Messages in this thread Patch in this message | | | Date | Fri, 06 Nov 2009 13:56:30 -0800 | From | Greg KH <> | Subject | [27/30] printk: robustify printk |
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2.6.29-stable review patch. If anyone has any objections, please let us know.
------------------ From: Peter Zijlstra <a.p.zijlstra@chello.nl>
commit b845b517b5e3706a3729f6ea83b88ab85f0725b0 upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- include/linux/kernel.h | 4 ++++ kernel/printk.c | 19 +++++++++++++++++-- kernel/time/tick-sched.c | 2 +- kernel/timer.c | 1 + 4 files changed, 23 insertions(+), 3 deletions(-)
--- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -200,6 +200,8 @@ extern struct ratelimit_state printk_rat 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) 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))) --- a/kernel/printk.c +++ b/kernel/printk.c @@ -977,10 +977,25 @@ 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; } /** --- 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); } --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -261,7 +261,7 @@ void tick_nohz_stop_sched_tick(int inidl 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
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