From: vincent.donnefort@arm.com
To: peterz@infradead.org, tglx@linutronix.de, linux-kernel@vger.kernel.org
Cc: valentin.schneider@arm.com,
Vincent Donnefort <vincent.donnefort@arm.com>
Subject: [PATCH 4/4] cpu/hotplug: Fix CPU down rollback
Date: Mon, 11 Jan 2021 17:10:47 +0000 [thread overview]
Message-ID: <1610385047-92151-5-git-send-email-vincent.donnefort@arm.com> (raw)
In-Reply-To: <1610385047-92151-1-git-send-email-vincent.donnefort@arm.com>
From: Vincent Donnefort <vincent.donnefort@arm.com>
After the AP brought itself down to CPUHP_TEARDOWN_CPU, the BP will finish
the job. The steps left are as followed:
+--------------------+
| CPUHP_TEARDOWN_CPU | -> If fails state is CPUHP_TEARDOWN_CPU
+--------------------+
| ATOMIC STATES | -> Cannot Fail
+--------------------+
| CPUHP_BRINGUP_CPU | -> Cannot fail
+--------------------+
| ... |
| ... | -> Can fail and rollback
| CPUHP_OFFLINE |
+--------------------+
There are, in case of failure two possibilities:
1. Failure in CPUHP_TEARDOWN_CPU, then st->state will still be
CPUHP_TEARDOWN_CPU
2. Failure between CPUHP_OFFLINE and CPUHP_BRINGUP_CPU.
For 2. The rollback will always run in the CPUHP_BRINGUP_CPU bringup
callback (bringup_cpu()) which kicks the AP back on. The latter will then
end-up setting st->state to CPUHP_AP_ONLINE_IDLE.
Checking for CPUHP_AP_ONLINE_IDLE allows then to rollback in all cases.
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
---
kernel/cpu.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index aebec3a..8b3f84e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1078,7 +1078,14 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
* to do the further cleanups.
*/
ret = cpuhp_down_callbacks(cpu, st, target);
- if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
+ if (ret && (st->state == CPUHP_AP_ONLINE_IDLE ||
+ st->state == CPUHP_TEARDOWN_CPU) &&
+ st->state < prev_state) {
+ /*
+ * After an error the state can be either:
+ * - CPUHP_TEARDOWN_CPU if this step failed.
+ * - CPUHP_AP_ONLINE_IDLE if any other failed.
+ */
cpuhp_reset_state(st, prev_state);
__cpuhp_kick_ap(st);
}
--
2.7.4
next prev parent reply other threads:[~2021-01-11 17:12 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 17:10 [PATCH 0/4] cpu/hotplug: rollback and "fail" interface fixes vincent.donnefort
2021-01-11 17:10 ` [PATCH 1/4] cpu/hotplug: Allowing to reset fail injection vincent.donnefort
2021-01-11 17:10 ` [PATCH 2/4] cpu/hotplug: CPUHP_BRINGUP_CPU exception in " vincent.donnefort
2021-01-20 12:58 ` Peter Zijlstra
2021-01-20 15:17 ` Vincent Donnefort
2021-01-20 17:30 ` Peter Zijlstra
2021-01-11 17:10 ` [PATCH 3/4] cpu/hotplug: Add cpuhp_invoke_callback_range() vincent.donnefort
2021-01-20 13:11 ` Peter Zijlstra
2021-01-20 17:54 ` Peter Zijlstra
2021-01-20 17:45 ` Peter Zijlstra
2021-01-20 17:53 ` Peter Zijlstra
2021-01-21 10:57 ` Vincent Donnefort
2021-01-21 11:18 ` Peter Zijlstra
2021-01-20 17:49 ` Peter Zijlstra
2021-01-11 17:10 ` vincent.donnefort [this message]
2021-01-21 14:57 ` [PATCH 4/4] cpu/hotplug: Fix CPU down rollback Peter Zijlstra
2021-01-21 15:43 ` Vincent Donnefort
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