From: Shrikanth Hegde Date: Mon, 23 Mar 2026 19:36:30 +0000 (+0530) Subject: timers: Get this_cpu once while clearing the idle state X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=551e49beb1752387aed09eb2a0ea4c82ed1f3a35;p=thirdparty%2Fkernel%2Flinux.git timers: Get this_cpu once while clearing the idle state Calling smp_processor_id() on: - In CONFIG_DEBUG_PREEMPT=y, if preemption/irq is disabled, then it does not print any warning. - In CONFIG_DEBUG_PREEMPT=n, it doesn't do anything apart from getting __smp_processor_id So with both CONFIG_DEBUG_PREEMPT=y/n, in preemption disabled section it is better to cache the value. It saves a few cycles. Though tiny, repeated adds up. timer_clear_idle() is called with interrupts disabled. So cache the value once. Signed-off-by: Shrikanth Hegde Signed-off-by: Thomas Gleixner Reviewed-by: Mukesh Kumar Chaurasiya (IBM) Link: https://patch.msgid.link/20260323193630.640311-5-sshegde@linux.ibm.com --- diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 7e1e3bde6b8b7..04d928c21aba5 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -2319,6 +2319,7 @@ u64 timer_base_try_to_set_idle(unsigned long basej, u64 basem, bool *idle) */ void timer_clear_idle(void) { + int this_cpu = smp_processor_id(); /* * We do this unlocked. The worst outcome is a remote pinned timer * enqueue sending a pointless IPI, but taking the lock would just @@ -2327,9 +2328,9 @@ void timer_clear_idle(void) * path. Required for BASE_LOCAL only. */ __this_cpu_write(timer_bases[BASE_LOCAL].is_idle, false); - if (tick_nohz_full_cpu(smp_processor_id())) + if (tick_nohz_full_cpu(this_cpu)) __this_cpu_write(timer_bases[BASE_GLOBAL].is_idle, false); - trace_timer_base_idle(false, smp_processor_id()); + trace_timer_base_idle(false, this_cpu); /* Activate without holding the timer_base->lock */ tmigr_cpu_activate();