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From ede4434f3a1212a45c599b20d9417bdd1f90e07c Mon Sep 17 00:00:00 2001
From: Sean Keely <sean.keely@amd.com>
Date: Wed, 15 Jul 2015 02:43:42 -0500
Subject: [PATCH 1346/4131] drm/amdkfd: Fix scheduler race in
kfd_wait_on_events sleep loop
This reapplies a fix that was accidentally reverted when cleaning
up code for upstreaming. Added a comment to explain the race
condition and how it is fixed.
Change-Id: Ic030a0f5be1d4147ce0c36b57e5526f748c3b25a
Signed-off-by: Sean Keely <sean.keely@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
---
drivers/gpu/drm/amd/amdkfd/kfd_events.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
index f565530..8debe6e 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_events.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
@@ -869,6 +869,17 @@ int kfd_wait_on_events(struct kfd_process *p,
break;
}
+ /* Set task state to interruptible sleep before
+ * checking wake-up conditions. A concurrent wake-up
+ * will put the task back into runnable state. In that
+ * case schedule_timeout will not put the task to
+ * sleep and we'll get a chance to re-check the
+ * updated conditions almost immediately. Otherwise,
+ * this race condition would lead to a soft hang or a
+ * very long sleep.
+ */
+ set_current_state(TASK_INTERRUPTIBLE);
+
if (test_event_condition(all, num_events, event_waiters)) {
if (copy_signaled_event_data(num_events,
event_waiters, events))
@@ -883,7 +894,7 @@ int kfd_wait_on_events(struct kfd_process *p,
break;
}
- timeout = schedule_timeout_interruptible(timeout);
+ timeout = schedule_timeout(timeout);
}
__set_current_state(TASK_RUNNING);
--
2.7.4
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