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Re: [PATCH 2/3] Consolidate Linux sigprocmask() implementation
On 16/10/2017 02:34, Yury Norov wrote:
> ia64, s390-64, sparc64, x86_64 and alpha ports has their own
> implementations of sigprocmask(). They all but alpha do exactly
> what generic sigprocmask() except the check and clear SIGCANCEL
> and SIGSETXID flags.
>
> In this patch, the NEED_CLEAR_SIGCANCEL_SIGSETXID option is
> introduced and disabled for that ports which allows to swith
> them to generic implementation.
Although the manual do not state the Linux implementation detail I think
all supported Linux architecture should have the same semantic regarding
SIGCANCEL and SIGSETXID. GLIBC on Linux requires both signal to proper
implement both pthread cancellation and set*id function and having
different semanticsis troublesome (a conformant program on a architecture
that does not filter out the signals might inadvertently disable pthread
asynchronous cancellation, set*id synchronization or posix timers).
Also, sigfillset removes SIGCANCEL and SIGSETXID as expected, but
sigaddset and sigdelset does not handle none of internal signals. I also
think we should ignore internal nptl signals on sigaddset and sigdelset.
And for this specific case I don't see adding compat symbols to keep
the old semantic for the related architectures the best approach. There
is a canonical way to actually disable pthread cancellation and masking
SIGSETXID would make set*id non POSIX conformant.
What about the following?
---
This patch consolidates the sigprocmask Linux syscall implementation on
sysdeps/unix/sysv/linux/sigprocmask.c. The changes are:
1. For ia64, s390-64, sparc64, and x86_64 the default semantic for
filter out SIGCANCEL and SIGSETXID is used. Also the Linux pthread
semantic is documented in the signal chapter.
2. A new internal function to check for NPTL internal signals within a
signal set is added (__nptl_has_internal_signal). It is used to
simplify the default sigprocmask.c implementation.
Checked on x86_64-linux-gnu.
* manual/signal.texi: Add a note about internal pthread signals
on Linux.
* sysdeps/unix/sysv/linux/alpha/sigprocmask.c: Remove file.
* sysdeps/unix/sysv/linux/ia64/sigprocmask.c: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/sigprocmask.c: Likewise.
* sysdeps/unix/sysv/linux/x86_64/sigprocmask.c: Likewise.
* sysdeps/unix/sysv/linux/nptl-signals.h
(__nptl_has_internal_signal): New function.
* sysdeps/unix/sysv/linux/sigprocmask.c (__sigprocmask):
Use __nptl_has_internal_signal and __nptl_clear_internal_signals
function.
Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
---
diff --git a/manual/signal.texi b/manual/signal.texi
index 9577ff0..46696af 100644
--- a/manual/signal.texi
+++ b/manual/signal.texi
@@ -2461,6 +2461,11 @@ well. (In addition, it's not wise to put into your program an
assumption that the system has no signals aside from the ones you know
about.)
+On Linux pthreads internally uses some signals to implement asynchronous
+cancellation, effective ID synchronization for POSIX conformance, and
+posix timer management. These signals are filtered out on signal set
+function manipulation.
+
@deftypefun int sigemptyset (sigset_t *@var{set})
@standards{POSIX.1, signal.h}
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
diff --git a/sysdeps/unix/sysv/linux/alpha/sigprocmask.c b/sysdeps/unix/sysv/linux/alpha/sigprocmask.c
deleted file mode 100644
index ebec70c..0000000
--- a/sysdeps/unix/sysv/linux/alpha/sigprocmask.c
+++ /dev/null
@@ -1,58 +0,0 @@
-/* Copyright (C) 1993-2017 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- Contributed by David Mosberger (davidm@azstarnet.com).
-
- 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
- <http://www.gnu.org/licenses/>. */
-
-#include <errno.h>
-#include <sysdep.h>
-#include <signal.h>
-
-/* When there is kernel support for more than 64 signals, we'll have to
- switch to a new system call convention here. */
-
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
- unsigned long int setval;
- long result;
-
- if (set)
- setval = set->__val[0];
- else
- {
- setval = 0;
- how = SIG_BLOCK; /* ensure blocked mask doesn't get changed */
- }
-
- result = INLINE_SYSCALL (osf_sigprocmask, 2, how, setval);
- if (result == -1)
- /* If there are ever more than 63 signals, we need to recode this
- in assembler since we wouldn't be able to distinguish a mask of
- all 1s from -1, but for now, we're doing just fine... */
- return result;
-
- if (oset)
- {
- oset->__val[0] = result;
- result = _SIGSET_NWORDS;
- while (--result > 0)
- oset->__val[result] = 0;
- }
- return 0;
-}
-
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask);
diff --git a/sysdeps/unix/sysv/linux/ia64/sigprocmask.c b/sysdeps/unix/sysv/linux/ia64/sigprocmask.c
deleted file mode 100644
index 920c5fd..0000000
--- a/sysdeps/unix/sysv/linux/ia64/sigprocmask.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/* Copyright (C) 1997-2017 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- Linux/IA64 specific sigprocmask
- Written by Jes Sorensen, <Jes.Sorensen@cern.ch>, April 1999.
-
- 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
- <http://www.gnu.org/licenses/>. */
-
-/* Linux/ia64 only has rt signals, thus we do not even want to try falling
- back to the old style signals as the default Linux handler does. */
-
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/* Get and/or change the set of blocked signals. */
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
-
- /* XXX The size argument hopefully will have to be changed to the
- real size of the user-level sigset_t. */
- return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
-}
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask)
diff --git a/sysdeps/unix/sysv/linux/nptl-signals.h b/sysdeps/unix/sysv/linux/nptl-signals.h
index f30c597..6afd3fe 100644
--- a/sysdeps/unix/sysv/linux/nptl-signals.h
+++ b/sysdeps/unix/sysv/linux/nptl-signals.h
@@ -33,6 +33,12 @@
#define SIGSETXID (__SIGRTMIN + 1)
+static inline bool
+__nptl_has_internal_signal (const sigset_t *set)
+{
+ return __sigismember (set, SIGCANCEL) || __sigismember (set, SIGSETXID);
+}
+
/* Return is sig is used internally. */
static inline int
__nptl_is_internal_signal (int sig)
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/sigprocmask.c b/sysdeps/unix/sysv/linux/s390/s390-64/sigprocmask.c
deleted file mode 100644
index a8010e7..0000000
--- a/sysdeps/unix/sysv/linux/s390/s390-64/sigprocmask.c
+++ /dev/null
@@ -1,38 +0,0 @@
-/* Copyright (C) 2001-2017 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
- <http://www.gnu.org/licenses/>. */
-
-/* 64 bit Linux for S/390 only has rt signals, thus we do not even want to try
- falling back to the old style signals as the default Linux handler does. */
-
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/* Get and/or change the set of blocked signals. */
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
-
- /* XXX The size argument hopefully will have to be changed to the
- real size of the user-level sigset_t. */
- return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
-}
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask)
diff --git a/sysdeps/unix/sysv/linux/sigprocmask.c b/sysdeps/unix/sysv/linux/sigprocmask.c
index e776563..d14fc5c 100644
--- a/sysdeps/unix/sysv/linux/sigprocmask.c
+++ b/sysdeps/unix/sysv/linux/sigprocmask.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 1997-2017 Free Software Foundation, Inc.
+/* Get and/or change the set of blocked signals. Linux version.
+ Copyright (C) 1997-2017 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
@@ -17,34 +18,22 @@
#include <errno.h>
#include <signal.h>
-#include <string.h> /* Needed for string function builtin redirection. */
-#include <unistd.h>
+#include <nptl-signals.h>
-#include <sysdep.h>
-#include <sys/syscall.h>
-#include <nptl/pthreadP.h> /* SIGCANCEL, SIGSETXID */
-
-
-/* Get and/or change the set of blocked signals. */
int
__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
{
sigset_t local_newmask;
- /* The only thing we have to make sure here is that SIGCANCEL and
- SIGSETXID are not blocked. */
- if (set != NULL
- && (__builtin_expect (__sigismember (set, SIGCANCEL), 0)
- || __builtin_expect (__sigismember (set, SIGSETXID), 0)))
+ if (set != NULL && __glibc_unlikely (__nptl_has_internal_signal (set)))
{
local_newmask = *set;
- __sigdelset (&local_newmask, SIGCANCEL);
- __sigdelset (&local_newmask, SIGSETXID);
+ __nptl_clear_internal_signals (&local_newmask);
set = &local_newmask;
}
- return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
+ return INLINE_SYSCALL_CALL (rt_sigprocmask, how, set, oset, _NSIG / 8);
}
libc_hidden_def (__sigprocmask)
weak_alias (__sigprocmask, sigprocmask)
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/sigprocmask.c b/sysdeps/unix/sysv/linux/sparc/sparc64/sigprocmask.c
deleted file mode 100644
index ef7d7fe..0000000
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/sigprocmask.c
+++ /dev/null
@@ -1,34 +0,0 @@
-/* Copyright (C) 1997-2017 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
- <http://www.gnu.org/licenses/>. */
-
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/* Get and/or change the set of blocked signals. */
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
- /* XXX The size argument hopefully will have to be changed to the
- real size of the user-level sigset_t. */
- return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
-}
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask)
diff --git a/sysdeps/unix/sysv/linux/x86_64/sigprocmask.c b/sysdeps/unix/sysv/linux/x86_64/sigprocmask.c
deleted file mode 100644
index 1610ddf..0000000
--- a/sysdeps/unix/sysv/linux/x86_64/sigprocmask.c
+++ /dev/null
@@ -1,39 +0,0 @@
-/* Copyright (C) 1997-2017 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- Written by Jes Sorensen, <Jes.Sorensen@cern.ch>, April 1999.
-
- 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
- <http://www.gnu.org/licenses/>. */
-
-/* Linux/x86_64 only has rt signals, thus we do not even want to try falling
- back to the old style signals as the default Linux handler does. */
-
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/* Get and/or change the set of blocked signals. */
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
-
- /* XXX The size argument hopefully will have to be changed to the
- real size of the user-level sigset_t. */
- return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
-}
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask)