From: Frederic Weisbecker If we are in nohz adaptive mode and printk is called, the tick is missing to wake up the logger. We need to restart the tick when that happens. Do this asynchronously by issuing a tick restart self IPI to avoid deadlocking with the current random locking chain. Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Daniel Lezcano Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: Ingo Molnar Cc: Kevin Hilman Cc: Max Krasnyansky Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Steven Rostedt Cc: Sven-Thorsten Dietrich Cc: Thomas Gleixner --- kernel/printk.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/kernel/printk.c b/kernel/printk.c index 2d607f4..bf9048d 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -42,6 +42,7 @@ #include #include #include +#include #include @@ -1977,8 +1978,20 @@ int printk_needs_cpu(int cpu) void wake_up_klogd(void) { - if (waitqueue_active(&log_wait)) + unsigned long flags; + + if (waitqueue_active(&log_wait)) { this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP); + /* Make it visible from any interrupt from now */ + barrier(); + /* + * It's safe to check that even if interrupts are not disabled. + * If we enable nohz adaptive mode concurrently, we'll see the + * printk_pending value and thus keep a periodic tick behaviour. + */ + if (cpuset_adaptive_nohz()) + smp_cpuset_update_nohz(smp_processor_id()); + } } static void console_cont_flush(char *text, size_t size) -- 1.7.10.4 -- 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/