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misc: Set generic pselect as ENOSYS

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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
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44
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);
__set_errno (ENOSYS);
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;
}
#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

35
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,
return 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;
}
#ifndef __pselect
weak_alias (__pselect, pselect)
# ifndef __ASSUME_PSELECT
# define __pselect static __generic_pselect
# endif
#endif
#ifndef __ASSUME_PSELECT
# include <misc/pselect.c>
#endif