From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Fernandes Subject: why does this irqsoff tracer output show interrupts disabled between irq to softirq transition? Date: Tue, 1 Mar 2016 21:37:59 -0800 Message-ID: <56D67C37.10207@lab126.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit To: Return-path: Received: from smtp-fw-9102.amazon.com ([207.171.184.29]:48833 "EHLO smtp-fw-9102.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750745AbcCBFiQ (ORCPT ); Wed, 2 Mar 2016 00:38:16 -0500 Received: from ex10-hub-7002.ant.amazon.com (pdx1-ws-svc-lb16-vlan3.amazon.com [10.239.138.214]) by email-inbound-relay-64011.pdx4.amazon.com (8.14.7/8.14.7) with ESMTP id u225c8qE018575 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=FAIL) for ; Wed, 2 Mar 2016 05:38:15 GMT Sender: linux-rt-users-owner@vger.kernel.org List-ID: Hi, I am using the irqsoff tracer on a (slightly old) kernel and I am seeing something like this. As you can see, after servicing the hrtimer_interrupt, and calling irq_exit(), a softirq runs. But the softirq (which happens to be run_timer_softirq) is being called with interrupts disabled, - but from my understanding, interrupts are to remain enabled during softirq operation (unless ofcourse a spinlock is shared between a softirq and an irq handler and someone calls spinlock_irq_save). So considering this, does the below makes sense? Thanks for any insight! mmcqd/0-1435 0d.h1 182us : preempt_count_add <-_raw_spin_lock mmcqd/0-1435 0d.h2 182us : enqueue_hrtimer <-__run_hrtimer mmcqd/0-1435 0d.h2 183us : _raw_spin_unlock <-hrtimer_interrupt mmcqd/0-1435 0d.h2 183us : preempt_count_sub <-_raw_spin_unlock mmcqd/0-1435 0d.h1 184us : tick_program_event <-hrtimer_interrupt mmcqd/0-1435 0d.h1 184us : clockevents_program_event <-tick_program_event mmcqd/0-1435 0d.h1 184us : ktime_get <-clockevents_program_event mmcqd/0-1435 0d.h1 185us : lapic_next_deadline <-clockevents_program_event mmcqd/0-1435 0d.h1 186us : irq_exit <-smp_apic_timer_interrupt mmcqd/0-1435 0d.h1 186us : irqtime_account_irq <-irq_exit mmcqd/0-1435 0d.h1 187us : preempt_count_sub <-irq_exit mmcqd/0-1435 0d..1 187us : __do_softirq <-irq_exit mmcqd/0-1435 0d..1 188us : msecs_to_jiffies <-__do_softirq mmcqd/0-1435 0d..1 188us : irqtime_account_irq <-__do_softirq mmcqd/0-1435 0d..1 188us : __local_bh_disable_ip <-__do_softirq mmcqd/0-1435 0d.s1 190us : preempt_count_add <-_raw_spin_lock_irq mmcqd/0-1435 0d.s2 191us+: _raw_spin_unlock_irq <-run_timer_softirq mmcqd/0-1435 0d.s1 194us : preempt_count_add <-_raw_read_lock_irqsave mmcqd/0-1435 0d.s2 195us+: _raw_read_unlock_irqrestore <-cpufreq_cpu_get mmcqd/0-1435 0d.s1 201us : preempt_count_add <-_raw_spin_lock_irqsave mmcqd/0-1435 0d.s2 202us : _raw_spin_unlock_irqrestore <-cpufreq_stats_update mmcqd/0-1435 0d.s1 203us : preempt_count_add <-_raw_spin_lock_irqsave mmcqd/0-1435 0d.s2 203us+: _raw_spin_unlock_irqrestore <-cpufreq_stat_notifier_trans mmcqd/0-1435 0d.s1 205us : preempt_count_add <-_raw_spin_lock_irqsave mmcqd/0-1435 0d.s2 205us : detach_if_pending <-mod_timer_pinned mmcqd/0-1435 0d.s2 206us : internal_add_timer <-mod_timer_pinned mmcqd/0-1435 0d.s2 207us : __internal_add_timer <-internal_add_timer