Merge branch 'gspawn' into 'master'

gspawn: Optimize fd closing on AIX and BSDs

Closes #1638

See merge request GNOME/glib!574
This commit is contained in:
Philip Withnall 2019-09-26 14:01:06 +00:00
commit 6192fd4cc0

View File

@ -47,7 +47,7 @@
#include <sys/resource.h>
#endif /* HAVE_SYS_RESOURCE_H */
#ifdef __linux__
#if defined(__linux__) || defined(__DragonFly__)
#include <sys/syscall.h> /* for syscall and SYS_getdents64 */
#endif
@ -1126,7 +1126,27 @@ set_cloexec (void *data, gint fd)
return 0;
}
#ifndef HAVE_FDWALK
static gint
sane_close (gint fd)
{
gint ret;
do
ret = close (fd);
while (ret < 0 && errno == EINTR);
return ret;
}
G_GNUC_UNUSED static int
close_func (void *data, int fd)
{
if (fd >= GPOINTER_TO_INT (data))
(void) sane_close (fd);
return 0;
}
#ifdef __linux__
struct linux_dirent64
{
@ -1166,8 +1186,21 @@ filename_to_fd (const char *p)
#endif
static int
fdwalk (int (*cb)(void *data, int fd), void *data)
safe_fdwalk (int (*cb)(void *data, int fd), void *data)
{
#if 0
/* Use fdwalk function provided by the system if it is known to be
* async-signal safe.
*
* Currently there are no operating systems known to provide a safe
* implementation, so this section is not used for now.
*/
return fdwalk (cb, data);
#else
/* Fallback implementation of fdwalk. It should be async-signal safe, but it
* may be slow on non-Linux operating systems, especially on systems allowing
* very high number of open file descriptors.
*/
gint open_max;
gint fd;
gint res = 0;
@ -1200,7 +1233,7 @@ fdwalk (int (*cb)(void *data, int fd), void *data)
}
}
close (dir_fd);
sane_close (dir_fd);
return res;
}
@ -1222,18 +1255,49 @@ fdwalk (int (*cb)(void *data, int fd), void *data)
break;
return res;
}
#endif
}
static void
safe_closefrom (int lowfd)
{
#if defined(__FreeBSD__) || defined(__OpenBSD__)
/* Use closefrom function provided by the system if it is known to be
* async-signal safe.
*
* FreeBSD: closefrom is included in the list of async-signal safe functions
* found in https://man.freebsd.org/sigaction(2).
*
* OpenBSD: closefrom is not included in the list, but a direct system call
* should be safe to use.
*/
(void) closefrom (lowfd);
#elif defined(__DragonFly__)
/* It is unclear whether closefrom function included in DragonFlyBSD libc_r
* is safe to use because it calls a lot of library functions. It is also
* unclear whether libc_r itself is still being used. Therefore, we do a
* direct system call here ourselves to avoid possible issues.
*/
(void) syscall (SYS_closefrom, lowfd);
#elif defined(F_CLOSEM)
/* NetBSD and AIX have a special fcntl command which does the same thing as
* closefrom. NetBSD also includes closefrom function, which seems to be a
* simple wrapper of the fcntl command.
*/
(void) fcntl (lowfd, F_CLOSEM);
#else
(void) safe_fdwalk (close_func, GINT_TO_POINTER (lowfd));
#endif
}
static gint
sane_dup2 (gint fd1, gint fd2)
{
gint ret;
retry:
ret = dup2 (fd1, fd2);
if (ret < 0 && errno == EINTR)
goto retry;
do
ret = dup2 (fd1, fd2);
while (ret < 0 && (errno == EINTR || errno == EBUSY));
return ret;
}
@ -1243,10 +1307,9 @@ sane_open (const char *path, gint mode)
{
gint ret;
retry:
ret = open (path, mode);
if (ret < 0 && errno == EINTR)
goto retry;
do
ret = open (path, mode);
while (ret < 0 && errno == EINTR);
return ret;
}
@ -1280,21 +1343,6 @@ do_exec (gint child_err_report_fd,
if (working_directory && chdir (working_directory) < 0)
write_err_and_exit (child_err_report_fd,
CHILD_CHDIR_FAILED);
/* Close all file descriptors but stdin stdout and stderr as
* soon as we exec. Note that this includes
* child_err_report_fd, which keeps the parent from blocking
* forever on the other end of that pipe.
*/
if (close_descriptors)
{
fdwalk (set_cloexec, GINT_TO_POINTER(3));
}
else
{
/* We need to do child_err_report_fd anyway */
set_cloexec (GINT_TO_POINTER(0), child_err_report_fd);
}
/* Redirect pipes as required */
@ -1351,6 +1399,31 @@ do_exec (gint child_err_report_fd,
sane_dup2 (write_null, 2);
close_and_invalidate (&write_null);
}
/* Close all file descriptors but stdin, stdout and stderr
* before we exec. Note that this includes
* child_err_report_fd, which keeps the parent from blocking
* forever on the other end of that pipe.
*/
if (close_descriptors)
{
if (child_setup == NULL)
{
sane_dup2 (child_err_report_fd, 3);
set_cloexec (GINT_TO_POINTER (0), 3);
safe_closefrom (4);
child_err_report_fd = 3;
}
else
{
safe_fdwalk (set_cloexec, GINT_TO_POINTER (3));
}
}
else
{
/* We need to do child_err_report_fd anyway */
set_cloexec (GINT_TO_POINTER (0), child_err_report_fd);
}
/* Call user function just before we exec */
if (child_setup)