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watchdog/core: Rework CPU hotplug locking

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The watchdog proc interface causes extensive recursive locking of the CPU
hotplug percpu rwsem, which is deadlock prone.

Replace the get/put_online_cpus() pairs with cpu_hotplug_disable()/enable()
calls for now. Later patches will remove that requirement completely.

Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Link: http://lkml.kernel.org/r/20170912194146.568079057@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Thomas Gleixner 2017-09-12 21:37:00 +02:00 committed by Ingo Molnar
parent 5490125d77
commit b7a349819d
1 changed files with 6 additions and 6 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

12
kernel/watchdog.c
View file

@ -703,7 +703,7 @@ static int proc_watchdog_common(int which, struct ctl_table *table, int write,
int err, old, new; int err, old, new;
int *watchdog_param = (int *)table->data; int *watchdog_param = (int *)table->data;
get_online_cpus(); cpu_hotplug_disable();
mutex_lock(&watchdog_proc_mutex); mutex_lock(&watchdog_proc_mutex);
/* /*
@ -752,7 +752,7 @@ static int proc_watchdog_common(int which, struct ctl_table *table, int write,
} }
out: out:
mutex_unlock(&watchdog_proc_mutex); mutex_unlock(&watchdog_proc_mutex);
put_online_cpus(); cpu_hotplug_enable();
return err; return err;
} }
@ -794,7 +794,7 @@ int proc_watchdog_thresh(struct ctl_table *table, int write,
{ {
int err, old, new; int err, old, new;
get_online_cpus(); cpu_hotplug_disable();
mutex_lock(&watchdog_proc_mutex); mutex_lock(&watchdog_proc_mutex);
old = ACCESS_ONCE(watchdog_thresh); old = ACCESS_ONCE(watchdog_thresh);
@ -818,7 +818,7 @@ int proc_watchdog_thresh(struct ctl_table *table, int write,
} }
out: out:
mutex_unlock(&watchdog_proc_mutex); mutex_unlock(&watchdog_proc_mutex);
put_online_cpus(); cpu_hotplug_enable();
return err; return err;
} }
@ -833,7 +833,7 @@ int proc_watchdog_cpumask(struct ctl_table *table, int write,
{ {
int err; int err;
get_online_cpus(); cpu_hotplug_disable();
mutex_lock(&watchdog_proc_mutex); mutex_lock(&watchdog_proc_mutex);
err = proc_do_large_bitmap(table, write, buffer, lenp, ppos); err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
@ -856,7 +856,7 @@ int proc_watchdog_cpumask(struct ctl_table *table, int write,
} }
mutex_unlock(&watchdog_proc_mutex); mutex_unlock(&watchdog_proc_mutex);
put_online_cpus(); cpu_hotplug_enable();
return err; return err;
} }