Date: Mon, 5 Oct 2009 19:17:29 +0200 From: Jilles Tjoelker <jilles@stack.nl> To: freebsd-threads@freebsd.org Subject: review request: making openat(2) a cancellation point Message-ID: <20091005171729.GA2830@stack.nl>
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While implementing a faster, cleaner and more compliant getcwd(3) using
*at functions, I noticed that openat() was not a cancellation point
(unlike open()). I think that should be fixed first, both for its own
sake and because getcwd() will need to use _openat.
I created the attached patch. It seems to work, I can still compile and
run non-threaded and threaded programs using openat() and I can cancel a
thread blocked in openat() (such as trying to open a fifo). I can also
use _openat in libc. However, I think some review is appropriate because
it all looks fairly complicated.
Because libkse and libc_r don't seem to be built, I have not updated
them.
Note that this will cause threaded 9.x binaries that use openat() to
break on 8.x. This is to be expected.
--
Jilles Tjoelker
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Index: lib/libc/include/namespace.h
===================================================================
--- lib/libc/include/namespace.h (revision 197481)
+++ lib/libc/include/namespace.h (working copy)
@@ -80,6 +80,7 @@
#define listen _listen
#define nanosleep _nanosleep
#define open _open
+#define openat _openat
#define poll _poll
#define pthread_atfork _pthread_atfork
#define pthread_attr_destroy _pthread_attr_destroy
Index: lib/libc/include/un-namespace.h
===================================================================
--- lib/libc/include/un-namespace.h (revision 197481)
+++ lib/libc/include/un-namespace.h (working copy)
@@ -61,6 +61,7 @@
#undef listen
#undef nanosleep
#undef open
+#undef openat
#undef poll
#undef pthread_atfork
#undef pthread_attr_destroy
Index: lib/libc/sys/Symbol.map
===================================================================
--- lib/libc/sys/Symbol.map (revision 197481)
+++ lib/libc/sys/Symbol.map (working copy)
@@ -769,6 +769,8 @@ FBSDprivate_1.0 {
__sys_olio_listio;
_open;
__sys_open;
+ _openat;
+ __sys_openat;
_pathconf;
__sys_pathconf;
_pipe;
Index: lib/libthr/pthread.map
===================================================================
--- lib/libthr/pthread.map (revision 197481)
+++ lib/libthr/pthread.map (working copy)
@@ -195,6 +195,7 @@ FBSDprivate_1.0 {
__msync;
__nanosleep;
__open;
+ __openat;
__poll;
__pthread_cond_timedwait;
__pthread_cond_wait;
@@ -406,3 +407,7 @@ FBSD_1.1 {
pthread_mutex_setspinloops_np;
pthread_mutex_setyieldloops_np;
};
+
+FBSD_1.2 {
+ openat;
+};
Index: lib/libthr/thread/thr_syscalls.c
===================================================================
--- lib/libthr/thread/thr_syscalls.c (revision 197481)
+++ lib/libthr/thread/thr_syscalls.c (working copy)
@@ -139,6 +139,7 @@ int __fsync(int);
int __msync(void *, size_t, int);
int __nanosleep(const struct timespec *, struct timespec *);
int __open(const char *, int,...);
+int __openat(int, const char *, int,...);
int __poll(struct pollfd *, unsigned int, int);
ssize_t __read(int, void *buf, size_t);
ssize_t __readv(int, const struct iovec *, int);
@@ -341,6 +342,33 @@ __open(const char *path, int flags,...)
return ret;
}
+__weak_reference(__openat, openat);
+
+int
+__openat(int fd, const char *path, int flags,...)
+{
+ struct pthread *curthread = _get_curthread();
+ int ret;
+ int mode = 0;
+ va_list ap;
+
+ _thr_cancel_enter(curthread);
+
+ /* Check if the file is being created: */
+ if (flags & O_CREAT) {
+ /* Get the creation mode: */
+ va_start(ap, flags);
+ mode = va_arg(ap, int);
+ va_end(ap);
+ }
+
+ ret = __sys_openat(fd, path, flags, mode);
+
+ _thr_cancel_leave(curthread);
+
+ return ret;
+}
+
__weak_reference(__poll, poll);
int
Index: lib/libthr/thread/thr_private.h
===================================================================
--- lib/libthr/thread/thr_private.h (revision 197481)
+++ lib/libthr/thread/thr_private.h (working copy)
@@ -668,6 +668,7 @@ void _pthread_cleanup_pop(int);
#ifdef _SYS_FCNTL_H_
int __sys_fcntl(int, int, ...);
int __sys_open(const char *, int, ...);
+int __sys_openat(int, const char *, int, ...);
#endif
/* #include <signal.h> */
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