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Groups > linux.kernel > #1283742

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

From tip-bot for Peter Zijlstra <tipbot@zytor.com>
Newsgroups linux.kernel
Subject [tip:locking/core] sched/wait: Fix signal handling in bit wait helpers
Date 2015-12-04 13:00 +0100
Message-ID <qBXbS-2b5-47@gated-at.bofh.it> (permalink)
References <qASQW-1Dr-23@gated-at.bofh.it>
Organization linux.* mail to news gateway

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Commit-ID:  68985633bccb6066bf1803e316fbc6c1f5b796d6
Gitweb:     http://git.kernel.org/tip/68985633bccb6066bf1803e316fbc6c1f5b796d6
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue, 1 Dec 2015 14:04:04 +0100
Committer:  Ingo Molnar <mingo@kernel.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@arm.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: mark.rutland@arm.com
Cc: neilb@suse.de
Cc: oleg@redhat.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@kernel.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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Thread

Re: [BISECTED] rcu_sched self-detected stall since 3.17 Peter Zijlstra <peterz@infradead.org> - 2015-12-01 14:10 +0100
  Re: [BISECTED] rcu_sched self-detected stall since 3.17 Vladimir Murzin <vladimir.murzin@arm.com> - 2015-12-02 10:10 +0100
  [tip:locking/core] sched/wait:   Fix signal handling in bit wait helpers tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2015-12-04 13:00 +0100
    Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait  helpers Peter Zijlstra <peterz@infradead.org> - 2015-12-08 11:50 +0100
      Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait helpers NeilBrown <nfbrown@novell.com> - 2015-12-09 02:10 +0100
        Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait  helpers Peter Zijlstra <peterz@infradead.org> - 2015-12-09 08:50 +0100
          Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait helpers NeilBrown <nfbrown@novell.com> - 2015-12-09 22:40 +0100
            Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait  helpers Peter Zijlstra <peterz@infradead.org> - 2015-12-10 14:20 +0100
              Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait helpers Paul Turner <pjt@google.com> - 2015-12-11 12:40 +0100
                Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait  helpers Peter Zijlstra <peterz@infradead.org> - 2015-12-11 12:50 +0100
                Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait  helpers Vladimir Murzin <vladimir.murzin@arm.com> - 2015-12-11 13:00 +0100
                Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait  helpers Jan Stancek <jstancek@redhat.com> - 2015-12-11 14:10 +0100
                Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait  helpers Peter Zijlstra <peterz@infradead.org> - 2015-12-11 14:30 +0100
                Re: [tip:locking/core] sched/wait: Fix signal handling in bit wait  helpers Vladimir Murzin <vladimir.murzin@arm.com> - 2015-12-11 19:00 +0100

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