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Subject[tip:core/locking] futex: Use freezable blocking call
Commit-ID:  88c8004fd3a5fdd2378069de86b90b21110d33a4
Gitweb: http://git.kernel.org/tip/88c8004fd3a5fdd2378069de86b90b21110d33a4
Author: Colin Cross <ccross@android.com>
AuthorDate: Wed, 1 May 2013 18:35:05 -0700
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 25 Jun 2013 23:11:19 +0200

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.

Signed-off-by: Colin Cross <ccross@android.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: arve@android.com
Cc: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Link: http://lkml.kernel.org/r/1367458508-9133-8-git-send-email-ccross@android.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/futex.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 49dacfb..c3a1a55 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -62,6 +62,7 @@
#include <linux/ptrace.h>
#include <linux/sched/rt.h>
#include <linux/hugetlb.h>
+#include <linux/freezer.h>

#include <asm/futex.h>

@@ -1808,7 +1809,7 @@ 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.
*/
if (!timeout || timeout->task)
- schedule();
+ freezable_schedule();
}
__set_current_state(TASK_RUNNING);
}

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