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

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Message-ID: <202202072340.xZpz7hAb-lkp@intel.com>
Date:   Mon, 7 Feb 2022 20:59:48 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Matthew Brost <matthew.brost@...el.com>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org,
        John Harrison <John.C.Harrison@...el.com>
Subject: [kbuild] drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c:2376
 eb_pin_timeline() warn: inconsistent returns '&tl->mutex'.

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@intel.com/config )
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

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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