Mutexes

Collaboration diagram for Mutexes:

Functions
err_t	sys_mutex_new (sys_mutex_t *mutex)
void	sys_mutex_lock (sys_mutex_t *mutex)
void	sys_mutex_unlock (sys_mutex_t *mutex)
void	sys_mutex_free (sys_mutex_t *mutex)
int	sys_mutex_valid (sys_mutex_t *mutex)
void	sys_mutex_set_invalid (sys_mutex_t *mutex)

Detailed Description

Mutexes are recommended to correctly handle priority inversion, especially if you use LWIP_CORE_LOCKING .

Function Documentation

sys_mutex_free()

void sys_mutex_free

(

sys_mutex_t *

mutex

)

Deallocates a mutex.

Parameters

mutex

the mutex to delete

Definition at line 157 of file sys_arch.c.

{
  /* parameter check */
  LWIP_ASSERT("mutex != NULL", mutex != NULL);
  LWIP_ASSERT("*mutex >= 1", *mutex >= 1);
  *mutex = 0;
}

sys_mutex_lock()

void sys_mutex_lock

(

sys_mutex_t *

mutex

)

Blocks the thread until the mutex can be grabbed.

Parameters

mutex

the mutex to lock

Definition at line 173 of file sys_arch.c.

{
  /* nothing to do, no multithreading supported */
  LWIP_ASSERT("mutex != NULL", mutex != NULL);
  /* check that the mutext is valid and unlocked (no nested locking) */
  LWIP_ASSERT("*mutex >= 1", *mutex == 1);
  /* we count up just to check the correct pairing of lock/unlock */
  (*mutex)++;
  LWIP_ASSERT("*mutex >= 1", *mutex >= 1);
}

Referenced by mem_malloc().

sys_mutex_new()

err_t sys_mutex_new

(

sys_mutex_t *

mutex

)

Create a new mutex. Note that mutexes are expected to not be taken recursively by the lwIP code, so both implementation types (recursive or non-recursive) should work. The mutex is allocated to the memory that 'mutex' points to (which can be both a pointer or the actual OS structure). If the mutex has been created, ERR_OK should be returned. Returning any other error will provide a hint what went wrong, but except for assertions, no real error handling is implemented.

Parameters

mutex

pointer to the mutex to create

Returns

ERR_OK if successful, another err_t otherwise

Definition at line 149 of file sys_arch.c.

{
  LWIP_ASSERT("mutex != NULL", mutex != NULL);
  *mutex = 1; /* 1 allocated */
  return ERR_OK;
}

Referenced by mem_init(), and tcpip_init().

sys_mutex_set_invalid()

void sys_mutex_set_invalid

(

sys_mutex_t *

mutex

)

Invalidate a mutex so that sys_mutex_valid() returns 0. ATTENTION: This does NOT mean that the mutex shall be deallocated: sys_mutex_free() is always called before calling this function! This may also be a define, in which case the function is not prototyped.

Definition at line 166 of file sys_arch.c.

{
  LWIP_ASSERT("mutex != NULL", mutex != NULL);
  *mutex = 0;
}

sys_mutex_unlock()

void sys_mutex_unlock

(

sys_mutex_t *

mutex

)

Releases the mutex previously locked through 'sys_mutex_lock()'.

Parameters

mutex

the mutex to unlock

Definition at line 185 of file sys_arch.c.

{
  /* nothing to do, no multithreading supported */
  LWIP_ASSERT("mutex != NULL", mutex != NULL);
  LWIP_ASSERT("*mutex >= 1", *mutex >= 1);
  /* we count down just to check the correct pairing of lock/unlock */
  (*mutex)--;
  LWIP_ASSERT("*mutex >= 1", *mutex >= 1);
}

Referenced by mem_malloc().

sys_mutex_valid()

int sys_mutex_valid

(

sys_mutex_t *

mutex

)

Returns 1 if the mutes is valid, 0 if it is not valid. When using pointers, a simple way is to check the pointer for != NULL. When directly using OS structures, implementing this may be more complex. This may also be a define, in which case the function is not prototyped.