linux-kernel - [(RESEND) PATCH] sched: fix RT task-wakeup logic

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080428162747.5784.82343.stgit@novell1.haskins.net>
Date:	Mon, 28 Apr 2008 12:30:29 -0400
From:	Gregory Haskins <ghaskins@...ell.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Gregory Haskins <ghaskins@...ell.com>,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: [(RESEND) PATCH] sched: fix RT task-wakeup logic

Hi Ingo,
  Im not sure if this patch fell through the cracks, or if you didn't like it
  for some reason.  If you can, please ACK/NACK it so I know if you have
  reviewed it or not.  Thanks!

(This applies to sched-devel, and should be considered a bug fix for 25.y and
the 26 merge window)

-Greg

------------------------------
sched: fix RT task-wakeup logic

Dmitry Adamushko pointed out a logic error in task_wake_up_rt() where we
will always evaluate to "true".  You can find the thread here:

http://lkml.org/lkml/2008/4/22/296

In reality, we only want to try to push tasks away when a wake up request is
not going to preempt the current task.  So lets fix it.

Note: We introduce test_tsk_need_resched() instead of open-coding the flag
check so that the merge-conflict with -rt should help remind us that we
may need to support NEEDS_RESCHED_DELAYED in the future, too.

Signed-off-by: Gregory Haskins <ghaskins@...ell.com>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
Acked-by: Dmitry Adamushko <dmitry.adamushko@...il.com>
CC: Ingo Molnar <mingo@...e.hu>
---

 include/linux/sched.h |    7 ++++++-
 kernel/sched_rt.c     |    7 +++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 949bd54..55d4bd4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1966,6 +1966,11 @@ static inline void clear_tsk_need_resched(struct task_struct *tsk)
 	clear_tsk_thread_flag(tsk,TIF_NEED_RESCHED);
 }
 
+static inline int test_tsk_need_resched(struct task_struct *tsk)
+{
+	return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED));
+}
+
 static inline int signal_pending(struct task_struct *p)
 {
 	return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING));
@@ -1980,7 +1985,7 @@ static inline int fatal_signal_pending(struct task_struct *p)
 
 static inline int need_resched(void)
 {
-	return unlikely(test_thread_flag(TIF_NEED_RESCHED));
+	return unlikely(test_tsk_need_resched(current));
 }
 
 /*
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 79e5ad5..ae6b0e6 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1058,11 +1058,14 @@ static void post_schedule_rt(struct rq *rq)
 	}
 }
 
-
+/*
+ * If we are not running and we are not going to reschedule soon, we should
+ * try to push tasks away now
+ */
 static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
 {
 	if (!task_running(rq, p) &&
-	    (p->prio >= rq->rt.highest_prio) &&
+	    !test_tsk_need_resched(rq->curr) &&
 	    rq->rt.overloaded)
 		push_rt_tasks(rq);
 }

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/