From b845b517b5e3706a3729f6ea83b88ab85f0725b0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 8 Aug 2008 21:47:09 +0200 Subject: printk: robustify printk Avoid deadlocks against rq->lock and xtime_lock by deferring the klogd wakeup by polling from the timer tick. Signed-off-by: Peter Zijlstra Signed-off-by: Ingo Molnar --- kernel/timer.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/timer.c') diff --git a/kernel/timer.c b/kernel/timer.c index 03bc7f1f159..510fe69351c 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -978,6 +978,7 @@ void update_process_times(int user_tick) run_local_timers(); if (rcu_pending(cpu)) rcu_check_callbacks(cpu, user_tick); + printk_tick(); scheduler_tick(); run_posix_cpu_timers(p); } -- cgit v1.2.3 From d82f0b0f6f1a0a25afc288fb7135b1601fe6df18 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 20 Aug 2008 16:46:04 -0700 Subject: migrate_timers: add comment, use spinlock_irq() Add the comment to explain why the double lock in migrate_timers() can't deadlock. Change the code to use spinlock_irq() instead of local_irq_disable() + spin_lock(). Signed-off-by: Oleg Nesterov Acked-by: Steven Rostedt Signed-off-by: Andrew Morton Signed-off-by: Ingo Molnar --- kernel/timer.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) (limited to 'kernel/timer.c') diff --git a/kernel/timer.c b/kernel/timer.c index 03bc7f1f159..e8019cc3418 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -1435,9 +1435,11 @@ static void __cpuinit migrate_timers(int cpu) BUG_ON(cpu_online(cpu)); old_base = per_cpu(tvec_bases, cpu); new_base = get_cpu_var(tvec_bases); - - local_irq_disable(); - spin_lock(&new_base->lock); + /* + * The caller is globally serialized and nobody else + * takes two locks at once, deadlock is not possible. + */ + spin_lock_irq(&new_base->lock); spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING); BUG_ON(old_base->running_timer); @@ -1452,8 +1454,7 @@ static void __cpuinit migrate_timers(int cpu) } spin_unlock(&old_base->lock); - spin_unlock(&new_base->lock); - local_irq_enable(); + spin_unlock_irq(&new_base->lock); put_cpu_var(tvec_bases); } #endif /* CONFIG_HOTPLUG_CPU */ -- cgit v1.2.3