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watchdog/core: Rework CPU hotplug locking 

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