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authorWang Qing <wangqing@vivo.com>2021-03-24 19:40:29 +0800
committerTejun Heo <tj@kernel.org>2021-04-04 13:26:49 -0400
commit89e28ce60cb65971c73359c66d076aa20a395cd5 (patch)
treef6185526512cce4a8eb5903926739b51715524a8 /kernel/sysctl.c
parent0687c66b5f666b5ad433f4e94251590d9bc9d10e (diff)
workqueue/watchdog: Make unbound workqueues aware of touch_softlockup_watchdog()
84;0;0c84;0;0c There are two workqueue-specific watchdog timestamps: + @wq_watchdog_touched_cpu (per-CPU) updated by touch_softlockup_watchdog() + @wq_watchdog_touched (global) updated by touch_all_softlockup_watchdogs() watchdog_timer_fn() checks only the global @wq_watchdog_touched for unbound workqueues. As a result, unbound workqueues are not aware of touch_softlockup_watchdog(). The watchdog might report a stall even when the unbound workqueues are blocked by a known slow code. Solution: touch_softlockup_watchdog() must touch also the global @wq_watchdog_touched timestamp. The global timestamp can no longer be used for bound workqueues because it is now updated from all CPUs. Instead, bound workqueues have to check only @wq_watchdog_touched_cpu and these timestamps have to be updated for all CPUs in touch_all_softlockup_watchdogs(). Beware: The change might cause the opposite problem. An unbound workqueue might get blocked on CPU A because of a real softlockup. The workqueue watchdog would miss it when the timestamp got touched on CPU B. It is acceptable because softlockups are detected by softlockup watchdog. The workqueue watchdog is there to detect stalls where a work never finishes, for example, because of dependencies of works queued into the same workqueue. V3: - Modify the commit message clearly according to Petr's suggestion. Signed-off-by: Wang Qing <wangqing@vivo.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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