Programming Forums - View Single Post - sig_atomic_t to avoid mutex/critical sections

mynickmynick · May 5th, 2008, 8:29 AM

On linux using pthreads, if I have a 2-bytes variable x shared by pthreads used only in the following ways:
(1)

x=value;

(2) or (separately)

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if (x==value) {do something (not with x)}

(3) or (separately)

(Toggle Plain Text)

other variable (not shared) = x;

Is it correct to define it
sig_atomic_t x; (no matter if 4 or 2 bytes)
and AVOID to protect every instruction of kind (1) or (2) or (3) with pthread_mutex_lock()/trylock() before and pthread_mutex_unlock() after ?
Can I be sure there is no race condition/unpredicted event/problem?

In a few words: is it correct to speed up a software using sig_atomic_t data instead of mutexed data with the fundamental condition that data are as little as 2-4 bytes and are accessed only in the very simple way above?

Thanks

May 5th, 2008, 8:29 AM	#1
mynickmynick Newbie Join Date: May 2008 Posts: 7 Rep Power: 0	sig_atomic_t to avoid mutex/critical sections On linux using pthreads, if I have a 2-bytes variable x shared by pthreads used only in the following ways: (1) (Toggle Plain Text) x=value; x=value; (2) or (separately) (Toggle Plain Text) if (x==value) {do something (not with x)} if (x==value) {do something (not with x)} (3) or (separately) (Toggle Plain Text) other variable (not shared) = x; other variable (not shared) = x; Is it correct to define it sig_atomic_t x; (no matter if 4 or 2 bytes) and AVOID to protect every instruction of kind (1) or (2) or (3) with pthread_mutex_lock()/trylock() before and pthread_mutex_unlock() after ? Can I be sure there is no race condition/unpredicted event/problem? In a few words: is it correct to speed up a software using sig_atomic_t data instead of mutexed data with the fundamental condition that data are as little as 2-4 bytes and are accessed only in the very simple way above? Thanks