This is a note to let you know that I've just added the patch titled
perf: Fix ring_buffer_attach() RCU sync, again
to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-fix-ring_buffer_attach-rcu-sync-again.patch
and it can be found in the queue-4.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 2f993cf093643b98477c421fa2b9a98dcc940323 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <[email protected]>
Date: Sat, 30 May 2015 22:04:25 +0200
Subject: perf: Fix ring_buffer_attach() RCU sync, again
From: Oleg Nesterov <[email protected]>
commit 2f993cf093643b98477c421fa2b9a98dcc940323 upstream.
While looking for other users of get_state/cond_sync. I Found
ring_buffer_attach() and it looks obviously buggy?
Don't we need to ensure that we have "synchronize" _between_
list_del() and list_add() ?
IOW. Suppose that ring_buffer_attach() preempts right_after
get_state_synchronize_rcu() and gp completes before spin_lock().
In this case cond_synchronize_rcu() does nothing and we reuse
->rb_entry without waiting for gp in between?
It also moves the ->rcu_pending check under "if (rb)", to make it
more readable imo.
Signed-off-by: Oleg Nesterov <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Fixes: b69cf53640da ("perf: Fix a race between ring_buffer_detach() and
ring_buffer_attach()")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/events/core.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4331,20 +4331,20 @@ static void ring_buffer_attach(struct pe
WARN_ON_ONCE(event->rcu_pending);
old_rb = event->rb;
- event->rcu_batches = get_state_synchronize_rcu();
- event->rcu_pending = 1;
-
spin_lock_irqsave(&old_rb->event_lock, flags);
list_del_rcu(&event->rb_entry);
spin_unlock_irqrestore(&old_rb->event_lock, flags);
- }
- if (event->rcu_pending && rb) {
- cond_synchronize_rcu(event->rcu_batches);
- event->rcu_pending = 0;
+ event->rcu_batches = get_state_synchronize_rcu();
+ event->rcu_pending = 1;
}
if (rb) {
+ if (event->rcu_pending) {
+ cond_synchronize_rcu(event->rcu_batches);
+ event->rcu_pending = 0;
+ }
+
spin_lock_irqsave(&rb->event_lock, flags);
list_add_rcu(&event->rb_entry, &rb->event_list);
spin_unlock_irqrestore(&rb->event_lock, flags);
Patches currently in stable-queue which might be from [email protected] are
queue-4.1/perf-x86-add-more-broadwell-model-numbers.patch
queue-4.1/perf-x86-intel-bts-fix-ds-area-sharing-with-x86_pmu-events.patch
queue-4.1/perf-fix-ring_buffer_attach-rcu-sync-again.patch
queue-4.1/perf-x86-honor-the-architectural-performance-monitoring-version.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
