diff options
Diffstat (limited to 'libc/stdio/stdio.c')
| -rw-r--r-- | libc/stdio/stdio.c | 29 |
1 files changed, 20 insertions, 9 deletions
diff --git a/libc/stdio/stdio.c b/libc/stdio/stdio.c index 2c5f3bbed..bd6a7263c 100644 --- a/libc/stdio/stdio.c +++ b/libc/stdio/stdio.c @@ -1023,31 +1023,41 @@ void _flushlbf(void) /**********************************************************************/ #ifdef L___fsetlocking -/* No (serious) reentrancy issues -- return value could be incorrect. */ -/* TODO -- fix race */ +/* NOT threadsafe!!! (I don't think glibc's is either) + * + * This interacts badly with internal locking/unlocking. If you use this routine, + * make sure the file isn't being accessed by any other threads. Typical use would + * be to change to user locking immediately after opening the stream. + */ + +link_warning(__fsetlocking, "Oddly enough, __fsetlocking() is NOT threadsafe.") int __fsetlocking(FILE *stream, int locking_mode) { +#ifdef __STDIO_THREADSAFE int old_mode; +#endif assert((FSETLOCKING_QUERY == 0) && (FSETLOCKING_INTERNAL == 1) && (FSETLOCKING_BYCALLER == 2)); assert(((unsigned int) locking_mode) <= 2); - /* Note: don't even bother locking here... */ +#ifdef __STDIO_THREADSAFE + old_mode = stream->user_locking; - old_mode = stream->user_locking; + assert(((unsigned int) old_mode) <= 1); /* Must be 0 (internal) or 1 (user). */ if (locking_mode != FSETLOCKING_QUERY) { /* In case we're not debugging, treat any unknown as a request to * set internal locking, in order to match glibc behavior. */ - stream->user_locking = ((locking_mode == FSETLOCKING_BYCALLER) - ? FSETLOCKING_BYCALLER - : FSETLOCKING_INTERNAL); + stream->user_locking = (locking_mode == FSETLOCKING_BYCALLER); } - return old_mode; + return 2 - old_mode; +#else + return FSETLOCKING_BYCALLER; /* Well, without thread support... */ +#endif } #endif @@ -1851,7 +1861,7 @@ void _stdio_term(void) * Note: Set locking mode to "by caller" to save some overhead later. */ __stdio_init_mutex(&_stdio_openlist_lock); for (ptr = _stdio_openlist ; ptr ; ptr = ptr->nextopen ) { - ptr->user_locking = FSETLOCKING_BYCALLER; + ptr->user_locking = 1; __stdio_init_mutex(&ptr->lock); } #endif /* __STDIO_THREADSAFE */ @@ -2358,6 +2368,7 @@ FILE *_stdio_fopen(const char * __restrict filename, #endif /* __STDIO_MBSTATE */ #ifdef __STDIO_THREADSAFE + stream->user_locking = 0; __stdio_init_mutex(&stream->lock); #endif /* __STDIO_THREADSAFE */ |