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H A D | callout.h | diff 234952 Thu May 03 08:48:04 MDT 2012 kib When callout_reset_on() cannot immediately migrate a callout since it is running on other cpu, the CALLOUT_PENDING flag is temporarily cleared. Then, callout_stop() on this, in fact active, callout fails because CALLOUT_PENDING is not set, and callout_stop() returns 0. Now, in sleepq_check_timeout(), the failed callout_stop() causes the sleepq code to execute mi_switch() without even setting the wmesg, since the switch-out is supposed to be transient. In fact, the thread is put off the CPU for full timeout interval, instead of being put on runq immediately. Until timeout fires, the process is unkillable for obvious reasons. Fix this by marking the migrating callouts with CALLOUT_DFRMIGRATION flag. The flag is cleared by callout_stop_safe() when the function detects a migration, besides returning the success. The softclock() rechecks the flag for migrating callout and cancels its execution if the flag was cleared meantime. PR: misc/166340 Reported, debugging traces provided and tested by: Christian Esken <christian.esken trivago com> Reviewed by: avg, jhb MFC after: 1 week |
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