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mutex: Use atomics to set current thread in recursive mutex 

Because this->thread is also read by threads that don't hold the
mutex the previous implementation was problematic (especially since
pthread_t is an opaque type of unknown length).

Fixes #654.
This commit is contained in:
Tobias Brunner 2014-07-17 10:35:42 +02:00
parent 7e433456fc
commit dbd7f4be31
1 changed files with 12 additions and 9 deletions
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21
src/libstrongswan/threading/mutex.c
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@ -23,6 +23,7 @@
#include <library.h>
#include <utils/debug.h>
#include "thread.h"
#include "condvar.h"
#include "mutex.h"
#include "lock_profiler.h"
@ -70,7 +71,7 @@ struct private_r_mutex_t {
/**
* thread which currently owns mutex
*/
pthread_t thread;
thread_t *thread;
/**
* times the current thread locked the mutex
@ -125,16 +126,16 @@ METHOD(mutex_t, unlock, void,
METHOD(mutex_t, lock_r, void,
private_r_mutex_t *this)
{
pthread_t self = pthread_self();
thread_t *self = thread_current();
if (pthread_equal(this->thread, self))
if (cas_ptr(&this->thread, self, self))
{
this->times++;
}
else
{
lock(&this->generic);
this->thread = self;
cas_ptr(&this->thread, NULL, self);
this->times = 1;
}
}
@ -144,7 +145,7 @@ METHOD(mutex_t, unlock_r, void,
{
if (--this->times == 0)
{
memset(&this->thread, 0, sizeof(this->thread));
cas_ptr(&this->thread, thread_current(), NULL);
unlock(&this->generic);
}
}
@ -220,14 +221,15 @@ METHOD(condvar_t, wait_, void,
if (mutex->recursive)
{
private_r_mutex_t* recursive = (private_r_mutex_t*)mutex;
thread_t *self = thread_current();
u_int times;
/* keep track of the number of times this thread locked the mutex */
times = recursive->times;
/* mutex owner gets cleared during condvar wait */
memset(&recursive->thread, 0, sizeof(recursive->thread));
cas_ptr(&recursive->thread, self, NULL);
pthread_cond_wait(&this->condvar, &mutex->mutex);
recursive->thread = pthread_self();
cas_ptr(&recursive->thread, NULL, self);
recursive->times = times;
}
else
@ -253,13 +255,14 @@ METHOD(condvar_t, timed_wait_abs, bool,
if (mutex->recursive)
{
private_r_mutex_t* recursive = (private_r_mutex_t*)mutex;
thread_t *self = thread_current();
u_int times;
times = recursive->times;
memset(&recursive->thread, 0, sizeof(recursive->thread));
cas_ptr(&recursive->thread, self, NULL);
timed_out = pthread_cond_timedwait(&this->condvar, &mutex->mutex,
&ts) == ETIMEDOUT;
recursive->thread = pthread_self();
cas_ptr(&recursive->thread, NULL, self);
recursive->times = times;
}
else