Commit b7a34981 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

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: default avatarBorislav Petkov <bp@alien8.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarDon 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: default avatarIngo Molnar <mingo@kernel.org>
parent 5490125d

kernel/watchdog.c

+6 −6
Original line number Diff line number Diff line
@@ -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;

}