From 8eb23b9f35aae413140d3fda766a98092c21e9b0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 24 Sep 2014 10:18:55 +0200 Subject: [PATCH] sched: Debug nested sleeps 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) Cc: tglx@linutronix.de Cc: ilya.dryomov@inktank.com Cc: umgwanakikbuti@gmail.com Cc: oleg@redhat.com Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20140924082242.591637616@infradead.org Signed-off-by: Ingo Molnar --- include/linux/sched.h | 46 +++++++++++++++++++++++++++++++++++++++++-- kernel/sched/core.c | 13 ++++++++++++ 2 files changed, 57 insertions(+), 2 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 320a9779f1b4..4648e07f7d6f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -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) \ @@ -259,11 +296,13 @@ extern char ___assert_task_state[1 - 2*!!( * * If the caller does not need such serialisation then use __set_current_state() */ -#define __set_current_state(state_value) \ +#define __set_current_state(state_value) \ do { current->state = (state_value); } while (0) -#define set_current_state(state_value) \ +#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. */ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0456a55fc27f..5b4b96b27cd7 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -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)) || -- 2.20.1