From ec1d09c018eead8ca2c958163a72f44260b91e9a Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@cloudius-systems.com>
Date: Mon, 25 Feb 2013 17:25:33 +0200
Subject: [PATCH] mutex: allow recusrive locking
prex code depends on this.
TODO: make it optional
---
core/mutex.cc | 19 +++++++++++++------
include/osv/mutex.h | 2 ++
2 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/core/mutex.cc b/core/mutex.cc
index e1a52d349..ff5b449e5 100644
--- a/core/mutex.cc
+++ b/core/mutex.cc
@@ -14,8 +14,9 @@ extern "C" void mutex_lock(mutex_t *mutex)
w.thread = sched::thread::current();
spin_lock(&mutex->_wait_lock);
- if (!mutex->_owner) {
+ if (!mutex->_owner || mutex->_owner == w.thread) {
mutex->_owner = w.thread;
+ ++mutex->_depth;
spin_unlock(&mutex->_wait_lock);
return;
}
@@ -43,8 +44,9 @@ extern "C" bool mutex_trylock(mutex_t *mutex)
{
bool ret = false;
spin_lock(&mutex->_wait_lock);
- if (!mutex->_owner) {
+ if (!mutex->_owner || mutex->_owner == sched::thread::current()) {
mutex->_owner = sched::thread::current();
+ ++mutex->_depth;
ret = true;
}
spin_unlock(&mutex->_wait_lock);
@@ -54,11 +56,16 @@ extern "C" bool mutex_trylock(mutex_t *mutex)
extern "C" void mutex_unlock(mutex_t *mutex)
{
spin_lock(&mutex->_wait_lock);
- if (mutex->_wait_list.first) {
- mutex->_owner = mutex->_wait_list.first->thread;
- mutex->_wait_list.first->thread->wake();
+ if (mutex->_depth == 1) {
+ if (mutex->_wait_list.first) {
+ mutex->_owner = mutex->_wait_list.first->thread;
+ mutex->_wait_list.first->thread->wake();
+ } else {
+ mutex->_owner = nullptr;
+ --mutex->_depth;
+ }
} else {
- mutex->_owner = nullptr;
+ --mutex->_depth;
}
spin_unlock(&mutex->_wait_lock);
}
diff --git a/include/osv/mutex.h b/include/osv/mutex.h
index 63ba016af..8c9c4f34a 100644
--- a/include/osv/mutex.h
+++ b/include/osv/mutex.h
@@ -21,6 +21,7 @@ static inline void spinlock_init(spinlock_t *sl)
struct cmutex {
spinlock_t _wait_lock;
+ unsigned _depth;
void *_owner;
struct wait_list {
struct waiter *first;
@@ -38,6 +39,7 @@ void mutex_unlock(mutex_t* m);
static __always_inline void mutex_init(mutex_t* m)
{
+ m->_depth = 0;
m->_owner = 0;
m->_wait_list.first = 0;
m->_wait_list.last = 0;
--
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