The patch titled rcu: fix rcutree grace-period-latency bug on small systems has been removed from the -mm tree. Its filename was rcu-fix-rcutree-grace-period-latency-bug-on-small-systems.patch This patch was dropped because it was merged into mainline or a subsystem tree 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 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