From: Thomas Gleixner Date: Sun, 16 Sep 2007 13:36:43 +0000 (+0200) Subject: clockevents: prevent stale tick update on offline cpu X-Git-Tag: v2.6.23-rc7~35 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5e41d0d60a534d2a5dc9772600a58f44c8d12506;p=pandora-kernel.git clockevents: prevent stale tick update on offline cpu Taking a cpu offline removes the cpu from the online mask before the CPU_DEAD notification is done. The clock events layer does the cleanup of the dead CPU from the CPU_DEAD notifier chain. tick_do_timer_cpu is used to avoid xtime lock contention by assigning the task of jiffies xtime updates to one CPU. If a CPU is taken offline, then this assignment becomes stale. This went unnoticed because most of the time the offline CPU went dead before the online CPU reached __cpu_die(), where the CPU_DEAD state is checked. In the case that the offline CPU did not reach the DEAD state before we reach __cpu_die(), the code in there goes to sleep for 100ms. Due to the stale time update assignment, the system is stuck forever. Take the assignment away when a cpu is not longer in the cpu_online_mask. We do this in the last call to tick_nohz_stop_sched_tick() when the offline CPU is on the way to the final play_dead() idle entry. Signed-off-by: Thomas Gleixner --- Reading git-diff-tree failed