linux-kernel - [PATCH] PM: hibernate: Freeze kernel threads in software

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Date:   Thu, 23 Apr 2020 20:40:16 -0700
From:   Dexuan Cui <decui@...rosoft.com>
To:     linux-pm@...r.kernel.org, rjw@...ysocki.net, len.brown@...el.com,
        pavel@....cz, bvanassche@....org, mikelley@...rosoft.com,
        longli@...rosoft.com
Cc:     linux-kernel@...r.kernel.org, ming.lei@...hat.com,
        wei.liu@...nel.org, sthemmin@...rosoft.com, haiyangz@...rosoft.com,
        kys@...rosoft.com, Dexuan Cui <decui@...rosoft.com>,
        stable@...r.kernel.org
Subject: [PATCH] PM: hibernate: Freeze kernel threads in software_resume()

Currently the kernel threads are not frozen in software_resume(), so
between dpm_suspend_start(PMSG_QUIESCE) and resume_target_kernel(),
system_freezable_power_efficient_wq can still try to submit SCSI
commands and this can cause a panic since the low level SCSI driver
(e.g. hv_storvsc) has quiesced the SCSI adapter and can not accept
any SCSI commands: https://lkml.org/lkml/2020/4/10/47

At first I posted a fix (https://lkml.org/lkml/2020/4/21/1318) trying
to resolve the issue from hv_storvsc, but with the help of
Bart Van Assche, I realized it's better to fix software_resume(),
since this looks like a generic issue, not only pertaining to SCSI.

Cc: Bart Van Assche <bvanassche@....org>
Cc: stable@...r.kernel.org
Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---
 kernel/power/hibernate.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 86aba8706b16..30bd28d1d418 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -898,6 +898,13 @@ static int software_resume(void)
 	error = freeze_processes();
 	if (error)
 		goto Close_Finish;
+
+	error = freeze_kernel_threads();
+	if (error) {
+		thaw_processes();
+		goto Close_Finish;
+	}
+
 	error = load_image_and_restore();
 	thaw_processes();
  Finish:
-- 
2.19.1