Re: [PATCH v3 2/3] Consolidate Linux sigprocmask implementation (BZ #22391)

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

Ping.

On 12/12/2017 15:03, Adhemerval Zanella wrote:
> Ping (with Rical suggested changes).
> 
> On 15/11/2017 15:54, Adhemerval Zanella wrote:
>> Changes from previous version:
>>
>>   - Cleanup __nptl prefix from the generic names.
>>
>> ---
>>
>> 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 (__has_internal_signal).  It is used to
>>      simplify the default sigprocmask.c implementation.
>>
>> Checked on x86_64-linux-gnu.
>>
>> 	[BZ #22391]
>> 	* 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/s390/s390-64/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/internal-signals.h
>> 	(__has_internal_signal): New function.
>> 	* sysdeps/unix/sysv/linux/sigprocmask.c (__sigprocmask):
>> 	Use __has_internal_signal and __clear_internal_signals
>> 	function.
>>
>> Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>> Signed-off-by: Zack Weinberg <zackw@panix.com>
>> Reported-by: Yury Norov <ynorov@caviumnetworks.com>
>> ---
>>  ChangeLog                                          | 17 +++++++
>>  manual/signal.texi                                 | 37 ++++++++++++++
>>  sysdeps/unix/sysv/linux/alpha/sigprocmask.c        | 58 ----------------------
>>  sysdeps/unix/sysv/linux/ia64/sigprocmask.c         | 40 ---------------
>>  sysdeps/unix/sysv/linux/internal-signals.h         |  6 +++
>>  sysdeps/unix/sysv/linux/s390/s390-64/sigprocmask.c | 38 --------------
>>  sysdeps/unix/sysv/linux/sigprocmask.c              | 23 +++------
>>  .../unix/sysv/linux/sparc/sparc64/sigprocmask.c    | 34 -------------
>>  sysdeps/unix/sysv/linux/x86_64/sigprocmask.c       | 39 ---------------
>>  9 files changed, 66 insertions(+), 226 deletions(-)
>>  delete mode 100644 sysdeps/unix/sysv/linux/alpha/sigprocmask.c
>>  delete mode 100644 sysdeps/unix/sysv/linux/ia64/sigprocmask.c
>>  delete mode 100644 sysdeps/unix/sysv/linux/s390/s390-64/sigprocmask.c
>>  delete mode 100644 sysdeps/unix/sysv/linux/sparc/sparc64/sigprocmask.c
>>  delete mode 100644 sysdeps/unix/sysv/linux/x86_64/sigprocmask.c
>>
>> diff --git a/manual/signal.texi b/manual/signal.texi
>> index 9577ff0..4f0ef59 100644
>> --- a/manual/signal.texi
>> +++ b/manual/signal.texi
>> @@ -235,6 +235,7 @@ defined.  Since the signal numbers are allocated consecutively,
>>  * Job Control Signals::         Signals used to support job control.
>>  * Operation Error Signals::     Used to report operational system errors.
>>  * Miscellaneous Signals::       Miscellaneous Signals.
>> +* Internally-Used Signals::     Signals used internally by the C library.
>>  * Signal Messages::             Printing a message describing a signal.
>>  @end menu
>>  
>> @@ -794,6 +795,26 @@ in @ref{Signaling Another Process}.
>>  The default action is to terminate the process.
>>  @end deftypevr
>>  
>> +@deftypevr Macro int SIGRTMIN
>> +@deftypevrx Macro int SIGRTMAX
>> +@standards{POSIX.1, signal.h}
>> +@cindex real-time signals
>> +The range of signal numbers @code{SIGRTMIN}, @code{SIGRTMIN+1},
>> +@dots{}, @code{SIGRTMAX} is also set aside for you to use any way you
>> +want.  In addition, these signals (and no others) are guaranteed to
>> +support @dfn{real-time} signal semantics, which unfortunately this
>> +manual does not yet document.
>> +
>> +Unlike all of the other signal number macros, @code{SIGRTMIN} and
>> +@code{SIGRTMAX} are not compile-time constants, because some operating
>> +systems make the number of real-time signals tunable on a
>> +per-installation or even per-process basis.  However, POSIX guarantees
>> +that there will be at least 8 signal numbers in this range.
>> +
>> +The default action for all signals in this range is to terminate the
>> +process.
>> +@end deftypevr
>> +
>>  @deftypevr Macro int SIGWINCH
>>  @standards{BSD, signal.h}
>>  Window size change.  This is generated on some systems (including GNU)
>> @@ -817,6 +838,22 @@ to print some status information about the system and what the process
>>  is doing.  Otherwise the default is to do nothing.
>>  @end deftypevr
>>  
>> +@node Internally-Used Signals
>> +@subsection Internally-Used Signals
>> +@cindex internally used signals
>> +
>> +On some operating systems, @theglibc{} needs to use a few signals from
>> +the ``true'' real-time range internally, to implement thread
>> +cancellation, cross-thread effective ID synchronization, POSIX timer
>> +management, etc.  @Theglibc{} adjusts @code{SIGRTMIN} and
>> +@code{SIGRTMAX} to exclude these signals, and it also takes steps to
>> +prevent application code from altering their state: @code{sigprocmask}
>> +cannot block them and @code{sigaction} cannot redefine their handlers,
>> +for instance.  Therefore, most programs do not need to know or care
>> +about these signals.  We mainly document their existence for the sake
>> +of anyone who has ever wondered why there is a gap between the
>> +highest-numbered ``normal'' signal and @code{SIGRTMIN} on Linux.
>> +
>>  @node Signal Messages
>>  @subsection Signal Messages
>>  @cindex signal messages
>> 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/internal-signals.h b/sysdeps/unix/sysv/linux/internal-signals.h
>> index e96a718..bb8234d 100644
>> --- a/sysdeps/unix/sysv/linux/internal-signals.h
>> +++ b/sysdeps/unix/sysv/linux/internal-signals.h
>> @@ -36,6 +36,12 @@
>>  #define SIGSETXID       (__SIGRTMIN + 1)
>>  
>>  
>> +static inline bool
>> +__has_internal_signal (const sigset_t *set)
>> +{
>> +  return __sigismember (set, SIGCANCEL) || __sigismember (set, SIGSETXID);
>> +}
>> +
>>  /* Return is sig is used internally.  */
>>  static inline int
>>  __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..e574b5d 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 <internal-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 (__has_internal_signal (set)))
>>      {
>>        local_newmask = *set;
>> -      __sigdelset (&local_newmask, SIGCANCEL);
>> -      __sigdelset (&local_newmask, SIGSETXID);
>> +      __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)
>>