Commit 56467c76 authored May 06, 2013 by Colin Cross Committed by Rafael J. Wysocki May 12, 2013

futex: use freezable blocking call



Avoid waking up every thread sleeping in a futex_wait call during
suspend and resume by calling a freezable blocking call.  Previous
patches modified the freezer to avoid sending wakeups to threads
that are blocked in freezable blocking calls.

This call was selected to be converted to a freezable call because
it doesn't hold any locks or release any resources when interrupted
that might be needed by another freezing task or a kernel driver
during suspend, and is a common site where idle userspace tasks are
blocked.

Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent 9745cdb3

kernel/futex.c

+2 −1

Original line number	Original line	Diff line number	Diff line
	@@ -61,6 +61,7 @@
	#include <linux/nsproxy.h>		#include <linux/nsproxy.h>
	#include <linux/ptrace.h>		#include <linux/ptrace.h>
	#include <linux/sched/rt.h>		#include <linux/sched/rt.h>
			#include <linux/freezer.h>

	#include <asm/futex.h>		#include <asm/futex.h>

	@@ -1807,7 +1808,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket hb, struct futex_q q,
	* is no timeout, or if it has yet to expire.		* is no timeout, or if it has yet to expire.
	*/		*/
	if (!timeout \|\| timeout->task)		if (!timeout \|\| timeout->task)
	schedule();		freezable_schedule();
	}		}
	__set_current_state(TASK_RUNNING);		__set_current_state(TASK_RUNNING);
	}		}