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recursive_mutex_t struct
\file mutex.h Mutex API for non IRQ mutual exclusion between cores Mutexes are application level locks usually used protecting data structures that might be used by multiple threads of execution. Unlike critical sections, the mutex protected code is not necessarily required/expected to complete quickly, as no other system wide locks are held on account of an acquired mutex. When acquired, the mutex has an owner (see ![]()
lock_get_caller_owner_id
) which with the plain SDK is just the acquiring core, but in an RTOS it could be a task, or an IRQ handler context. Two variants of mutex are provided; ![]()
mutex_t
(and associated mutex_ functions) is a regular mutex that cannot be acquired recursively by the same owner (a deadlock will occur if you try). ![]()
recursive_mutex_t
(and associated recursive_mutex_ functions) is a recursive mutex that can be recursively obtained by the same caller, at the expense of some more overhead when acquiring and releasing. It is generally a bad idea to call blocking mutex_ or recursive_mutex_ functions from within an IRQ handler. It is valid to call mutex_try_enter or recursive_mutex_try_enter from within an IRQ handler, if the operation that would be conducted under lock can be skipped if the mutex is locked (at least by the same owner). NOTE: For backwards compatibility with version 1.2.0 of the SDK, if the define PICO_MUTEX_ENABLE_SDK120_COMPATIBILITY is set to 1, then the the regular mutex_ functions may also be used for recursive mutexes. This flag will be removed in a future version of the SDK. See ![]()
critical_section
.h for protecting access between multiple cores AND IRQ handlers recursive mutex instance
Syntax
typedef struct
{
lock_core_t core;
lock_owner_id_t owner;
uint8_t enter_count;
#if PICO_MUTEX_ENABLE_SDK120_COMPATIBILITY
bool recursive;
#endif
} recursive_mutex_t;
Fields
Field
Declared as
Description
Related Functions
Found 10 other functions taking a recursive_mutex_t
argument:
Function
Description
Release ownership of a recursive mutex
Initialise a recursive mutex structure A recursive mutex may be entered in a nested fashion by the same owner
Take ownership of a recursive mutex This function will block until the caller can be granted ownership of the mutex. On return the caller owns the mutex
Wait for mutex until a specific time Wait until the specific time to take ownership of the mutex. If the caller already has ownership of the mutex or can be granted ownership of the mutex before the timeout expires, then true will be returned and the caller will own the mutex, otherwise false will be returned and the caller will NOT own the mutex.
Attempt to take ownership of a recursive mutex If the mutex wasn't owned or was owned by the caller, this will claim the mutex and return true. Otherwise (if the mutex was already owned by another owner) this will return false and the caller will NOT own the mutex.
Wait for recursive mutex with timeout Wait for up to the specific time to take ownership of the recursive mutex. If the caller already has ownership of the mutex or can be granted ownership of the mutex before the timeout expires, then true will be returned and the caller will own the mutex, otherwise false will be returned and the caller will NOT own the mutex.
Wait for recursive mutex with timeout Wait for up to the specific time to take ownership of the recursive mutex. If the caller already has ownership of the mutex or can be granted ownership of the mutex before the timeout expires, then true will be returned and the caller will own the mutex, otherwise false will be returned and the caller will NOT own the mutex.
Test for recursive mutex initialized state