[PATCH RT 22/25][RFC 3.0.23-rt39-rc1] sched/rt: Fix wait_task_interactive() to test rt_spin_lock state

Steven Rostedt
2012-03-06T16:16:58Z

[-- Attachment #1: 0022-sched-rt-Fix-wait_task_interactive-to-test-rt_spin_l.patch --]
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From: Steven Rostedt <rostedt@goodmis.org>

The wait_task_interactive() will have a task sleep waiting for another
task to have a certain state. But it ignores the rt_spin_locks state
and can return with an incorrect result if the task it is waiting
for is blocked on a rt_spin_lock() and is waking up.

The rt_spin_locks save the tasks state in the saved_state field
and the wait_task_interactive() must also test that state.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Carsten Emde <C.Emde@osadl.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clark Williams <clark.williams@gmail.com>
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/20120301190345.979435764@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/sched.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index e5ef7a8..df30481 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2284,7 +2284,8 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state)
* is actually now running somewhere else!
*/
while (task_running(rq, p)) {
- if (match_state && unlikely(p->state != match_state))
+ if (match_state && unlikely(p->state != match_state)
+ && unlikely(p->saved_state != match_state))
return 0;
cpu_relax();
}
@@ -2299,7 +2300,8 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state)
running = task_running(rq, p);
on_rq = p->on_rq;
ncsw = 0;
- if (!match_state || p->state == match_state)
+ if (!match_state || p->state == match_state
+ || p->saved_state == match_state)
ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
task_rq_unlock(rq, p, &flags);

--
1.7.8.3