* [PATCH] POSIX timers RCU optimization fix for clock_gettime
@ 2007-02-04 4:15 Paul E. McKenney
0 siblings, 0 replies; only message in thread
From: Paul E. McKenney @ 2007-02-04 4:15 UTC (permalink / raw)
To: linux-kernel; +Cc: oleg, akpm, johnstul, mingo, tglx, zippel
Fixes an exit()/posix_cpu_clock_get() race spotted by Oleg Nesterov.
Solution is to move the p->signal check under the tasklist_lock.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
posix-cpu-timers.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff -urpNa -X dontdiff linux-2.6.20-rc6-clockrcu/kernel/posix-cpu-timers.c linux-2.6.20-rc6-clockrcu-fixes/kernel/posix-cpu-timers.c
--- linux-2.6.20-rc6-clockrcu/kernel/posix-cpu-timers.c 2007-02-01 13:03:57.000000000 -0800
+++ linux-2.6.20-rc6-clockrcu-fixes/kernel/posix-cpu-timers.c 2007-02-03 16:53:41.000000000 -0800
@@ -312,10 +312,13 @@ int posix_cpu_clock_get(const clockid_t
error = cpu_clock_sample(which_clock,
p, &rtn);
}
- } else if (p->tgid == pid && p->signal) {
+ } else {
read_lock(&tasklist_lock);
- error = cpu_clock_sample_group(which_clock,
- p, &rtn);
+ if (p->tgid == pid && p->signal) {
+ error =
+ cpu_clock_sample_group(which_clock,
+ p, &rtn);
+ }
read_unlock(&tasklist_lock);
}
}
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