-stable review patch. If anyone has any objections, please let us know. --------------------- From: Thomas Gleixner The NOHZ patch contains a check for softirqs pending when a CPU goes idle. The BUG is unrelated to NOHZ, it just was made visible by the NOHZ patch. The BUG showed up mainly on P4 / hyperthreading enabled machines which lead the investigations into the wrong direction in the first place. The real cause is in cond_resched_softirq(): cond_resched_softirq() is enabling softirqs without invoking the softirq daemon when softirqs are pending. This leads to the warning message in the NOHZ idle code: t1 runs softirq disabled code on CPU#0 interrupt happens, softirq is raised, but deferred (softirqs disabled) t1 calls cond_resched_softirq() enables softirqs via _local_bh_enable() calls schedule() t2 runs t1 is migrated to CPU#1 t2 is done and invokes idle() NOHZ detects the pending softirq Fix: change _local_bh_enable() to local_bh_enable() so the softirq daemon is invoked. Thanks to Anant Nitya for debugging this with great patience ! Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Andrew Morton Cc: Anant Nitya Signed-off-by: Chris Wright Signed-off-by: Greg Kroah-Hartman --- kernel/sched.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- linux-2.6.21.4.orig/kernel/sched.c +++ linux-2.6.21.4/kernel/sched.c @@ -4545,9 +4545,7 @@ int __sched cond_resched_softirq(void) BUG_ON(!in_softirq()); if (need_resched() && system_state == SYSTEM_RUNNING) { - raw_local_irq_disable(); - _local_bh_enable(); - raw_local_irq_enable(); + local_bh_enable(); __cond_resched(); local_bh_disable(); return 1; -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/