Re: [PATCH] Race condition in del_timer_sync (2.5)

[Linus Torvalds]

On Tue, 2 Sep 2003, Tejun Huh wrote:
> 
>  I'll submit the patch to Linus soon.

I actually already committed it to my tree, since everybody seems to agree 
on it...

		Linus

----
# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#	           ChangeSet	1.1412  -> 1.1413 
#	      kernel/timer.c	1.66    -> 1.67   
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/09/02	torvalds@xxxxxxxxxxxxx	1.1413
# Fix del_timer_sync() SMP memory ordering (from Tejun Huh <tejun@xxxxxxxxxxxxx>)
# 
# From Tejun's posting:
# >
# > This patch fixes a race between del_timer_sync and recursive timers.
# > Current implementation allows the value of timer->base that is used
# > for timer_pending test to be fetched before finishing running_timer
# > test, so it's possible for a recursive time to be pending after
# > del_timer_sync.  Adding smp_rmb before timer_pending removes the race.
# --------------------------------------------
#
diff -Nru a/kernel/timer.c b/kernel/timer.c
--- a/kernel/timer.c	Tue Sep  2 00:55:15 2003
+++ b/kernel/timer.c	Tue Sep  2 00:55:15 2003
@@ -338,6 +338,7 @@
 			break;
 		}
 	}
+	smp_rmb();
 	if (timer_pending(timer))
 		goto del_again;
 

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