diff options
| 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 | |
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) |