Messages in this thread Patch in this message | | | From | chai wen <> | Subject | [PATCH 2/2] softlockup: make detector be aware of task switch of processes hogging cpu | Date | Mon, 4 Aug 2014 15:36:19 +0800 |
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For now, soft lockup detector warns once for each case of process softlockup. But the thread 'watchdog/n' may can not always get cpu at the time slot between the task switch of two processes hogging that cpu. This case is a false negative of "warn only once for a process", as there may be a different process that is going to hog the cpu. Is is better for detector to be aware of it.
Signed-off-by: chai wen <chaiw.fnst@cn.fujitsu.com> --- kernel/watchdog.c | 18 ++++++++++++++++-- 1 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 4c2e11c..908050c 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -42,6 +42,7 @@ static DEFINE_PER_CPU(bool, softlockup_touch_sync); static DEFINE_PER_CPU(bool, soft_watchdog_warn); static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); +static DEFINE_PER_CPU(pid_t, softlockup_warn_pid_saved); #ifdef CONFIG_HARDLOCKUP_DETECTOR static DEFINE_PER_CPU(bool, hard_watchdog_warn); static DEFINE_PER_CPU(bool, watchdog_nmi_touch); @@ -317,6 +318,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) */ duration = is_softlockup(touch_ts); if (unlikely(duration)) { + pid_t pid = task_pid_nr(current); + /* * If a virtual machine is stopped by the host it can look to * the watchdog like a soft lockup, check to see if the host @@ -326,8 +329,18 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) return HRTIMER_RESTART; /* only warn once */ - if (__this_cpu_read(soft_watchdog_warn) == true) + if (__this_cpu_read(soft_watchdog_warn) == true) { + /* + * soft lockup detector should be aware of that there + * may be a task-swicth of two different processes + * hogging the cpu continously + */ + if (__this_cpu_read(softlockup_warn_pid_saved) != pid) { + __this_cpu_write(soft_watchdog_warn, false); + __touch_watchdog(); + } return HRTIMER_RESTART; + } if (softlockup_all_cpu_backtrace) { /* Prevent multiple soft-lockup reports if one cpu is already @@ -342,7 +355,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) printk(KERN_EMERG "BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", smp_processor_id(), duration, - current->comm, task_pid_nr(current)); + current->comm, pid); + __this_cpu_write(softlockup_warn_pid_saved, pid); print_modules(); print_irqtrace_events(current); if (regs) -- 1.7.1
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