Fix the handle locking in stdio
Fix the handle locking in stdio to use flockfile/funlockfile
internally when and where required. Macros in <stdio.h> are updated
to automatically call the underlying functions when the process is
threaded to obtain the necessary locking. A private mutex is added
to protect __sglue, the internal list of FILE handles, and another
to protect the one-time initialization. Some routines in libc that
use getc() change to use getc_unlocked() as they're either protected
by their own lock or aren't thread-safe routines anyway.
Based on OpenBSD change by guenther@openbsd.org
http://www.mail-archive.com/source-changes@cvs.openbsd.org/msg01015.html
Bug: 3446659
Change-Id: Ie82116e358c541718d6709ec45ca6796be5a007b
diff --git a/libc/stdio/refill.c b/libc/stdio/refill.c
index 74b378e..7cb6b78 100644
--- a/libc/stdio/refill.c
+++ b/libc/stdio/refill.c
@@ -39,9 +39,8 @@
static int
lflush(FILE *fp)
{
-
if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
- return (__sflush(fp));
+ return (__sflush_locked(fp)); /* ignored... */
return (0);
}
@@ -103,8 +102,16 @@
* flush all line buffered output files, per the ANSI C
* standard.
*/
- if (fp->_flags & (__SLBF|__SNBF))
+ if (fp->_flags & (__SLBF|__SNBF)) {
+ /* Ignore this file in _fwalk to avoid potential deadlock. */
+ fp->_flags |= __SIGN;
(void) _fwalk(lflush);
+ fp->_flags &= ~__SIGN;
+
+ /* Now flush this file without locking it. */
+ if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
+ __sflush(fp);
+ }
fp->_p = fp->_bf._base;
fp->_r = (*fp->_read)(fp->_cookie, (char *)fp->_p, fp->_bf._size);
fp->_flags &= ~__SMOD; /* buffer contents are again pristine */