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Jeremie Koenig 653d74f12a hurd: Global signal disposition
This adds _hurd_sigstate_set_global_rcv used by libpthread to enable
POSIX-confirming behavior of signals on a per-thread basis.

This also provides a sigstate destructor _hurd_sigstate_delete, and a
global process signal state, which needs to be locked and check when
global disposition is enabled, thus the addition of _hurd_sigstate_lock
_hurd_sigstate_actions _hurd_sigstate_pending _hurd_sigstate_unlock helpers.

This also updates all the glibc code accordingly.

This also drops support for get_int(INIT_SIGMASK), which did not make sense
any more since we do not have a single signal thread any more.

During fork/spawn, this also reinitializes the child global sigstate's
lock. That cures an issue that would very rarely cause a deadlock in the
child in fork, tries to unlock ss' critical section lock at the end of
fork.  This will typically (always?) be observed in /bin/sh, which is not
surprising as that is the foremost caller of fork.

To reproduce an intermediate state, add an endless loop if
_hurd_global_sigstate is locked after __proc_dostop (cast through
volatile); that is, while still being in the fork's parent process.

When that triggers (use the libtool testsuite), the signal thread has
already locked ss (which is _hurd_global_sigstate), and is stuck at
hurdsig.c:685 in post_signal, trying to lock _hurd_siglock (which the
main thread already has locked and keeps locked until after
__task_create).  This is the case that ss->thread == MACH_PORT_NULL, that
is, a global signal.  In the main thread, between __proc_dostop and
__task_create is the __thread_abort call on the signal thread which would
abort any current kernel operation (but leave ss locked).  Later in fork,
in the parent, when _hurd_siglock is unlocked in fork, the parent's
signal thread can proceed and will unlock eventually the global sigstate.
In the client, _hurd_siglock will likewise be unlocked, but the global
sigstate never will be, as the client's signal thread has been configured
to restart execution from _hurd_msgport_receive.  Thus, when the child
tries to unlock ss' critical section lock at the end of fork, it will
first lock the global sigstate, will spin trying to lock it, which can
never be successful, and we get our deadlock.

Options seem to be:

  * Move the locking of _hurd_siglock earlier in post_signal -- but that
    may generally impact performance, if this locking isn't generally
    needed anyway?

    On the other hand, would it actually make sense to wait here until we
    are not any longer in a critical section (which is meant to disable
    signal delivery anyway (but not for preempted signals?))?

  * Clear the global sigstate in the fork's child with the rationale that
    we're anyway restarting the signal thread from a clean state.  This
    has now been implemented.

Why has this problem not been observed before Jérémie's patches?  (Or has
it?  Perhaps even more rarely?)  In _S_msg_sig_post, the signal is now
posted to a *global receiver thread*, whereas previously it was posted to
the *designated signal-receiving thread*.  The latter one was in a
critical section in fork, so didn't try to handle the signal until after
leaving the critical section?  (Not completely analyzed and verified.)

Another question is what the signal is that is being received
during/around the time __proc_dostop executes.
2019-12-29 18:32:49 +01:00
argp Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
assert Fix failure when CFLAGS contains -DNDEBUG (Bug 25251) 2019-12-10 12:22:42 -05:00
benchtests Add new script for plotting string benchmark JSON output 2019-11-13 14:18:52 +00:00
bits Do not redirect calls to __GI_* symbols, when redirecting to *ieee128 2019-12-27 15:02:10 -03:00
catgets Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
ChangeLog.old Undo accidental commit to ChangeLog.19. 2019-10-18 16:09:10 -04:00
conform sysvipc: Set ipc_perm mode as mode_t (BZ#18231) 2019-10-10 17:33:27 -03:00
crypt Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
csu Introduce link_map_audit_state accessor function 2019-11-15 13:03:40 +01:00
ctype Split up endian.h to minimize exposure of BYTE_ORDER. 2019-10-01 14:54:46 -07:00
debug Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
dirent Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
dlfcn dlfcn: Remove remnants of caller sensitivity from dlinfo 2019-10-16 18:21:30 +02:00
elf Fix test isolation for elf/tst-ifunc-fault-lazy, elf/tst-ifunc-fault-bindnow 2019-12-19 16:06:50 +01:00
gmon Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
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htl Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
hurd hurd: Global signal disposition 2019-12-29 18:32:49 +01:00
iconv Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
iconvdata Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
include Do not redirect calls to __GI_* symbols, when redirecting to *ieee128 2019-12-27 15:02:10 -03:00
inet Change most internal uses of __gettimeofday to __clock_gettime. 2019-10-30 17:04:10 -03:00
intl Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
io hurd: Fix ld.so __access override from libc 2019-12-01 21:05:56 +00:00
libio Remove __waitpid_nocancel 2019-12-19 16:11:09 -03:00
locale locale: Greek -> ASCII transliteration table [BZ #12031] 2019-11-26 12:23:09 +01:00
localedata mnw_MM, my_MM, and shn_MM locales: Do not use %Op 2019-12-23 23:49:22 +01:00
login login: Use pread64 in utmp implementation 2019-11-12 20:13:35 +01:00
mach hurd: make strerror(0) coherent with other ports 2019-12-01 16:36:43 +00:00
malloc Correct range checking in mallopt/mxfast/tcache [BZ #25194] 2019-12-05 16:46:37 -05:00
manual aarch64: Add Huawei Kunpeng to tunable cpu list 2019-12-19 16:31:04 -03:00
math math: enhance the endloop condition of function handle_input_flag 2019-11-07 00:26:54 +00:00
mathvec Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
misc ldbl-128ibm-compat: Add *cvt functions 2019-12-23 16:32:20 -03:00
nis Change most internal uses of __gettimeofday to __clock_gettime. 2019-10-30 17:04:10 -03:00
nptl nptl: Move waitpid implementation to libc 2019-12-19 16:11:09 -03:00
nptl_db slotinfo in struct dtv_slotinfo_list should be flexible array [BZ #25097] 2019-11-12 13:54:30 +01:00
nscd Change most internal uses of time to __clock_gettime. 2019-10-30 17:11:10 -03:00
nss Comment out initgroups from example nsswitch.conf (Bug 25146) 2019-10-29 13:08:24 -04:00
po Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
posix Add exception-based flags for wait4 2019-12-20 09:59:11 -03:00
pwd Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
resolv resolv: Implement trust-ad option for /etc/resolv.conf [BZ #20358] 2019-11-27 20:54:37 +01:00
resource Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
rt Set the expects flags to clock_nanosleep 2019-09-25 16:28:45 -07:00
scripts build-many-glibcs.py: Do not build C++ PCHs by default 2019-12-18 08:47:45 +01:00
setjmp Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
shadow Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
signal Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
socket Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
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stdio-common Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
stdlib hurd: Fix local PLT 2019-12-13 11:11:54 +01:00
string <string.h>: Define __CORRECT_ISO_CPP_STRING_H_PROTO for Clang [BZ #25232] 2019-12-05 16:50:00 +01:00
sunrpc Change most internal uses of __gettimeofday to __clock_gettime. 2019-10-30 17:04:10 -03:00
support resolv: Implement trust-ad option for /etc/resolv.conf [BZ #20358] 2019-11-27 20:54:37 +01:00
sysdeps hurd: Global signal disposition 2019-12-29 18:32:49 +01:00
sysvipc Remove libc_hidden_def from __semtimedop stub 2019-10-17 21:36:34 +02:00
termios Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
time Declare asctime_r, ctime_r, gmtime_r, localtime_r for C2X. 2019-11-11 15:04:48 +00:00
timezone Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
wcsmbs Use DEPRECATED_SCANF macro for remaining C99-compliant scanf functions 2019-11-22 15:29:21 -03:00
wctype Split up endian.h to minimize exposure of BYTE_ORDER. 2019-10-01 14:54:46 -07:00
.gitattributes Assume __NR_openat is always defined 2016-03-23 23:35:08 +01:00
.gitignore Add *.pyc to .gitignore 2015-05-18 15:26:26 +05:30
abi-tags Remove the bulk of the NaCl port. 2017-05-20 08:09:10 -04:00
aclocal.m4 LIBC_SLIBDIR_RTLDDIR: substitute arguments in single quotes 2018-01-25 17:20:28 +01:00
config.h.in sparc: Assume GOTDATA support in the toolchain 2019-10-09 19:15:33 +02:00
config.make.in Make --bindir effective 2019-05-14 11:04:33 -03:00
configure x86: Assume --enable-cet if GCC defaults to CET [BZ #25225] 2019-12-03 18:48:18 +01:00
configure.ac x86: Assume --enable-cet if GCC defaults to CET [BZ #25225] 2019-12-03 18:48:18 +01:00
COPYING Update to latest versions of GPL-2.0 and LGPL-2.1 2013-09-09 12:52:48 +10:00
COPYING.LIB Update to latest versions of GPL-2.0 and LGPL-2.1 2013-09-09 12:52:48 +10:00
extra-lib.mk Rename cppflags-iterator.mk to libof-iterator.mk, remove extra-modules.mk. 2017-05-09 07:06:29 -04:00
gen-locales.mk Improve gen-locales.mk and gen-locale.sh to make test files with @ options work 2018-02-27 17:01:57 +01:00
INSTALL Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
libc-abis libc-abis: Define ABSOLUTE ABI [BZ #19818][BZ #23307] 2018-07-05 18:06:43 +01:00
libof-iterator.mk Rename cppflags-iterator.mk to libof-iterator.mk, remove extra-modules.mk. 2017-05-09 07:06:29 -04:00
LICENSES Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
MAINTAINERS Add MAINTAINERS 2017-05-11 13:38:30 -04:00
Makeconfig Expand $(as-needed) and $(no-as-needed) throughout the build system 2019-12-03 21:37:50 +01:00
Makefile Do not use ld.so to open statically linked programs in debugglibc.sh 2019-12-04 09:17:06 -03:00
Makefile.help Add run-one-test convenience target and makefile help text 2019-10-18 15:46:04 -04:00
Makefile.in New make target to only build benchmark binaries 2016-04-20 10:23:28 +05:30
Makerules Expand $(as-needed) and $(no-as-needed) throughout the build system 2019-12-03 21:37:50 +01:00
NEWS Lazy binding failures during dlopen/dlclose must be fatal [BZ #24304] 2019-11-27 20:55:35 +01:00
o-iterator.mk Fri Mar 17 12:58:37 1995 Roland McGrath <roland@churchy.gnu.ai.mit.edu> 1995-03-17 18:42:51 +00:00
README Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
Rules Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
shlib-versions Extend NSS test suite 2017-07-17 15:52:44 -04:00
test-skeleton.c Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
version.h Open master for 2.31 development. 2019-08-01 00:41:53 -04:00

This directory contains the sources of the GNU C Library.
See the file "version.h" for what release version you have.

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