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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2008-08-08 21:47:09 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-08-11 13:46:53 +0200 |
| commit | b845b517b5e3706a3729f6ea83b88ab85f0725b0 (patch) | |
| tree | 4311e4c2e6c3fdbdbe89149d1501944294186455 | |
| parent | 796aadeb1b2db9b5d463946766c5bbfd7717158c (diff) | |
| download | linux-b845b517b5e3706a3729f6ea83b88ab85f0725b0.tar.gz linux-b845b517b5e3706a3729f6ea83b88ab85f0725b0.tar.bz2 linux-b845b517b5e3706a3729f6ea83b88ab85f0725b0.zip | |
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>
| -rw-r--r-- | include/linux/kernel.h | 4 | ||||
| -rw-r--r-- | kernel/printk.c | 19 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 2 | ||||
| -rw-r--r-- | kernel/timer.c | 1 |
4 files changed, 23 insertions, 3 deletions
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index aaa998f65c7a..113ac8d0425f 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -200,6 +200,8 @@ extern struct ratelimit_state printk_ratelimit_state; extern int printk_ratelimit(void); extern bool printk_timed_ratelimit(unsigned long *caller_jiffies, unsigned int interval_msec); +extern void printk_tick(void); +extern int printk_needs_cpu(int); #else static inline int vprintk(const char *s, va_list args) __attribute__ ((format (printf, 1, 0))); @@ -211,6 +213,8 @@ static inline int printk_ratelimit(void) { return 0; } static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \ unsigned int interval_msec) \ { return false; } +static inline void printk_tick(void) { } +static inline int printk_needs_cpu(int) { return 0; } #endif extern void asmlinkage __attribute__((format(printf, 1, 2))) diff --git a/kernel/printk.c b/kernel/printk.c index b51b1567bb55..655cc2ca10cc 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 825b4c00fe44..c13d4f182370 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 03bc7f1f1593..510fe69351ca 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); } |