sergiotarxz/nuttx
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
206cd96426
nuttx/libs/libc/misc/lib_mutex.c
Gregory Nutt 8868c58720 Fix Deadloop in VFS if CONFIG_CANCELLATION_POINTS is enabled 
If cancellation points are enabled, then the following logic is activated in sem_wait().  This causes ECANCELED to be returned every time that sem_wait is called.

    int sem_wait(FAR sem_t *sem)
    {
      ...

      /* sem_wait() is a cancellation point */

      if (enter_cancellation_point())
        {
    #ifdef CONFIG_CANCELLATION_POINTS
          /* If there is a pending cancellation, then do not perform
           * the wait.  Exit now with ECANCELED.
           */

          errcode = ECANCELED;
          goto errout_with_cancelpt;
    #endif
        }
      ...

Normally this works fine.  sem_wait() is the OS API called by the application and will cancel the thread just before it returns to the application.  Since it is cancellation point, it should never be called from within the OS.

There there is is one perverse cases where sem_wait() may be nested within another cancellation point.  If open() is called, it will attempt to lock a VFS data structure and will eventually call nxmutex_lock().  nxmutex_lock() waits on a semaphore:

   int nxmutex_lock(FAR mutex_t *mutex)
   {
     ...

     for (; ; )
       {
         /* Take the semaphore (perhaps waiting) */

         ret = _SEM_WAIT(&mutex->sem);
         if (ret >= 0)
           {
             mutex->holder = _SCHED_GETTID();
             break;
           }

         ret = _SEM_ERRVAL(ret);
         if (ret != -EINTR && ret != -ECANCELED)
           {
             break;
           }
       }
   ...
}

In the FLAT build, _SEM_WAIT expands to sem_wait().  That causes the error in the logic:  It should always expand to nxsem_wait().  That is because sem_wait() is cancellation point and should never be called from with the OS or the C library internally.

The failure occurs because the cancellation point logic in sem_wait() returns -ECANCELED (via _SEM_ERRVAL) because sem_wait() is nested; it needs to return the -ECANCELED error to the outermost cancellation point which is open() in this case.  Returning -ECANCELED then causes an infinite loop to occur in nxmutex_lock().

The correct behavior in this case is to call nxsem_wait() instead of sem_wait().  nxsem_wait() is identical to sem_wait() except that it is not a cancelation point.  It will return -ECANCELED if the thread is canceled, but only once.  So no infinite loop results.

In addition, an nxsem_wait() system call was added to support the call from nxmutex_lock().

This resolves Issue #9695
2023-07-06 14:20:29 -03:00

769 lines
21 KiB
C
Raw Blame History

/****************************************************************************
* libs/libc/misc/lib_mutex.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <errno.h>
#include <nuttx/sched.h>
#include <nuttx/clock.h>
#include <nuttx/mutex.h>
#include <nuttx/semaphore.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define NXMUTEX_RESET ((pid_t)-2)
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: nxmutex_is_reset
*
* Description:
* This function check whether the mutex is reset
*
* Parameters:
* mutex - mutex descriptor.
*
* Return Value:
*
****************************************************************************/
static bool nxmutex_is_reset(FAR mutex_t *mutex)
{
return mutex->holder == NXMUTEX_RESET;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxmutex_init
*
* Description:
* This function initializes the UNNAMED mutex. Following a
* successful call to nxmutex_init(), the mutex may be used in subsequent
* calls to nxmutex_lock(), nxmutex_unlock(), and nxmutex_trylock(). The
* mutex remains usable until it is destroyed.
*
* Parameters:
* mutex - Semaphore to be initialized
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
*
****************************************************************************/
int nxmutex_init(FAR mutex_t *mutex)
{
int ret = _SEM_INIT(&mutex->sem, 0, 1);
if (ret < 0)
{
return _SEM_ERRVAL(ret);
}
mutex->holder = NXMUTEX_NO_HOLDER;
#ifdef CONFIG_PRIORITY_INHERITANCE
_SEM_SETPROTOCOL(&mutex->sem, SEM_TYPE_MUTEX | SEM_PRIO_INHERIT);
#else
_SEM_SETPROTOCOL(&mutex->sem, SEM_TYPE_MUTEX);
#endif
return ret;
}
/****************************************************************************
* Name: nxmutex_destroy
*
* Description:
* This function initializes the UNNAMED mutex. Following a
* successful call to nxmutex_init(), the mutex may be used in subsequent
* calls to nxmutex_lock(), nxmutex_unlock(), and nxmutex_trylock(). The
* mutex remains usable until it is destroyed.
*
* Parameters:
* mutex - Semaphore to be destroyed
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
*
****************************************************************************/
int nxmutex_destroy(FAR mutex_t *mutex)
{
int ret = _SEM_DESTROY(&mutex->sem);
if (ret < 0)
{
return _SEM_ERRVAL(ret);
}
mutex->holder = NXMUTEX_NO_HOLDER;
return ret;
}
/****************************************************************************
* Name: nxmutex_is_hold
*
* Description:
* This function check whether the caller hold the mutex
* referenced by 'mutex'.
*
* Parameters:
* mutex - mutex descriptor.
*
* Return Value:
*
****************************************************************************/
bool nxmutex_is_hold(FAR mutex_t *mutex)
{
return mutex->holder == _SCHED_GETTID();
}
/****************************************************************************
* Name: nxmutex_is_locked
*
* Description:
* This function get the lock state the mutex referenced by 'mutex'.
*
* Parameters:
* mutex - mutex descriptor.
*
* Return Value:
*
****************************************************************************/
bool nxmutex_is_locked(FAR mutex_t *mutex)
{
int cnt;
int ret;
ret = _SEM_GETVALUE(&mutex->sem, &cnt);
return ret >= 0 && cnt < 1;
}
/****************************************************************************
* Name: nxmutex_lock
*
* Description:
* This function attempts to lock the mutex referenced by 'mutex'. The
* mutex is implemented with a semaphore, so if the semaphore value is
* (<=) zero, then the calling task will not return until it successfully
* acquires the lock.
*
* Parameters:
* mutex - mutex descriptor.
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
****************************************************************************/
int nxmutex_lock(FAR mutex_t *mutex)
{
int ret;
DEBUGASSERT(!nxmutex_is_hold(mutex));
for (; ; )
{
/* Take the semaphore (perhaps waiting) */
ret = nxsem_wait(&mutex->sem);
if (ret >= 0)
{
mutex->holder = _SCHED_GETTID();
break;
}
else if (ret != -EINTR && ret != -ECANCELED)
{
break;
}
}
return ret;
}
/****************************************************************************
* Name: nxmutex_trylock
*
* Description:
* This function locks the mutex only if the mutex is currently not locked.
* If the mutex has been locked already, the call returns without blocking.
*
* Parameters:
* mutex - mutex descriptor.
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
* -EINVAL - Invalid attempt to lock the mutex
* -EAGAIN - The mutex is not available.
*
****************************************************************************/
int nxmutex_trylock(FAR mutex_t *mutex)
{
int ret;
DEBUGASSERT(!nxmutex_is_hold(mutex));
ret = _SEM_TRYWAIT(&mutex->sem);
if (ret < 0)
{
return _SEM_ERRVAL(ret);
}
mutex->holder = _SCHED_GETTID();
return ret;
}
/****************************************************************************
* Name: nxmutex_timedlock
*
* Description:
* This function attempts to lock the mutex . If the mutex value
* is (<=) zero,then the calling task will not return until it
* successfully acquires the lock or timed out
*
* Input Parameters:
* mutex - Mutex object
* timeout - The time when mutex lock timed out
*
* Returned Value:
* OK The mutex successfully acquires
* EINVAL The mutex argument does not refer to a valid mutex. Or the
* thread would have blocked, and the abstime parameter specified
* a nanoseconds field value less than zero or greater than or
* equal to 1000 million.
* ETIMEDOUT The mutex could not be locked before the specified timeout
* expired.
* EDEADLK A deadlock condition was detected.
*
****************************************************************************/
int nxmutex_timedlock(FAR mutex_t *mutex, unsigned int timeout)
{
int ret;
struct timespec now;
struct timespec delay;
struct timespec rqtp;
clock_gettime(CLOCK_MONOTONIC, &now);
clock_ticks2time(MSEC2TICK(timeout), &delay);
clock_timespec_add(&now, &delay, &rqtp);
/* Wait until we get the lock or until the timeout expires */
do
{
ret = _SEM_CLOCKWAIT(&mutex->sem, CLOCK_MONOTONIC, &rqtp);
if (ret < 0)
{
ret = _SEM_ERRVAL(ret);
}
}
while (ret == -EINTR || ret == -ECANCELED);
if (ret >= 0)
{
mutex->holder = _SCHED_GETTID();
}
return ret;
}
/****************************************************************************
* Name: nxmutex_unlock
*
* Description:
* This function attempts to unlock the mutex referenced by 'mutex'.
*
* Parameters:
* mutex - mutex descriptor.
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
* Assumptions:
* This function may be called from an interrupt handler.
*
****************************************************************************/
int nxmutex_unlock(FAR mutex_t *mutex)
{
int ret;
if (nxmutex_is_reset(mutex))
{
return OK;
}
DEBUGASSERT(nxmutex_is_hold(mutex));
mutex->holder = NXMUTEX_NO_HOLDER;
ret = _SEM_POST(&mutex->sem);
if (ret < 0)
{
mutex->holder = _SCHED_GETTID();
ret = _SEM_ERRVAL(ret);
}
return ret;
}
/****************************************************************************
* Name: nxmutex_reset
*
* Description:
* This function reset lock state.
*
* Parameters:
* mutex - mutex descriptor.
*
****************************************************************************/
#if defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__)
void nxmutex_reset(FAR mutex_t *mutex)
{
mutex->holder = NXMUTEX_RESET;
nxsem_reset(&mutex->sem, 1);
}
#endif
/****************************************************************************
* Name: nxmutex_breaklock
*
* Description:
* This function attempts to break the mutex
*
* Parameters:
* mutex - Mutex descriptor.
* locked - Is the mutex break success
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
****************************************************************************/
int nxmutex_breaklock(FAR mutex_t *mutex, FAR bool *locked)
{
int ret = OK;
*locked = false;
if (nxmutex_is_hold(mutex))
{
ret = nxmutex_unlock(mutex);
if (ret >= 0)
{
*locked = true;
}
}
return ret;
}
/****************************************************************************
* Name: nxmutex_restorelock
*
* Description:
* This function attempts to restore the mutex.
*
* Parameters:
* mutex - mutex descriptor.
* locked - true: it's mean that the mutex is broke success
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure
*
****************************************************************************/
int nxmutex_restorelock(FAR mutex_t *mutex, bool locked)
{
return locked ? nxmutex_lock(mutex) : OK;
}
/****************************************************************************
* Name: nxrmutex_init
*
* Description:
* This function initializes the UNNAMED recursive mutex. Following a
* successful call to nxrmutex_init(), the recursive mutex may be used in
* subsequent calls to nxrmutex_lock(), nxrmutex_unlock(),
* and nxrmutex_trylock(). The recursive mutex remains usable
* until it is destroyed.
*
* Parameters:
* rmutex - Recursive mutex to be initialized
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
*
****************************************************************************/
int nxrmutex_init(FAR rmutex_t *rmutex)
{
rmutex->count = 0;
return nxmutex_init(&rmutex->mutex);
}
/****************************************************************************
* Name: nxrmutex_destroy
*
* Description:
* This function destroy the UNNAMED recursive mutex.
*
* Parameters:
* rmutex - Recursive mutex to be destroyed
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
*
****************************************************************************/
int nxrmutex_destroy(FAR rmutex_t *rmutex)
{
int ret = nxmutex_destroy(&rmutex->mutex);
if (ret >= 0)
{
rmutex->count = 0;
}
return ret;
}
/****************************************************************************
* Name: nxrmutex_is_hold
*
* Description:
* This function check whether the caller hold the recursive mutex
* referenced by 'rmutex'.
*
* Parameters:
* rmutex - Recursive mutex descriptor.
*
* Return Value:
*
****************************************************************************/
bool nxrmutex_is_hold(FAR rmutex_t *rmutex)
{
return nxmutex_is_hold(&rmutex->mutex);
}
/****************************************************************************
* Name: nxrmutex_is_locked
*
* Description:
* This function get the lock state the recursive mutex
* referenced by 'rmutex'.
*
* Parameters:
* rmutex - Recursive mutex descriptor.
*
* Return Value:
*
****************************************************************************/
bool nxrmutex_is_locked(FAR rmutex_t *rmutex)
{
return nxmutex_is_locked(&rmutex->mutex);
}
/****************************************************************************
* Name: nrxmutex_lock
*
* Description:
* This function attempts to lock the recursive mutex referenced by
* 'rmutex'.The recursive mutex can be locked multiple times in the same
* thread.
*
* Parameters:
* rmutex - Recursive mutex descriptor.
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
****************************************************************************/
int nxrmutex_lock(FAR rmutex_t *rmutex)
{
int ret = OK;
if (!nxrmutex_is_hold(rmutex))
{
ret = nxmutex_lock(&rmutex->mutex);
}
if (ret >= 0)
{
DEBUGASSERT(rmutex->count < UINT_MAX);
++rmutex->count;
}
return ret;
}
/****************************************************************************
* Name: nxrmutex_trylock
*
* Description:
* This function locks the recursive mutex if the recursive mutex is
* currently not locked or the same thread call.
* If the recursive mutex is locked and other thread call it,
* the call returns without blocking.
*
* Parameters:
* rmutex - Recursive mutex descriptor.
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
* -EINVAL - Invalid attempt to lock the recursive mutex
* -EAGAIN - The recursive mutex is not available.
*
****************************************************************************/
int nxrmutex_trylock(FAR rmutex_t *rmutex)
{
int ret = OK;
if (!nxrmutex_is_hold(rmutex))
{
ret = nxmutex_trylock(&rmutex->mutex);
}
if (ret >= 0)
{
DEBUGASSERT(rmutex->count < UINT_MAX);
++rmutex->count;
}
return ret;
}
/****************************************************************************
* Name: nxrmutex_timedlock
*
* Description:
* This function attempts to lock the mutex . If the mutex value
* is (<=) zero,then the calling task will not return until it
* successfully acquires the lock or timed out
*
* Input Parameters:
* rmutex - Rmutex object
* timeout - The time when mutex lock timed out
*
* Returned Value:
* OK The mutex successfully acquires
* EINVAL The mutex argument does not refer to a valid mutex. Or the
* thread would have blocked, and the abstime parameter specified
* a nanoseconds field value less than zero or greater than or
* equal to 1000 million.
* ETIMEDOUT The mutex could not be locked before the specified timeout
* expired.
* EDEADLK A deadlock condition was detected.
* ECANCELED May be returned if the thread is canceled while waiting.
*
****************************************************************************/
int nxrmutex_timedlock(FAR rmutex_t *rmutex, unsigned int timeout)
{
int ret = OK;
if (!nxrmutex_is_hold(rmutex))
{
ret = nxmutex_timedlock(&rmutex->mutex, timeout);
}
if (ret >= 0)
{
DEBUGASSERT(rmutex->count < UINT_MAX);
++rmutex->count;
}
return ret;
}
/****************************************************************************
* Name: nxrmutex_unlock
*
* Description:
* This function attempts to unlock the recursive mutex
* referenced by 'rmutex'.
*
* Parameters:
* rmutex - Recursive mutex descriptor.
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
* Assumptions:
* This function may be called from an interrupt handler.
*
****************************************************************************/
int nxrmutex_unlock(FAR rmutex_t *rmutex)
{
int ret = OK;
DEBUGASSERT(rmutex->count > 0);
if (--rmutex->count == 0)
{
ret = nxmutex_unlock(&rmutex->mutex);
if (ret < 0)
{
++rmutex->count;
}
}
return ret;
}
/****************************************************************************
* Name: nxrmutex_reset
*
* Description:
* This function reset lock state.
*
* Parameters:
* rmutex - rmutex descriptor.
*
****************************************************************************/
#if defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__)
void nxrmutex_reset(FAR rmutex_t *rmutex)
{
rmutex->count = 0;
nxmutex_reset(&rmutex->mutex);
}
#endif
/****************************************************************************
* Name: nrxmutex_breaklock
*
* Description:
* This function attempts to break the recursive mutex
*
* Parameters:
* rmutex - Recursive mutex descriptor.
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
****************************************************************************/
int nxrmutex_breaklock(FAR rmutex_t *rmutex, FAR unsigned int *count)
{
int ret = OK;
*count = 0;
if (nxrmutex_is_hold(rmutex))
{
*count = rmutex->count;
rmutex->count = 0;
ret = nxmutex_unlock(&rmutex->mutex);
if (ret < 0)
{
rmutex->count = *count;
}
}
return ret;
}
/****************************************************************************
* Name: nxrmutex_restorelock
*
* Description:
* This function attempts to restore the recursive mutex.
*
* Parameters:
* rmutex - Recursive mutex descriptor.
*
* Return Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
* Possible returned errors:
*
****************************************************************************/
int nxrmutex_restorelock(FAR rmutex_t *rmutex, unsigned int count)
{
int ret = OK;
if (count != 0)
{
ret = nxmutex_lock(&rmutex->mutex);
if (ret >= 0)
{
rmutex->count = count;
}
}
return ret;
}
Reference in New Issue View Git Blame Copy Permalink