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.Dd October 16, 2016 .Dt MTX 3 .Os .Sh NAME .Nm mtx .Nd mutex functions .Sh LIBRARY .Lb libpthread .Sh SYNOPSIS n threads.h .Ft void .Fn mtx_destroy "mtx_t *mtx" .Ft int .Fn mtx_init "mtx_t *mtx" "int type" .Ft int .Fn mtx_lock "mtx_t *mtx" .Ft int .Fn mtx_timedlock "mtx_t * restrict mtx" "const struct timespec * restrict ts" .Ft int .Fn mtx_trylock "mtx_t *mtx" .Ft int .Fn mtx_unlock "mtx_t *mtx" .Sh DESCRIPTION The .Fn mtx_destroy function releases the resources of .Fa mtx . It is not allowed to block the same .Fa mtx during the .Fn mtx_destroy call.
p The .Fn mtx_init function initialized the .Fa mtx object uniquely identificable with the .Fa type properties. The allowed values of .Fa type are as follows: l -column "mtx_plain | mtx_recursive" t Sy "Type" Ta Sy "Description" t Dv mtx_plain Ta basic mutex t Dv mtx_timed Ta mutex with timeout support t Dv mtx_plain | Dv mtx_recursive Ta basic recursive mutex t Dv mtx_timed | Dv mtx_recursive Ta recursive mutex with timeout support .El
p The underlying .Nx implementation of mutex types does not distinguish between .Dv mtx_plain and .Dv mtx_timed , however portable code must keep the distinction.
p The .Fn mtx_lock function locks the .Fa mtx object. It is required to never lock the same .Fa mtx object without the .Dv mtx_recursive property multiple times. If the .Fa mtx object is already locked by another thread, the caller of .Fa mtx_lock blocks until the lock becomes available.
p The .Fn mtx_timedlock function tries to lock the .Fa mtx object. In case of blocked resource by another thread, this call blocks for the specified timeout in the .Fa ts argument. The timeout argument is .Dv TIME_UTC based time of .Dv timespec type. It is required to never lock the same .Fa mtx object without the .Dv mtx_recursive property multiple times. In portable code, a .Fa mtx object with the .Dv mtx_recursive property must be used in such a case.
p The .Fn mtx_trylock function call attempts to lock the .Fa mtx object. This function does not block if another thread already locked the .Fa mtx object, but immediately returns indicating proper status.
p The .Fn mtx_unlock function unlocks the .Fa mtx object. This call must be preceded with a matching .Fn mtx_lock call in the same thread. .Sh RETURN VALUES The .Fn mtx_destroy function returns no value.
p The .Fn mtx_init function returns .Dv thrd_success on success or .Dv thrd_error on failure.
p The .Fn mtx_lock function returns .Dv thrd_success on success or .Dv thrd_error on failure.
p The .Fn mtx_lock function returns .Dv thrd_success on success, otherwise .Dv thrd_timedout to indicate that system time has reached or exceeded the time specified in .Dv ts , or .Dv thrd_error on failure.
p The .Fn mtx_trylock function returns .Dv thrd_success on success, otherwise .Dv thrd_timedout to indicate that .Fa mtx object is already locked, or .Dv thrd_error on failure.
p The .Fn mtx_unlock function returns .Dv thrd_success on success, otherwise .Dv thrd_timedout to indicate that .Fa mtx object is already locked, or .Dv thrd_error on failure. .Sh SEE ALSO .Xr pthread_mutex 3 , .Xr threads 3 .Sh STANDARDS The .Nm interface conforms to .St -isoC-2011 . .Sh HISTORY This interface first appeared in .Nx 9 . .Sh AUTHORS .An Kamil Rytarowski Aq Mt kamil@NetBSD.org