linux-kernel - [PATCH 0/2] freezer,sched: do not restore saved

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Message-ID: <20231120-freezer-state-multiple-thaws-v1-0-f2e1dd7ce5a2@quicinc.com>
Date:   Mon, 20 Nov 2023 09:36:30 -0800
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>, "Ingo Molnar" <mingo@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
CC:     <linux-arm-msm@...r.kernel.org>,
        Pavan Kondeti <quic_pkondeti@...cinc.com>,
        "Aiqun Yu (Maria)" <quic_aiquny@...cinc.com>,
        <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Elliot Berman <quic_eberman@...cinc.com>,
        Abhijeet Dharmapurikar <quic_adharmap@...cinc.com>
Subject: [PATCH 0/2] freezer,sched: do not restore saved_state of a thawed
 task

This series applies couple fixes to commit 8f0eed4a78a8 ("freezer,sched:
Use saved_state to reduce some spurious wakeups") which was found while
testing with legacy cgroup freezer. My original testing was only with
system-wide freezer. We found that thaw_task could be called on a task
which was already frozen. Prior to commit 8f0eed4a78a8 ("freezer,sched:
Use saved_state to reduce some spurious wakeups"), this wasn't an issue
as kernel would try to wake up TASK_FROZEN, which wouldn't match the
thawed task state, and no harm done to task. After commit 8f0eed4a78a8
("freezer,sched: Use saved_state to reduce some spurious wakeups"), it
was possible to overwrite the state of thawed task.

To: Rafael J. Wysocki <rafael@...nel.org>
To: Pavel Machek <pavel@....cz>
To: Ingo Molnar <mingo@...nel.org>
To: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc:  <linux-arm-msm@...r.kernel.org>
Cc: Pavan Kondeti <quic_pkondeti@...cinc.com>
Cc: Aiqun Yu (Maria) <quic_aiquny@...cinc.com>
Cc:  <linux-pm@...r.kernel.org>
Cc:  <linux-kernel@...r.kernel.org>
Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>

Originally sent to only linux-arm-msm, resending to correct authors.
- Link to v1: https://lore.kernel.org/r/20231120-freezer-state-multiple-thaws-v1-0-a4c453f50745@quicinc.com

---
Elliot Berman (2):
      freezer,sched: do not restore saved_state of a thawed task
      freezer,sched: clean saved_state when restoring it during thaw

 kernel/freezer.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
base-commit: 6d7e4782bcf549221b4ccfffec2cf4d1a473f1a3
change-id: 20231108-freezer-state-multiple-thaws-7a3a8d9dadb3

Best regards,
-- 
Elliot Berman <quic_eberman@...cinc.com>