lib/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2025-07-29 11:41:21 +03:00
Code Activity

misc: Set generic pselect as ENOSYS

Browse Source 
The generic pselect implementation has the very specific race condition
that motived the creation of the pselect syscall (no atomicity in
signal mask set/reset).  Using it as generic implementation is
counterproductive  Also currently only microblaze uses it as fallback
when used on kernel prior 3.15.

This patch moves the generic implementation to a microblaze specific
one, sets the generic internal as a ENOSYS, and cleanups the Linux
generic implementation.

The microblaze implementation mimics the previous Linux generic one,
where it either uses pselect6 directly if __ASSUME_PSELECT or a
first try pselect6 then the fallback otherwise.

Checked on x86_64-linux-gnu and microblaze-linux-gnu.
This commit is contained in:
Adhemerval Zanella
2019-11-14 18:18:24 -03:00
parent 102b5b0caf
commit 8781c1301d
3 changed files with 80 additions and 76 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
misc/pselect.c
View File

@ -17,12 +17,7 @@
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <signal.h>
#include <stddef.h> /* For NULL. */
#include <sys/time.h>
#include <sys/select.h>
#include <sysdep-cancel.h>
/* Check the first NFDS descriptors each in READFDS (if not NULL) for read
readiness, in WRITEFDS (if not NULL) for write readiness, and in EXCEPTFDS
@ -34,43 +29,8 @@ int
__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
const struct timespec *timeout, const sigset_t *sigmask)
{
struct timeval tval;
int retval;
sigset_t savemask;
/* Change nanosecond number to microseconds. This might mean losing
precision and therefore the `pselect` should be available. But
for now it is hardly found. */
if (timeout != NULL)
{
/* Catch bugs which would be hidden by the TIMESPEC_TO_TIMEVAL
computations. The division by 1000 truncates values. */
if (__glibc_unlikely (timeout->tv_nsec < 0))
{
__set_errno (EINVAL);
return -1;
}
TIMESPEC_TO_TIMEVAL (&tval, timeout);
}
/* The setting and restoring of the signal mask and the select call
should be an atomic operation. This can't be done without kernel
help. */
if (sigmask != NULL)
__sigprocmask (SIG_SETMASK, sigmask, &savemask);
/* Note the pselect() is a cancellation point. But since we call
select() which itself is a cancellation point we do not have
to do anything here. */
retval = __select (nfds, readfds, writefds, exceptfds,
timeout != NULL ? &tval : NULL);
if (sigmask != NULL)
__sigprocmask (SIG_SETMASK, &savemask, NULL);
return retval;
__set_errno (ENOSYS);
return -1;
}
#ifndef __pselect
weak_alias (__pselect, pselect)
#endif
stub_warning (pselect)

73
sysdeps/unix/sysv/linux/microblaze/pselect.c Normal file
View File

@ -0,0 +1,73 @@
/* Synchronous I/O multiplexing. Linux/microblaze version.
Copyright (C) 2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <signal.h>
#include <time.h>
#include <sys/poll.h>
#include <sysdep-cancel.h>
#ifndef __ASSUME_PSELECT
# define __pselect __pselect_syscall
#endif
/* If pselect is supported, just use the Linux generic implementation. */
#include <sysdeps/unix/sysv/linux/pselect.c>
#ifndef __ASSUME_PSELECT
# undef __pselect
int
__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
const struct timespec *timeout, const sigset_t *sigmask)
{
int ret = __pselect_syscall (nfds, readfds, writefds, exceptfds, timeout,
sigmask);
if (ret >= 0 || errno != ENOSYS)
return ret;
/* The fallback uses 'select' which shows the race condition regarding
signal mask set/restore, requires two additional syscalls, and has
a worse timeout precision (microseconds instead of nanoseconds). */
struct timeval tval, *ptval = NULL;
if (timeout != NULL)
{
if (! valid_nanoseconds (timeout->tv_nsec))
{
__set_errno (EINVAL);
return -1;
}
TIMESPEC_TO_TIMEVAL (&tval, timeout);
ptval = &tval;
}
sigset_t savemask;
if (sigmask != NULL)
__sigprocmask (SIG_SETMASK, sigmask, &savemask);
/* select itself is a cancellation entrypoint. */
ret = __select (nfds, readfds, writefds, exceptfds, ptval);
if (sigmask != NULL)
__sigprocmask (SIG_SETMASK, &savemask, NULL);
return ret;
}
weak_alias (__pselect, pselect)
#endif

37
sysdeps/unix/sysv/linux/pselect.c
View File

@ -16,23 +16,9 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <signal.h>
#include <time.h>
#include <sys/poll.h>
#include <kernel-features.h>
#include <sys/select.h>
#include <sysdep-cancel.h>
#ifdef __NR_pselect6
# ifndef __ASSUME_PSELECT
static int __generic_pselect (int nfds, fd_set *readfds, fd_set *writefds,
fd_set *exceptfds,
const struct timespec *timeout,
const sigset_t *sigmask);
# endif
int
__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
const struct timespec *timeout, const sigset_t *sigmask)
@ -59,24 +45,9 @@ __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
data.ss = (__syscall_ulong_t) (uintptr_t) sigmask;
data.ss_len = _NSIG / 8;
int result = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds,
timeout, &data);
# ifndef __ASSUME_PSELECT
if (result == -1 && errno == ENOSYS)
result = __generic_pselect (nfds, readfds, writefds, exceptfds, timeout,
sigmask);
# endif
return result;
return SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds,
timeout, &data);
}
#ifndef __pselect
weak_alias (__pselect, pselect)
# ifndef __ASSUME_PSELECT
# define __pselect static __generic_pselect
# endif
#endif
#ifndef __ASSUME_PSELECT
# include <misc/pselect.c>
#endif