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| author | Rich Felker <dalias@aerifal.cx> | 2011-07-30 08:02:14 -0400 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2011-07-30 08:02:14 -0400 |
| commit | dba68bf98fc708cea4c478278c889fc7ad802b00 (patch) | |
| tree | b90a55aaa51c72475cdb69efca7b9ddd37e50b2e /src/internal/stdio_impl.h | |
| parent | 7683fceedebd98dda19b1a379b92406b64ce7f92 (diff) | |
| download | musl-dba68bf98fc708cea4c478278c889fc7ad802b00.tar.gz musl-dba68bf98fc708cea4c478278c889fc7ad802b00.tar.xz musl-dba68bf98fc708cea4c478278c889fc7ad802b00.zip | |
add proper fuxed-based locking for stdio
previously, stdio used spinlocks, which would be unacceptable if we ever add support for thread priorities, and which yielded pathologically bad performance if an application attempted to use flockfile on a key file as a major/primary locking mechanism. i had held off on making this change for fear that it would hurt performance in the non-threaded case, but actually support for recursive locking had already inflicted that cost. by having the internal locking functions store a flag indicating whether they need to perform unlocking, rather than using the actual recursive lock counter, i was able to combine the conditionals at unlock time, eliminating any additional cost, and also avoid a nasty corner case where a huge number of calls to ftrylockfile could cause deadlock later at the point of internal locking. this commit also fixes some issues with usage of pthread_self conflicting with __attribute__((const)) which resulted in crashes with some compiler versions/optimizations, mainly in flockfile prior to pthread_create.
Diffstat (limited to 'src/internal/stdio_impl.h')
| -rw-r--r-- | src/internal/stdio_impl.h | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/src/internal/stdio_impl.h b/src/internal/stdio_impl.h index 76b58be9..c5f45eb1 100644 --- a/src/internal/stdio_impl.h +++ b/src/internal/stdio_impl.h @@ -24,8 +24,8 @@ #define UNGET 8 -#define FLOCK(f) ((libc.threads_minus_1 && (f)->lock>=0) ? (__lockfile((f)),0) : 0) -#define FUNLOCK(f) ((f)->lockcount && (--(f)->lockcount || ((f)->lock=0))) +#define FLOCK(f) int __need_unlock = ((f)->lock>=0 ? __lockfile((f)) : 0) +#define FUNLOCK(f) if (__need_unlock) __unlockfile((f)); else #define F_PERM 1 #define F_NORD 4 @@ -49,12 +49,12 @@ struct __FILE_s { FILE *prev, *next; int fd; int pipe_pid; - long dummy2; + long lockcount; short dummy3; signed char mode; signed char lbf; int lock; - int lockcount; + int waiters; void *cookie; off_t off; int (*flush)(FILE *); @@ -86,7 +86,6 @@ FILE *__fdopen(int, const char *); #define OFLLOCK() LOCK(&libc.ofl_lock) #define OFLUNLOCK() UNLOCK(&libc.ofl_lock) -#define ofl_head (libc.ofl_head) #define feof(f) ((f)->flags & F_EOF) #define ferror(f) ((f)->flags & F_ERR) |