The patch titled
Subject: kernel/watchdog: always restore watchdog_softlockup(,hardlockup)_user_enabled after proc show
has been added to the -mm mm-nonmm-unstable branch. Its filename is
kernel-watchdog-always-restore-watchdog_softlockuphardlockup_user_enabled-after-proc-show.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kernel-watchdog-always-restore-watchdog_softlockuphardlockup_user_enabled-after-proc-show.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Tio Zhang <tiozhang@xxxxxxxxxxxxxx>
Subject: kernel/watchdog: always restore watchdog_softlockup(,hardlockup)_user_enabled after proc show
Date: Fri, 6 Sep 2024 17:47:00 +0800
Otherwise when watchdog_enabled becomes 0,
watchdog_softlockup(,hardlockup)_user_enabled will changes to 0 after proc
show.
Steps to reproduce:
step 1:
# cat /proc/sys/kernel/*watchdog
1
1
1
| name | value
|----------------------------------|--------------------------
| watchdog_enabled | 1
|----------------------------------|--------------------------
| watchdog_hardlockup_user_enabled | 1
|----------------------------------|--------------------------
| watchdog_softlockup_user_enabled | 1
|----------------------------------|--------------------------
| watchdog_user_enabled | 1
|----------------------------------|--------------------------
step 2:
# echo 0 > /proc/sys/kernel/watchdog
| name | value
|----------------------------------|--------------------------
| watchdog_enabled | 0
|----------------------------------|--------------------------
| watchdog_hardlockup_user_enabled | 1
|----------------------------------|--------------------------
| watchdog_softlockup_user_enabled | 1
|----------------------------------|--------------------------
| watchdog_user_enabled | 0
|----------------------------------|--------------------------
step 3:
# cat /proc/sys/kernel/*watchdog
0
0
0
| name | value
|----------------------------------|--------------------------
| watchdog_enabled | 0
|----------------------------------|--------------------------
| watchdog_hardlockup_user_enabled | 0
|----------------------------------|--------------------------
| watchdog_softlockup_user_enabled | 0
|----------------------------------|--------------------------
| watchdog_user_enabled | 0
|----------------------------------|--------------------------
step 4:
# echo 1 > /proc/sys/kernel/watchdog
| name | value
|----------------------------------|--------------------------
| watchdog_enabled | 0
|----------------------------------|--------------------------
| watchdog_hardlockup_user_enabled | 0
|----------------------------------|--------------------------
| watchdog_softlockup_user_enabled | 0
|----------------------------------|--------------------------
| watchdog_user_enabled | 0
|----------------------------------|--------------------------
step 5:
# cat /proc/sys/kernel/*watchdog
0
0
0
If we dont do "step 3", do "step 4" right after "step 2", it will be
| name | value
|----------------------------------|--------------------------
| watchdog_enabled | 1
|----------------------------------|--------------------------
| watchdog_hardlockup_user_enabled | 1
|----------------------------------|--------------------------
| watchdog_softlockup_user_enabled | 1
|----------------------------------|--------------------------
| watchdog_user_enabled | 1
|----------------------------------|--------------------------
then everything works correctly.
So this patch fix "step 3"'s value into
| name | value
|----------------------------------|--------------------------
| watchdog_enabled | 0
|----------------------------------|--------------------------
| watchdog_hardlockup_user_enabled | 1
|----------------------------------|--------------------------
| watchdog_softlockup_user_enabled | 1
|----------------------------------|--------------------------
| watchdog_user_enabled | 0
|----------------------------------|--------------------------
And still print 0 as before.
Link: https://lkml.kernel.org/r/20240906094700.GA30052@didi-ThinkCentre-M930t-N000
Signed-off-by: Tio Zhang <tiozhang@xxxxxxxxxxxxxx>
Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: John Ogness <john.ogness@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Krister Johansen <kjlx@xxxxxxxxxxxxxxxxxx>
Cc: Li Zhe <lizhe.67@xxxxxxxxxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Thomas WeiÃ?schuh <linux@xxxxxxxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/watchdog.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/kernel/watchdog.c~kernel-watchdog-always-restore-watchdog_softlockuphardlockup_user_enabled-after-proc-show
+++ a/kernel/watchdog.c
@@ -990,6 +990,7 @@ static int proc_watchdog_common(int whic
mutex_lock(&watchdog_mutex);
+ old = *param;
if (!write) {
/*
* On read synchronize the userspace interface. This is a
@@ -997,8 +998,8 @@ static int proc_watchdog_common(int whic
*/
*param = (watchdog_enabled & which) != 0;
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ *param = old;
} else {
- old = READ_ONCE(*param);
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (!err && old != READ_ONCE(*param))
proc_watchdog_update();
_
Patches currently in -mm which might be from tiozhang@xxxxxxxxxxxxxx are
kernel-watchdog-always-restore-watchdog_softlockuphardlockup_user_enabled-after-proc-show.patch
