Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 20/32] nohz/cpuset: Restart the tick if printk needs it | Date | Mon, 15 Aug 2011 17:52:17 +0200 |
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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.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Anton Blanchard <anton@au1.ibm.com> Cc: Avi Kivity <avi@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Menage <menage@google.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stephen Hemminger <shemminger@vyatta.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Pepper <lnxninja@linux.vnet.ibm.com> --- kernel/printk.c | 17 ++++++++++++++++- 1 files changed, 16 insertions(+), 1 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c index 3518539..aff07f0 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -41,6 +41,7 @@ #include <linux/cpu.h> #include <linux/notifier.h> #include <linux/rculist.h> +#include <linux/tick.h> #include <asm/uaccess.h> @@ -1220,8 +1221,22 @@ 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_write(printk_pending, 1); + /* 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 the + * printk_pending value and thus keep a periodic tick behaviour. + * Unless it's possible tick_nohz_adaptive_mode() reads its value + * before the barrier() ? + */ + if (tick_nohz_adaptive_mode()) + smp_cpuset_update_nohz(smp_processor_id()); + } } /** -- 1.7.5.4
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