From: Dan Carpenter <dan.carpenter@oracle.com>
To: kbuild@lists.01.org
Subject: [peterz-queue:sched/core-sched 10/11] kernel/sched/core.c:5262 pick_next_task() error: we previously assumed 'next' could be null (see line 5258)
Date: Mon, 11 Jan 2021 13:41:37 +0300 [thread overview]
Message-ID: <20210111104137.GC5083@kadam> (raw)
[-- Attachment #1: Type: text/plain, Size: 5105 bytes --]
tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core-sched
head: ead81f232b5b31ab6240a719ff3bad564c3f0e4c
commit: 6f7eefbb382e8c5fa56180f8cd5becb5f882a3d6 [10/11] sched/fair: Snapshot the min_vruntime of CPUs on force idle
config: x86_64-randconfig-m001-20210108 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
smatch warnings:
kernel/sched/core.c:5262 pick_next_task() error: we previously assumed 'next' could be null (see line 5258)
vim +/next +5262 kernel/sched/core.c
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5225
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5226 put_prev_task_balance(rq, prev, rf);
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5227
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5228 smt_mask = cpu_smt_mask(cpu);
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5229) need_sync = !!rq->core->core_cookie;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5230)
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5231) /* reset state */
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5232) rq->core->core_cookie = 0UL;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5233) if (rq->core->core_forceidle) {
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5234) need_sync = true;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5235) fi_before = true;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5236) rq->core->core_forceidle = false;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5237) }
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5238
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5239 /*
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5240 * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5241 *
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5242 * @task_seq guards the task state ({en,de}queues)
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5243 * @pick_seq is the @task_seq we did a selection on
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5244 * @sched_seq is the @pick_seq we scheduled
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5245 *
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5246 * However, preemptions can cause multiple picks on the same task set.
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5247 * 'Fix' this by also increasing @task_seq for every pick.
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5248 */
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5249 rq->core->core_task_seq++;
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5250
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5251) /*
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5252) * Optimize for common case where this CPU has no cookies
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5253) * and there are no cookied tasks running on siblings.
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5254) */
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5255) if (!need_sync) {
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5256) for_each_class(class) {
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5257) next = class->pick_task(rq);
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 @5258) if (next)
^^^^
Will we always find a valid "next"?
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5259) break;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5260) }
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5261)
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 @5262) if (!next->core_cookie) {
^^^^^^^^^^^^^^^^^
Unchecked dereference.
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5263) rq->core_pick = NULL;
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5264) /*
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5265) * For robustness, update the min_vruntime_fi for
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5266) * unconstrained picks as well.
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5267) */
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5268) WARN_ON_ONCE(fi_before);
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5269) task_vruntime_update(rq, next, false);
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5270) goto done;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5271) }
651b592b4b80bae Vineeth Pillai 2020-11-17 5272 }
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5273)
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
[-- Attachment #2: config.gz --]
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WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: kbuild-all@lists.01.org
Subject: [peterz-queue:sched/core-sched 10/11] kernel/sched/core.c:5262 pick_next_task() error: we previously assumed 'next' could be null (see line 5258)
Date: Mon, 11 Jan 2021 13:41:37 +0300 [thread overview]
Message-ID: <20210111104137.GC5083@kadam> (raw)
[-- Attachment #1: Type: text/plain, Size: 5105 bytes --]
tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core-sched
head: ead81f232b5b31ab6240a719ff3bad564c3f0e4c
commit: 6f7eefbb382e8c5fa56180f8cd5becb5f882a3d6 [10/11] sched/fair: Snapshot the min_vruntime of CPUs on force idle
config: x86_64-randconfig-m001-20210108 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
smatch warnings:
kernel/sched/core.c:5262 pick_next_task() error: we previously assumed 'next' could be null (see line 5258)
vim +/next +5262 kernel/sched/core.c
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5225
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5226 put_prev_task_balance(rq, prev, rf);
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5227
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5228 smt_mask = cpu_smt_mask(cpu);
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5229) need_sync = !!rq->core->core_cookie;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5230)
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5231) /* reset state */
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5232) rq->core->core_cookie = 0UL;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5233) if (rq->core->core_forceidle) {
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5234) need_sync = true;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5235) fi_before = true;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5236) rq->core->core_forceidle = false;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5237) }
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5238
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5239 /*
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5240 * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5241 *
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5242 * @task_seq guards the task state ({en,de}queues)
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5243 * @pick_seq is the @task_seq we did a selection on
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5244 * @sched_seq is the @pick_seq we scheduled
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5245 *
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5246 * However, preemptions can cause multiple picks on the same task set.
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5247 * 'Fix' this by also increasing @task_seq for every pick.
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5248 */
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5249 rq->core->core_task_seq++;
2d8ac06b6ca3a0f Peter Zijlstra 2020-11-17 5250
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5251) /*
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5252) * Optimize for common case where this CPU has no cookies
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5253) * and there are no cookied tasks running on siblings.
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5254) */
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5255) if (!need_sync) {
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5256) for_each_class(class) {
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5257) next = class->pick_task(rq);
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 @5258) if (next)
^^^^
Will we always find a valid "next"?
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5259) break;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5260) }
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5261)
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 @5262) if (!next->core_cookie) {
^^^^^^^^^^^^^^^^^
Unchecked dereference.
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5263) rq->core_pick = NULL;
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5264) /*
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5265) * For robustness, update the min_vruntime_fi for
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5266) * unconstrained picks as well.
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5267) */
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5268) WARN_ON_ONCE(fi_before);
6f7eefbb382e8c5 Joel Fernandes (Google 2020-11-17 5269) task_vruntime_update(rq, next, false);
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5270) goto done;
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5271) }
651b592b4b80bae Vineeth Pillai 2020-11-17 5272 }
d7bbf5f9ab91135 Joel Fernandes (Google 2020-11-17 5273)
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
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next reply other threads:[~2021-01-11 10:41 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 10:41 Dan Carpenter [this message]
2021-01-11 10:41 ` [peterz-queue:sched/core-sched 10/11] kernel/sched/core.c:5262 pick_next_task() error: we previously assumed 'next' could be null (see line 5258) Dan Carpenter
-- strict thread matches above, loose matches on Subject: below --
2021-01-08 14:32 kernel test robot
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