The patch titled
Subject: watchdog: fix error handling in proc_watchdog_thresh()
has been added to the -mm tree. Its filename is
watchdog-fix-error-handling-in-proc_watchdog_thresh.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/watchdog-fix-error-handling-in-proc_watchdog_thresh.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/watchdog-fix-error-handling-in-proc_watchdog_thresh.patch
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------------------------------------------------------
From: Ulrich Obergfell <uobergfe@xxxxxxxxxx>
Subject: watchdog: fix error handling in proc_watchdog_thresh()
The original watchdog_park_threads() function that was introduced by
81a4beef91ba4a9 ("watchdog: introduce watchdog_park_threads() and
watchdog_unpark_threads()") takes a very simple approach to handle errors
returned by kthread_park(): It attempts to roll back all watchdog threads
to the unparked state. However, this may be undesired behaviour from the
perspective of the caller which may want to handle errors as appropriate
in its specific context. Currently, there are two possible call chains:
- watchdog suspend/resume interface
lockup_detector_suspend
watchdog_park_threads
- write to parameters in /proc/sys/kernel
proc_watchdog_update
watchdog_enable_all_cpus
update_watchdog_all_cpus
watchdog_park_threads
Instead of 'blindly' attempting to unpark the watchdog threads if a
kthread_park() call fails, the new approach is to disable the lockup
detectors in the above call chains. Failure becomes visible to the user
as follows:
- error messages from lockup_detector_suspend()
or watchdog_enable_all_cpus()
- the state that can be read from /proc/sys/kernel/watchdog_enabled
- the 'write' system call in the latter call chain returns an error
This patch (of 5):
Restore the previous value of watchdog_thresh _and_ sample_period if
proc_watchdog_update() returns an error. The variables must be consistent
to avoid false positives of the lockup detectors.
Signed-off-by: Ulrich Obergfell <uobergfe@xxxxxxxxxx>
Reviewed-by: Aaron Tomlin <atomlin@xxxxxxxxxx>
Cc: Don Zickus <dzickus@xxxxxxxxxx>
Cc: Ulrich Obergfell <uobergfe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/watchdog.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff -puN kernel/watchdog.c~watchdog-fix-error-handling-in-proc_watchdog_thresh kernel/watchdog.c
--- a/kernel/watchdog.c~watchdog-fix-error-handling-in-proc_watchdog_thresh
+++ a/kernel/watchdog.c
@@ -914,13 +914,14 @@ int proc_watchdog_thresh(struct ctl_tabl
goto out;
/*
- * Update the sample period.
- * Restore 'watchdog_thresh' on failure.
+ * Update the sample period. Restore on failure.
*/
set_sample_period();
err = proc_watchdog_update();
- if (err)
+ if (err) {
watchdog_thresh = old;
+ set_sample_period();
+ }
out:
mutex_unlock(&watchdog_proc_mutex);
return err;
_
Patches currently in -mm which might be from uobergfe@xxxxxxxxxx are
watchdog-fix-error-handling-in-proc_watchdog_thresh.patch
watchdog-move-watchdog_disable_all_cpus-outside-of-ifdef.patch
watchdog-implement-error-handling-in-update_watchdog_all_cpus-and-callers.patch
watchdog-implement-error-handling-in-lockup_detector_suspend.patch
watchdog-do-not-unpark-threads-in-watchdog_park_threads-on-error.patch
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