Re: [kbuild] drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:2376 eb_pin_timeline() warn: inconsistent returns '&tl->mutex'.

From: Matthew Brost
Date: Mon Feb 07 2022 - 13:08:20 EST

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In reply to: Dan Carpenter: "[kbuild] drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:2376 eb_pin_timeline() warn: inconsistent returns '&tl->mutex'."
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On Mon, Feb 07, 2022 at 08:59:48PM +0300, Dan Carpenter wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: dfd42facf1e4ada021b939b4e19c935dcdd55566
> commit: 544460c33821b44c2f0c643121303c3dc3f66ef1 drm/i915: Multi-BB execbuf
> config: i386-randconfig-m021-20220207 (https://download.01.org/0day-ci/archive/20220207/202202072340.xZpz7hAb-lkp@xxxxxxxxx/config )
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
>
> If you fix the issue, kindly add following tag as appropriate

This is fixed by the below patch:
https://patchwork.freedesktop.org/patch/msgid/20220111163929.14017-1-matthew.brost@xxxxxxxxx

Matt

> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>
> New smatch warnings:
> drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:2376 eb_pin_timeline() warn: inconsistent returns '&tl->mutex'.
>
> vim +2376 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
>
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2333 static int eb_pin_timeline(struct i915_execbuffer *eb, struct intel_context *ce,
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2334 bool throttle)
> 8f2a1057d6ec21 drivers/gpu/drm/i915/i915_gem_execbuffer.c Chris Wilson 2019-04-25 2335 {
> e5dadff4b09376 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-15 2336 struct intel_timeline *tl;
> 2bf541ff6d06f4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Maarten Lankhorst 2020-08-19 2337 struct i915_request *rq = NULL;
> 8f2a1057d6ec21 drivers/gpu/drm/i915/i915_gem_execbuffer.c Chris Wilson 2019-04-25 2338
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2339 /*
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2340 * Take a local wakeref for preparing to dispatch the execbuf as
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2341 * we expect to access the hardware fairly frequently in the
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2342 * process, and require the engine to be kept awake between accesses.
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2343 * Upon dispatch, we acquire another prolonged wakeref that we hold
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2344 * until the timeline is idle, which in turn releases the wakeref
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2345 * taken on the engine, and the parent device.
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2346 */
> e5dadff4b09376 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-15 2347 tl = intel_context_timeline_lock(ce);
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2348 if (IS_ERR(tl))
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2349 return PTR_ERR(tl);
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2350
> a4e57f9031ccd5 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-04 2351 intel_context_enter(ce);
> 2bf541ff6d06f4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Maarten Lankhorst 2020-08-19 2352 if (throttle)
> 2bf541ff6d06f4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Maarten Lankhorst 2020-08-19 2353 rq = eb_throttle(eb, ce);
> e5dadff4b09376 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-15 2354 intel_context_timeline_unlock(tl);
> e5dadff4b09376 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Chris Wilson 2019-08-15 2355
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2356 if (rq) {
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2357 bool nonblock = eb->file->filp->f_flags & O_NONBLOCK;
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2358 long timeout = nonblock ? 0 : MAX_SCHEDULE_TIMEOUT;
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2359
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2360 if (i915_request_wait(rq, I915_WAIT_INTERRUPTIBLE,
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2361 timeout) < 0) {
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2362 i915_request_put(rq);
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2363
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2364 tl = intel_context_timeline_lock(ce);
>
> This is mutex_lock_interruptible() so it can fail
>
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2365 intel_context_exit(ce);
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2366 intel_context_timeline_unlock(tl);
>
> Leading to an error pointer dereference. Maybe that's why Smatch is
> complaining? Hard to say. Why are we calling mutex_lock if it's
> O_NONBLOCK code?
>
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2367
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2368 if (nonblock)
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2369 return -EWOULDBLOCK;
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2370 else
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2371 return -EINTR;
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2372 }
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2373 i915_request_put(rq);
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2374 }
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2375
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 @2376 return 0;
> 544460c33821b4 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c Matthew Brost 2021-10-14 2377 }
>
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Next message: Bird, Tim: "RE: [PATCH v2 1/1] Documentation: dev-tools: clarify KTAP specification wording"
Previous message: Wei Liu: "Re: [PATCH 1/1] Drivers: hv: vmbus: Rework use of DMA_BIT_MASK(64)"
In reply to: Dan Carpenter: "[kbuild] drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:2376 eb_pin_timeline() warn: inconsistent returns '&tl->mutex'."
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