From d3ed782458f315c30ea679b919a2cc59f2b82565 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 8 May 2007 00:30:03 -0700 Subject: highres/dyntick: prevent xtime lock contention While the !highres/!dyntick code assigns the duty of the do_timer() call to one specific CPU, this was dropped in the highres/dyntick part during development. Steven Rostedt discovered the xtime lock contention on highres/dyntick due to several CPUs trying to update jiffies. Add the single CPU assignement back. In the dyntick case this needs to be handled carefully, as the CPU which has the do_timer() duty must drop the assignement and let it be grabbed by another CPU, which is active. Otherwise the do_timer() calls would not happen during the long sleep. Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Cc: Steven Rostedt Acked-by: Mark Lord Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/time/tick-common.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'kernel/time/tick-common.c') diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index bfda3f7f071..a96ec9ab345 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -31,7 +31,7 @@ DEFINE_PER_CPU(struct tick_device, tick_cpu_device); */ ktime_t tick_next_period; ktime_t tick_period; -static int tick_do_timer_cpu = -1; +int tick_do_timer_cpu __read_mostly = -1; DEFINE_SPINLOCK(tick_device_lock); /* @@ -295,6 +295,12 @@ static void tick_shutdown(unsigned int *cpup) clockevents_exchange_device(dev, NULL); td->evtdev = NULL; } + /* Transfer the do_timer job away from this cpu */ + if (*cpup == tick_do_timer_cpu) { + int cpu = first_cpu(cpu_online_map); + + tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : -1; + } spin_unlock_irqrestore(&tick_device_lock, flags); } -- cgit v1.2.3-70-g09d2