linux-kernel - [tip:locking/core] sched/wait: Fix signal handling in bit wait helpers

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Date:	Fri, 4 Dec 2015 03:52:12 -0800
From:	tip-bot for Peter Zijlstra <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, efault@....de, tglx@...utronix.de,
	torvalds@...ux-foundation.org, hpa@...or.com,
	vladimir.murzin@....com
Subject: [tip:locking/core] sched/wait:
  Fix signal handling in bit wait helpers

Commit-ID:  68985633bccb6066bf1803e316fbc6c1f5b796d6
Gitweb:     http://git.kernel.org/tip/68985633bccb6066bf1803e316fbc6c1f5b796d6
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Tue, 1 Dec 2015 14:04:04 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 4 Dec 2015 10:10:15 +0100

sched/wait: Fix signal handling in bit wait helpers

Vladimir reported getting RCU stall warnings and bisected it back to
commit:

  743162013d40 ("sched: Remove proliferation of wait_on_bit() action functions")

That commit inadvertently reversed the calls to schedule() and signal_pending(),
thereby not handling the case where the signal receives while we sleep.

Reported-by: Vladimir Murzin <vladimir.murzin@....com>
Tested-by: Vladimir Murzin <vladimir.murzin@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: mark.rutland@....com
Cc: neilb@...e.de
Cc: oleg@...hat.com
Fixes: 743162013d40 ("sched: Remove proliferation of wait_on_bit() action functions")
Fixes: cbbce8220949 ("SCHED: add some "wait..on_bit...timeout()" interfaces.")
Link: http://lkml.kernel.org/r/20151201130404.GL3816@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/wait.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 052e026..f10bd87 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -583,18 +583,18 @@ EXPORT_SYMBOL(wake_up_atomic_t);
 
 __sched int bit_wait(struct wait_bit_key *word)
 {
-	if (signal_pending_state(current->state, current))
-		return 1;
 	schedule();
+	if (signal_pending(current))
+		return -EINTR;
 	return 0;
 }
 EXPORT_SYMBOL(bit_wait);
 
 __sched int bit_wait_io(struct wait_bit_key *word)
 {
-	if (signal_pending_state(current->state, current))
-		return 1;
 	io_schedule();
+	if (signal_pending(current))
+		return -EINTR;
 	return 0;
 }
 EXPORT_SYMBOL(bit_wait_io);
@@ -602,11 +602,11 @@ EXPORT_SYMBOL(bit_wait_io);
 __sched int bit_wait_timeout(struct wait_bit_key *word)
 {
 	unsigned long now = READ_ONCE(jiffies);
-	if (signal_pending_state(current->state, current))
-		return 1;
 	if (time_after_eq(now, word->timeout))
 		return -EAGAIN;
 	schedule_timeout(word->timeout - now);
+	if (signal_pending(current))
+		return -EINTR;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(bit_wait_timeout);
@@ -614,11 +614,11 @@ EXPORT_SYMBOL_GPL(bit_wait_timeout);
 __sched int bit_wait_io_timeout(struct wait_bit_key *word)
 {
 	unsigned long now = READ_ONCE(jiffies);
-	if (signal_pending_state(current->state, current))
-		return 1;
 	if (time_after_eq(now, word->timeout))
 		return -EAGAIN;
 	io_schedule_timeout(word->timeout - now);
+	if (signal_pending(current))
+		return -EINTR;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
--
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