The patch titled
rcu: fix rcutree grace-period-latency bug on small systems
has been added to the -mm tree. Its filename is
rcu-fix-rcutree-grace-period-latency-bug-on-small-systems.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: rcu: fix rcutree grace-period-latency bug on small systems
From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Kudos to Andi Kleen for finding a grace-period-latency problem! The
problem was that the special-case code for small machines never updated
the ->signaled field to indicate that grace-period initialization had
completed, which prevented force_quiescent_state() from ever expediting
grace periods. This problem resulted in grace periods extending for more
than 20 seconds. Not subtle. I introduced this bug during my inspection
process when I fixed a race between grace-period initialization and
force_quiescent_state() execution.
The following patch properly updates the ->signaled field for the
"small"-system case (no more than 32 CPUs for 32-bit kernels and no more
than 64 CPUs for 64-bit kernels).
I believe that this patch should be included for 2.6.29.
Reported-by: Andi Kleen <andi@xxxxxxxxxxxxxx>
Tested-by: Andi Kleen <andi@xxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/rcutree.c | 1 +
1 file changed, 1 insertion(+)
diff -puN kernel/rcutree.c~rcu-fix-rcutree-grace-period-latency-bug-on-small-systems kernel/rcutree.c
--- a/kernel/rcutree.c~rcu-fix-rcutree-grace-period-latency-bug-on-small-systems
+++ a/kernel/rcutree.c
@@ -572,6 +572,7 @@ rcu_start_gp(struct rcu_state *rsp, unsi
/* Special-case the common single-level case. */
if (NUM_RCU_NODES == 1) {
rnp->qsmask = rnp->qsmaskinit;
+ rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
_
Patches currently in -mm which might be from paulmck@xxxxxxxxxxxxxxxxxx are
origin.patch
linux-next.patch
rcu-fix-rcutree-grace-period-latency-bug-on-small-systems.patch
kmemleak-add-the-base-support.patch
kmemleak-add-the-base-support-fix.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
