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darwin: work around concurrent write() kernel bug

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Simultaneously writing from multiple threads to the same file descriptor is not
safe on OS X. We already serialized all pwrite() system calls, apply the same
workaround to the write() system call.

Fixes a node.js test, test/simple/test-fs-sir-writes-alot.js, that was failing
because parts of the output file got filled with nul bytes.
This commit is contained in:
Ben Noordhuis 2012-10-10 02:09:37 +02:00
parent 4affbe70b6
commit cb03e3bd26
1 changed files with 19 additions and 20 deletions
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39
src/unix/fs.c
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@ -133,24 +133,6 @@ static ssize_t uv__fs_futime(uv_fs_t* req) {
}
static ssize_t uv__fs_pwrite(uv_fs_t* req) {
#if defined(__APPLE__)
/* Serialize writes on OS X, concurrent pwrite() calls result in data loss.
* We can't use a per-file descriptor lock, the descriptor may be a dup().
*/
static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
ssize_t r;
pthread_mutex_lock(&lock);
r = pwrite(req->file, req->buf, req->len, req->off);
pthread_mutex_unlock(&lock);
return r;
#else
return pwrite(req->file, req->buf, req->len, req->off);
#endif
}
static ssize_t uv__fs_read(uv_fs_t* req) {
if (req->off < 0)
return read(req->file, req->buf, req->len);
@ -447,10 +429,27 @@ static ssize_t uv__fs_utime(uv_fs_t* req) {
static ssize_t uv__fs_write(uv_fs_t* req) {
ssize_t r;
/* Serialize writes on OS X, concurrent write() and pwrite() calls result in
* data loss. We can't use a per-file descriptor lock, the descriptor may be
* a dup().
*/
#if defined(__APPLE__)
static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_lock(&lock);
#endif
if (req->off < 0)
return write(req->file, req->buf, req->len);
r = write(req->file, req->buf, req->len);
else
return uv__fs_pwrite(req);
r = pwrite(req->file, req->buf, req->len, req->off);
#if defined(__APPLE__)
pthread_mutex_unlock(&lock);
#endif
return r;
}