From 8b0b1db0133e4218a9b45c09e53793c039edebe1 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 16 Jun 2009 15:33:39 -0700 Subject: remove put_cpu_no_resched() put_cpu_no_resched() is an optimization of put_cpu() which unfortunately can cause high latencies. The nfs iostats code uses put_cpu_no_resched() in a code sequence where a reschedule request caused by an interrupt between the get_cpu() and the put_cpu_no_resched() can delay the reschedule for at least HZ. The other users of put_cpu_no_resched() optimize correctly in interrupt code, but there is no real harm in using the put_cpu() function which is an alias for preempt_enable(). The extra check of the preemmpt count is not as critical as the potential source of missing a reschedule. Debugged in the preempt-rt tree and verified in mainline. Impact: remove a high latency source [akpm@linux-foundation.org: build fix] Signed-off-by: Thomas Gleixner Acked-by: Ingo Molnar Cc: Tony Luck Cc: Trond Myklebust Cc: "J. Bruce Fields" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/ia64/kernel/perfmon.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/ia64') diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c index 8a06dc48059..bdc176cb5e8 100644 --- a/arch/ia64/kernel/perfmon.c +++ b/arch/ia64/kernel/perfmon.c @@ -5595,7 +5595,7 @@ pfm_interrupt_handler(int irq, void *arg) (*pfm_alt_intr_handler->handler)(irq, arg, regs); } - put_cpu_no_resched(); + put_cpu(); return IRQ_HANDLED; } -- cgit v1.2.3