From: Peter Zijlstra Date: Wed, 14 Aug 2013 12:51:00 +0000 (+0200) Subject: sched, x86: Provide a per-cpu preempt_count implementation X-Git-Tag: omap-for-v3.13/fixes-for-merge-window-take2~40^2~111 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c2daa3bed53a81171cf8c1a36db798e82b91afe8;p=pandora-kernel.git sched, x86: Provide a per-cpu preempt_count implementation Convert x86 to use a per-cpu preemption count. The reason for doing so is that accessing per-cpu variables is a lot cheaper than accessing thread_info variables. We still need to save/restore the actual preemption count due to PREEMPT_ACTIVE so we place the per-cpu __preempt_count variable in the same cache-line as the other hot __switch_to() variables such as current_task. NOTE: this save/restore is required even for !PREEMPT kernels as cond_resched() also relies on preempt_count's PREEMPT_ACTIVE to ignore task_struct::state. Also rename thread_info::preempt_count to ensure nobody is 'accidentally' still poking at it. Suggested-by: Linus Torvalds Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-gzn5rfsf8trgjoqx8hyayy3q@git.kernel.org Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed