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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2008-08-08 21:47:09 +0200
committerIngo Molnar <mingo@elte.hu>2008-08-11 13:46:53 +0200
commitb845b517b5e3706a3729f6ea83b88ab85f0725b0 (patch)
tree4311e4c2e6c3fdbdbe89149d1501944294186455 /kernel
parent796aadeb1b2db9b5d463946766c5bbfd7717158c (diff)
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 <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/printk.c19
-rw-r--r--kernel/time/tick-sched.c2
-rw-r--r--kernel/timer.c1
3 files changed, 19 insertions, 3 deletions
diff --git a/kernel/printk.c b/kernel/printk.c
index b51b1567bb5..655cc2ca10c 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -982,10 +982,25 @@ int is_console_locked(void)
return console_locked;
}
-void wake_up_klogd(void)
+static DEFINE_PER_CPU(int, printk_pending);
+
+void printk_tick(void)
{
- if (!oops_in_progress && waitqueue_active(&log_wait))
+ if (__get_cpu_var(printk_pending)) {
+ __get_cpu_var(printk_pending) = 0;
wake_up_interruptible(&log_wait);
+ }
+}
+
+int printk_needs_cpu(int cpu)
+{
+ return per_cpu(printk_pending, cpu);
+}
+
+void wake_up_klogd(void)
+{
+ if (waitqueue_active(&log_wait))
+ __get_cpu_var(printk_pending) = 1;
}
/**
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 825b4c00fe4..c13d4f18237 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -255,7 +255,7 @@ void tick_nohz_stop_sched_tick(int inidle)
next_jiffies = get_next_timer_interrupt(last_jiffies);
delta_jiffies = next_jiffies - last_jiffies;
- if (rcu_needs_cpu(cpu))
+ if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu))
delta_jiffies = 1;
/*
* Do not stop the tick, if we are only one off
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);
}