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| author | Peter Zijlstra <peterz@infradead.org> | 2015-08-13 23:09:29 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-09-18 09:17:50 +0200 |
| commit | de9b8f5dcbd94bfb1d249907a635f1fb1968e19c (patch) | |
| tree | 82744e9ef61c2cd985c7f9af1f6af287255464ac /kernel | |
| parent | a7d5c189719846889c029c34e24e166a465368fa (diff) | |
| download | linux-de9b8f5dcbd94bfb1d249907a635f1fb1968e19c.tar.bz2 | |
sched: Fix crash trying to dequeue/enqueue the idle thread
Sasha reports that his virtual machine tries to schedule the idle
thread since commit 6c37067e2786 ("sched: Change the
sched_class::set_cpus_allowed() calling context").
Hit trace shows this happening from idle_thread_get()->init_idle(),
which is the _second_ init_idle() invocation on that task_struct, the
first being done through idle_init()->fork_idle(). (this code is
insane...)
Because we call init_idle() twice in a row, its ->sched_class ==
&idle_sched_class and ->on_rq = TASK_ON_RQ_QUEUED. This means
do_set_cpus_allowed() think we're queued and will call dequeue_task(),
which is implemented with BUG() for the idle class, seeing how
dequeueing the idle task is a daft thing.
Aside of the whole insanity of calling init_idle() _twice_, change the
code to call set_cpus_allowed_common() instead as this is 'obviously'
before the idle task gets ran etc..
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 6c37067e2786 ("sched: Change the sched_class::set_cpus_allowed() calling context")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/core.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 97d276ff1edb..f0d043ec0182 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4927,7 +4927,15 @@ void init_idle(struct task_struct *idle, int cpu) idle->state = TASK_RUNNING; idle->se.exec_start = sched_clock(); - do_set_cpus_allowed(idle, cpumask_of(cpu)); +#ifdef CONFIG_SMP + /* + * Its possible that init_idle() gets called multiple times on a task, + * in that case do_set_cpus_allowed() will not do the right thing. + * + * And since this is boot we can forgo the serialization. + */ + set_cpus_allowed_common(idle, cpumask_of(cpu)); +#endif /* * We're having a chicken and egg problem, even though we are * holding rq->lock, the cpu isn't yet set to this cpu so the @@ -4944,7 +4952,7 @@ void init_idle(struct task_struct *idle, int cpu) rq->curr = rq->idle = idle; idle->on_rq = TASK_ON_RQ_QUEUED; -#if defined(CONFIG_SMP) +#ifdef CONFIG_SMP idle->on_cpu = 1; #endif raw_spin_unlock(&rq->lock); @@ -4959,7 +4967,7 @@ void init_idle(struct task_struct *idle, int cpu) idle->sched_class = &idle_sched_class; ftrace_graph_init_idle_task(idle, cpu); vtime_init_idle(idle, cpu); -#if defined(CONFIG_SMP) +#ifdef CONFIG_SMP sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu); #endif } |