The __atomic_* GCC primitives were introduced in GCC 4.7, but Red Hat Enterprise Linux 6.x (for example) provides GCC 4.4. Tweak the current code to use the (most conservative) __sync_synchronize() primitive provided by those older GCC versions. Fixes https://github.com/SELinuxProject/selinux/issues/97 (Really, no __atomic or __sync operations are needed here at all, since POSIX 4.12 "Memory Synchronization" says pthread_mutex_lock() and pthread_mutex_unlock() "synchronize memory with respect to other threads"...) --- libselinux/src/label_file.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/libselinux/src/label_file.h b/libselinux/src/label_file.h index 2fa85474..47859baf 100644 --- a/libselinux/src/label_file.h +++ b/libselinux/src/label_file.h @@ -351,8 +351,14 @@ static inline int compile_regex(struct saved_data *data, struct spec *spec, * init_routine does not take a parameter, it's not possible * to use, so we generate the same effect with atomics and a * mutex */ +#ifdef __ATOMIC_RELAXED regex_compiled = __atomic_load_n(&spec->regex_compiled, __ATOMIC_ACQUIRE); +#else + /* GCC <4.7 */ + __sync_synchronize(); + regex_compiled = spec->regex_compiled; +#endif if (regex_compiled) { return 0; /* already done */ } @@ -360,8 +366,14 @@ static inline int compile_regex(struct saved_data *data, struct spec *spec, __pthread_mutex_lock(&spec->regex_lock); /* Check if another thread compiled the regex while we waited * on the mutex */ +#ifdef __ATOMIC_RELAXED regex_compiled = __atomic_load_n(&spec->regex_compiled, __ATOMIC_ACQUIRE); +#else + /* GCC <4.7 */ + __sync_synchronize(); + regex_compiled = spec->regex_compiled; +#endif if (regex_compiled) { __pthread_mutex_unlock(&spec->regex_lock); return 0; @@ -404,7 +416,13 @@ static inline int compile_regex(struct saved_data *data, struct spec *spec, } /* Done. */ +#ifdef __ATOMIC_RELAXED __atomic_store_n(&spec->regex_compiled, true, __ATOMIC_RELEASE); +#else + /* GCC <4.7 */ + spec->regex_compiled = true; + __sync_synchronize(); +#endif __pthread_mutex_unlock(&spec->regex_lock); return 0; } -- 2.13.0 _______________________________________________ Selinux mailing list Selinux@xxxxxxxxxxxxx To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx. To get help, send an email containing "help" to Selinux-request@xxxxxxxxxxxxx.
