From mboxrd@z Thu Jan 1 00:00:00 1970 From: srivatsa.bhat@linux.vnet.ibm.com (Srivatsa S. Bhat) Date: Tue, 22 Jan 2013 13:07:19 +0530 Subject: [PATCH v5 16/45] time/clocksource: Use get/put_online_cpus_atomic() to prevent CPU offline In-Reply-To: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> Message-ID: <20130122073713.13822.11706.stgit@srivatsabhat.in.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 Signed-off-by: Srivatsa S. Bhat --- 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 /* for spin_unlock_irq() using preempt_count() m68k */ #include #include +#include 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; }