From db30e72069f9bdddda33b824c0e4a0fa3f6e51ce Mon Sep 17 00:00:00 2001
From: Dominik Gleich <dominik.gleich@memgraph.io>
Date: Fri, 14 Apr 2017 16:56:27 +0200
Subject: [PATCH] Change back to seq_cst memory ordering.
Summary: This probably made the sl_simulation test hang. We'll update it to this for now and see how it will behave in the future.
Reviewers: buda
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D284
---
src/threading/sync/futex.hpp | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/src/threading/sync/futex.hpp b/src/threading/sync/futex.hpp
index 648baa14f..4a73694a9 100644
--- a/src/threading/sync/futex.hpp
+++ b/src/threading/sync/futex.hpp
@@ -67,7 +67,7 @@ class Futex {
bool try_lock() {
// we took the lock if we stored the LOCKED state and previous
// state was UNLOCKED
- return mutex.state.locked.exchange(LOCKED, std::memory_order_acquire) ==
+ return mutex.state.locked.exchange(LOCKED, std::memory_order_seq_cst) ==
UNLOCKED;
}
@@ -83,7 +83,7 @@ class Futex {
// the lock is contended, go to sleep. when someone
// wakes you up, try taking the lock again
- while (mutex.all.exchange(LOCKED_CONTENDED, std::memory_order_acquire) &
+ while (mutex.all.exchange(LOCKED_CONTENDED, std::memory_order_seq_cst) &
LOCKED) {
// wait in the kernel for someone to wake us up when unlocking
auto status = futex_wait(LOCKED_CONTENDED, timeout);
@@ -99,26 +99,26 @@ class Futex {
// if we're locked and uncontended, try to unlock the mutex before
// it becomes contended
- if (mutex.all.load(std::memory_order_acquire) == LOCKED &&
+ if (mutex.all.load(std::memory_order_seq_cst) == LOCKED &&
mutex.all.compare_exchange_strong(state, UNLOCKED,
- std::memory_order_release,
- std::memory_order_relaxed))
+ std::memory_order_seq_cst,
+ std::memory_order_seq_cst))
return;
// we are contended, just release the lock
- mutex.state.locked.store(UNLOCKED, std::memory_order_release);
+ mutex.state.locked.store(UNLOCKED, std::memory_order_seq_cst);
// spin and hope someone takes a lock so we don't have to wake up
// anyone because that's quite expensive
for (size_t i = 0; i < UNLOCK_RETRIES; ++i) {
// if someone took the lock, we're ok
- if (is_locked(std::memory_order_acquire)) return;
+ if (is_locked(std::memory_order_seq_cst)) return;
relax();
}
// store that we are becoming uncontended
- mutex.state.contended.store(UNCONTENDED, std::memory_order_release);
+ mutex.state.contended.store(UNCONTENDED, std::memory_order_seq_cst);
// we need to wake someone up
futex_wake(LOCKED);