diff options
Diffstat (limited to 'perlio.c')
| -rw-r--r-- | perlio.c | 37 |
1 files changed, 24 insertions, 13 deletions
@@ -3157,19 +3157,30 @@ PerlIOStdio_close(pTHX_ PerlIO *f) saveerr = errno; invalidate = PerlIOStdio_invalidate_fileno(aTHX_ stdio); if (!invalidate) { +#ifdef USE_ITHREADS + MUTEX_LOCK(&PL_perlio_mutex); + /* Right. We need a mutex here because for a brief while we will + have the situation that fd is actually closed. Hence if a + second thread were to get into this block, its dup() would + likely return our fd as its dupfd. (after all, it is closed). + Then if we get to the dup2() first, we blat the fd back + (messing up its temporary as a side effect) only for it to + then close its dupfd (== our fd) in its close(dupfd) */ + + /* There is, of course, a race condition, that any other thread + trying to input/output/whatever on this fd will be stuffed + for the duraction of this little manoeuver. Perhaps we should + hold an IO mutex for the duration of every IO operation if + we know that invalidate doesn't work on this platform, but + that would suck, and could kill performance. + + Except that correctness trumps speed. + Advice from klortho #11912. */ +#endif dupfd = PerlLIO_dup(fd); #ifdef USE_ITHREADS - if (dupfd >= 0) { - /* Right. We need a mutex here because for a brief while we - will have the situation that fd is actually closed. - Hence if a second thread were to get into this block, - its dup() would likely return our fd as its dupfd. - (after all, it is closed). Then if we get to the dup2() - first, we blat the fd back (messing up its temporary as - a side effect) only for it to then close its dupfd - (== our fd) in its close(dupfd) */ - MUTEX_LOCK(&PL_perlio_mutex); - } else { + if (dupfd < 0) { + MUTEX_UNLOCK(&PL_perlio_mutex); /* Oh cXap. This isn't going to go well. Not sure if we can recover from here, or if closing this particular FILE * is a good idea now. */ @@ -3191,10 +3202,10 @@ PerlIOStdio_close(pTHX_ PerlIO *f) #endif if (dupfd >= 0) { PerlLIO_dup2(dupfd,fd); + PerlLIO_close(dupfd); #ifdef USE_ITHREADS - MUTEX_UNLOCK(&PL_perlio_mutex); + MUTEX_UNLOCK(&PL_perlio_mutex); #endif - PerlLIO_close(dupfd); } return result; } |