[tip:sched/core] sched: Exclude cond_resched() from nested sleep test

tip-bot for Peter Zijlstra
2014-10-28T11:13:22Z

Commit-ID: 3427445afd26bd2395f29241319283a93f362cd0
Gitweb: http://git.kernel.org/tip/3427445afd26bd2395f29241319283a93f362cd0
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 24 Sep 2014 10:18:56 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 28 Oct 2014 10:56:57 +0100

sched: Exclude cond_resched() from nested sleep test

cond_resched() is a preemption point, not strictly a blocking
primitive, so exclude it from the ->state test.

In particular, preemption preserves task_struct::state.

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: Alex Elder <alex.elder@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Axel Lin <axel.lin@ingics.com>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20140924082242.656559952@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
include/linux/kernel.h | 3 +++
include/linux/sched.h | 6 +++---
kernel/sched/core.c | 12 +++++++++---
3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 5068a0d..446d76a 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -162,6 +162,7 @@ extern int _cond_resched(void);
#endif

#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
+ void ___might_sleep(const char *file, int line, int preempt_offset);
void __might_sleep(const char *file, int line, int preempt_offset);
/**
* might_sleep - annotation for functions that can sleep
@@ -177,6 +178,8 @@ extern int _cond_resched(void);
do { __might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0)
# define sched_annotate_sleep() __set_current_state(TASK_RUNNING)
#else
+ static inline void ___might_sleep(const char *file, int line,
+ int preempt_offset) { }
static inline void __might_sleep(const char *file, int line,
int preempt_offset) { }
# define might_sleep() do { might_resched(); } while (0)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4648e07..4400ddc 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2806,7 +2806,7 @@ static inline int signal_pending_state(long state, struct task_struct *p)
extern int _cond_resched(void);

#define cond_resched() ({ \
- __might_sleep(__FILE__, __LINE__, 0); \
+ ___might_sleep(__FILE__, __LINE__, 0); \
_cond_resched(); \
})

@@ -2819,14 +2819,14 @@ extern int __cond_resched_lock(spinlock_t *lock);
#endif

#define cond_resched_lock(lock) ({ \
- __might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET); \
+ ___might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);\
__cond_resched_lock(lock); \
})

extern int __cond_resched_softirq(void);

#define cond_resched_softirq() ({ \
- __might_sleep(__FILE__, __LINE__, SOFTIRQ_DISABLE_OFFSET); \
+ ___might_sleep(__FILE__, __LINE__, SOFTIRQ_DISABLE_OFFSET); \
__cond_resched_softirq(); \
})

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5b4b96b..b9f78f1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7296,8 +7296,6 @@ static inline int preempt_count_equals(int preempt_offset)

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,
@@ -7311,6 +7309,14 @@ void __might_sleep(const char *file, int line, int preempt_offset)
(void *)current->task_state_change))
__set_current_state(TASK_RUNNING);

+ ___might_sleep(file, line, preempt_offset);
+}
+EXPORT_SYMBOL(__might_sleep);
+
+void ___might_sleep(const char *file, int line, int preempt_offset)
+{
+ static unsigned long prev_jiffy; /* ratelimiting */
+
rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */
if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
!is_idle_task(current)) ||
@@ -7340,7 +7346,7 @@ void __might_sleep(const char *file, int line, int preempt_offset)
#endif
dump_stack();
}
-EXPORT_SYMBOL(__might_sleep);
+EXPORT_SYMBOL(___might_sleep);
#endif

#ifdef CONFIG_MAGIC_SYSRQ