From: Peter Zijlstra Date: Mon, 23 Sep 2013 17:04:26 +0000 (+0200) Subject: sched: Prepare for per-cpu preempt_count X-Git-Tag: omap-for-v3.13/fixes-for-merge-window-take2~40^2~112 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a233f1120c37724938f7201fe2353b2577adaaf9;p=pandora-kernel.git sched: Prepare for per-cpu preempt_count When using per-cpu preempt_count variables we need to save/restore the preempt_count on context switch (into per task storage; for instance the old thread_info::preempt_count variable) because of PREEMPT_ACTIVE. However, this means that on fork() the preempt_count value of the last context switch gets copied and if we had a PREEMPT_ACTIVE switch right before cloning a child task the child task will now too have PREEMPT_ACTIVE set and start its life with an extra PREEMPT_ACTIVE count. Therefore we need to make init_task_preempt_count() unconditional; this resets whatever preempt_count we inherited from our parent process. Doing so for !per-cpu implementations is harmless. For !PREEMPT_COUNT kernels we need to be careful not to start life with an increased preempt_count. Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-4k0b7oy1rcdyzochwiixuwi9@git.kernel.org Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed