[PATCH v5 16/45] time/clocksource: Use get/put_online_cpus_atomic() to prevent CPU offline
From: Srivatsa S. Bhat <hidden>
Date: 2013-01-22 07:39:30
Also in:
linux-arch, linux-pm, linuxppc-dev, lkml, netdev
Subsystem:
the rest, timekeeping, clocksource core, ntp, alarmtimer · Maintainers:
Linus Torvalds, John Stultz, Thomas Gleixner
Once stop_machine() is gone from the CPU offline path, we won't be able to depend on preempt_disable() or local_irq_disable() to prevent CPUs from going offline from under us. Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, while invoking from atomic context. Cc: John Stultz <redacted> Signed-off-by: Srivatsa S. Bhat <redacted> --- kernel/time/clocksource.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index c958338..1c8d735 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c@@ -30,6 +30,7 @@ #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ #include <linux/tick.h> #include <linux/kthread.h> +#include <linux/cpu.h> void timecounter_init(struct timecounter *tc, const struct cyclecounter *cc,
@@ -320,11 +321,13 @@ static void clocksource_watchdog(unsigned long data) * Cycle through CPUs to check if the CPUs stay synchronized * to each other. */ + get_online_cpus_atomic(); next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); if (next_cpu >= nr_cpu_ids) next_cpu = cpumask_first(cpu_online_mask); watchdog_timer.expires += WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, next_cpu); + put_online_cpus_atomic(); out: spin_unlock(&watchdog_lock); }
@@ -336,7 +339,9 @@ static inline void clocksource_start_watchdog(void) init_timer(&watchdog_timer); watchdog_timer.function = clocksource_watchdog; watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; + get_online_cpus_atomic(); add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask)); + put_online_cpus_atomic(); watchdog_running = 1; }