From: Nadav Har'El <n...@scylladb.com>
Committer: Nadav Har'El <n...@scylladb.com>
Branch: master
sched: ignore thread in wrong wakeup queue
With this patch, if handle_incoming_wakeups() discovers in a CPU's wakeup
queue a thread which does not actually belong to it, it simply ignores it.
This case should never happen. However, in a following patch we add the
ability to pin (migrate) a waiting thread, and that operating might race
with a wake() of the same thread, resulting in the thread remaining on
the old cpu's wakeup queues, and we better ignore it there.
Signed-off-by: Nadav Har'El <n...@scylladb.com>
Message-Id: <1469628899-5537-1-git-send-email-...@scylladb.com>
---
diff --git a/core/sched.cc b/core/sched.cc
--- a/core/sched.cc
+++ b/core/sched.cc
@@ -443,6 +443,9 @@ void cpu::handle_incoming_wakeups()
// Special case of current thread being woken before
// having a chance to be scheduled out.
t._detached_state->st.store(thread::status::running);
+ } else if (t.tcpu() != this) {
+ // Thread was woken on the wrong cpu. Can be a
side-effect
+ // of sched::thread::pin(thread*, cpu*). Do nothing.
} else {
t._detached_state->st.store(thread::status::queued);
// Make sure the CPU-local runtime measure is suitably
--
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