtrace) from [<c010cf34>]
(show_stack+0x10/0x14)
[  242.982879] [<c010cf34>] (show_stack) from [<c0c065ec>]
(dump_stack+0xd8/0x110)
[  242.990213] [<c0c065ec>] (dump_stack) from [<c0128adc>] (__warn+0xc0/0x10c)
[  242.997194] [<c0128adc>] (__warn) from [<c0128f10>]
(warn_slowpath_fmt+0x8c/0xb8)
[  243.004697] [<c0128f10>] (warn_slowpath_fmt) from [<c01598bc>]
(__might_sleep+0x94/0xa8)
[  243.012810] [<c01598bc>] (__might_sleep) from [<c0c246e4>]
(__mutex_lock+0x38/0xa1c)
[  243.020571] [<c0c246e4>] (__mutex_lock) from [<c0c250e4>]
(mutex_lock_nested+0x1c/0x24)
[  243.028600] [<c0c250e4>] (mutex_lock_nested) from [<c064f020>]
(etnaviv_cmdbuf_free+0x40/0x8c)
[  243.037233] [<c064f020>] (etnaviv_cmdbuf_free) from [<c06503a0>]
(etnaviv_submit_put+0x38/0x1c8)
[  243.046042] [<c06503a0>] (etnaviv_submit_put) from [<c064177c>]
(drm_sched_cleanup_jobs+0xc8/0xec)
[  243.055021] [<c064177c>] (drm_sched_cleanup_jobs) from [<c06419b4>]
(drm_sched_main+0x214/0x298)
[  243.063826] [<c06419b4>] (drm_sched_main) from [<c0152890>]
(kthread+0x140/0x158)
[  243.071329] [<c0152890>] (kthread) from [<c01010b4>]
(ret_from_fork+0x14/0x20)
[  243.078563] Exception stack(0xec691fb0 to 0xec691ff8)
[  243.083630] 1fa0:                                     00000000
00000000 00000000 00000000
[  243.091822] 1fc0: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000
[  243.100013] 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[  243.106795] irq event stamp: 321
[  243.110098] hardirqs last  enabled at (339): [<c0193854>]
console_unlock+0x430/0x620
[  243.117864] hardirqs last disabled at (346): [<c01934cc>]
console_unlock+0xa8/0x620
[  243.125592] softirqs last  enabled at (362): [<c01024e0>]
__do_softirq+0x2c0/0x590
[  243.133232] softirqs last disabled at (373): [<c0130ed0>]
irq_exit+0x100/0x18c
[  243.140517] ---[ end trace 8afcd79e9e2725b2 ]---

-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info/privacypolicy