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sched: Debug nested sleeps

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Validate we call might_sleep() with TASK_RUNNING, which catches places
where we nest blocking primitives, eg. mutex usage in a wait loop.

Since all blocking is arranged through task_struct::state, nesting
this will cause the inner primitive to set TASK_RUNNING and the outer
will thus not block.

Another observed problem is calling a blocking function from
schedule()->sched_submit_work()->blk_schedule_flush_plug() which will
then destroy the task state for the actual __schedule() call that
comes after it.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: oleg@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140924082242.591637616@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-09-24 10:18:55 +02:00 committed by Ingo Molnar
parent 26cabd3125
commit 8eb23b9f35
2 changed files with 57 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

42
include/linux/sched.h
View file

@ -243,6 +243,43 @@ extern char ___assert_task_state[1 - 2*!!(
((task->state & TASK_UNINTERRUPTIBLE) != 0 && \
(task->flags & PF_FROZEN) == 0)
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
#define __set_task_state(tsk, state_value) \
do { \
(tsk)->task_state_change = _THIS_IP_; \
(tsk)->state = (state_value); \
} while (0)
#define set_task_state(tsk, state_value) \
do { \
(tsk)->task_state_change = _THIS_IP_; \
set_mb((tsk)->state, (state_value)); \
} while (0)
/*
* set_current_state() includes a barrier so that the write of current->state
* is correctly serialised wrt the caller's subsequent test of whether to
* actually sleep:
*
* set_current_state(TASK_UNINTERRUPTIBLE);
* if (do_i_need_to_sleep())
* schedule();
*
* If the caller does not need such serialisation then use __set_current_state()
*/
#define __set_current_state(state_value) \
do { \
current->task_state_change = _THIS_IP_; \
current->state = (state_value); \
} while (0)
#define set_current_state(state_value) \
do { \
current->task_state_change = _THIS_IP_; \
set_mb(current->state, (state_value)); \
} while (0)
#else
#define __set_task_state(tsk, state_value) \
do { (tsk)->state = (state_value); } while (0)
#define set_task_state(tsk, state_value) \
@ -264,6 +301,8 @@ extern char ___assert_task_state[1 - 2*!!(
#define set_current_state(state_value) \
set_mb(current->state, (state_value))
#endif
/* Task command name length */
#define TASK_COMM_LEN 16
@ -1661,6 +1700,9 @@ struct task_struct {
unsigned int sequential_io;
unsigned int sequential_io_avg;
#endif
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
unsigned long task_state_change;
#endif
};
/* Future-safe accessor for struct task_struct's cpus_allowed. */

13
kernel/sched/core.c
View file

@ -7298,6 +7298,19 @@ void __might_sleep(const char *file, int line, int preempt_offset)
{
static unsigned long prev_jiffy; /* ratelimiting */
/*
* Blocking primitives will set (and therefore destroy) current->state,
* since we will exit with TASK_RUNNING make sure we enter with it,
* otherwise we will destroy state.
*/
if (WARN(current->state != TASK_RUNNING,
"do not call blocking ops when !TASK_RUNNING; "
"state=%lx set at [<%p>] %pS\n",
current->state,
(void *)current->task_state_change,
(void *)current->task_state_change))
__set_current_state(TASK_RUNNING);
rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */
if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
!is_idle_task(current)) ||