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authorPeter Zijlstra <peterz@infradead.org>2013-08-14 14:51:00 +0200
committerIngo Molnar <mingo@kernel.org>2013-09-25 14:07:57 +0200
commitc2daa3bed53a81171cf8c1a36db798e82b91afe8 (patch)
treea7a7b1676e3101b986276f9ec0eab0ab5183e1ed /arch/x86/kernel/irq_32.c
parenta233f1120c37724938f7201fe2353b2577adaaf9 (diff)
downloadop-kernel-dev-c2daa3bed53a81171cf8c1a36db798e82b91afe8.zip
op-kernel-dev-c2daa3bed53a81171cf8c1a36db798e82b91afe8.tar.gz
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 <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-gzn5rfsf8trgjoqx8hyayy3q@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/irq_32.c')
-rw-r--r--arch/x86/kernel/irq_32.c4
1 files changed, 0 insertions, 4 deletions
diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index 4186755..3fe0663 100644
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -100,9 +100,6 @@ execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
irqctx->tinfo.task = curctx->tinfo.task;
irqctx->tinfo.previous_esp = current_stack_pointer;
- /* Copy the preempt_count so that the [soft]irq checks work. */
- irqctx->tinfo.preempt_count = curctx->tinfo.preempt_count;
-
if (unlikely(overflow))
call_on_stack(print_stack_overflow, isp);
@@ -131,7 +128,6 @@ void irq_ctx_init(int cpu)
THREAD_SIZE_ORDER));
memset(&irqctx->tinfo, 0, sizeof(struct thread_info));
irqctx->tinfo.cpu = cpu;
- irqctx->tinfo.preempt_count = HARDIRQ_OFFSET;
irqctx->tinfo.addr_limit = MAKE_MM_SEG(0);
per_cpu(hardirq_ctx, cpu) = irqctx;
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