linux-kernel - [PATCH 4.16 096/113] cpufreq: powernv: Fix hardlockup due to synchronous smp

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Message-Id: <20180430184019.264163678@linuxfoundation.org>
Date:   Mon, 30 Apr 2018 12:25:07 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nicholas Piggin <npiggin@...il.com>,
        Pridhiviraj Paidipeddi <ppaidipe@...ux.vnet.ibm.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.16 096/113] cpufreq: powernv: Fix hardlockup due to synchronous smp_call in timer interrupt

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>

commit c0f7f5b6c69107ca92909512533e70258ee19188 upstream.

gpstate_timer_handler() uses synchronous smp_call to set the pstate
on the requested core. This causes the below hard lockup:

  smp_call_function_single+0x110/0x180 (unreliable)
  smp_call_function_any+0x180/0x250
  gpstate_timer_handler+0x1e8/0x580
  call_timer_fn+0x50/0x1c0
  expire_timers+0x138/0x1f0
  run_timer_softirq+0x1e8/0x270
  __do_softirq+0x158/0x3e4
  irq_exit+0xe8/0x120
  timer_interrupt+0x9c/0xe0
  decrementer_common+0x114/0x120
  -- interrupt: 901 at doorbell_global_ipi+0x34/0x50
  LR = arch_send_call_function_ipi_mask+0x120/0x130
  arch_send_call_function_ipi_mask+0x4c/0x130
  smp_call_function_many+0x340/0x450
  pmdp_invalidate+0x98/0xe0
  change_huge_pmd+0xe0/0x270
  change_protection_range+0xb88/0xe40
  mprotect_fixup+0x140/0x340
  SyS_mprotect+0x1b4/0x350
  system_call+0x58/0x6c

One way to avoid this is removing the smp-call. We can ensure that the
timer always runs on one of the policy-cpus. If the timer gets
migrated to a cpu outside the policy then re-queue it back on the
policy->cpus. This way we can get rid of the smp-call which was being
used to set the pstate on the policy->cpus.

Fixes: 7bc54b652f13 ("timers, cpufreq/powernv: Initialize the gpstate timer as pinned")
Cc: stable@...r.kernel.org # v4.8+
Reported-by: Nicholas Piggin <npiggin@...il.com>
Reported-by: Pridhiviraj Paidipeddi <ppaidipe@...ux.vnet.ibm.com>
Signed-off-by: Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
Acked-by: Nicholas Piggin <npiggin@...il.com>
Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
Acked-by: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/cpufreq/powernv-cpufreq.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -679,6 +679,16 @@ void gpstate_timer_handler(struct timer_
 
 	if (!spin_trylock(&gpstates->gpstate_lock))
 		return;
+	/*
+	 * If the timer has migrated to the different cpu then bring
+	 * it back to one of the policy->cpus
+	 */
+	if (!cpumask_test_cpu(raw_smp_processor_id(), policy->cpus)) {
+		gpstates->timer.expires = jiffies + msecs_to_jiffies(1);
+		add_timer_on(&gpstates->timer, cpumask_first(policy->cpus));
+		spin_unlock(&gpstates->gpstate_lock);
+		return;
+	}
 
 	/*
 	 * If PMCR was last updated was using fast_swtich then
@@ -718,10 +728,8 @@ void gpstate_timer_handler(struct timer_
 	if (gpstate_idx != gpstates->last_lpstate_idx)
 		queue_gpstate_timer(gpstates);
 
+	set_pstate(&freq_data);
 	spin_unlock(&gpstates->gpstate_lock);
-
-	/* Timer may get migrated to a different cpu on cpu hot unplug */
-	smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
 }
 
 /*