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authorJörg Frings-Fürst <debian@jff.email>2022-01-08 11:51:07 +0100
committerJörg Frings-Fürst <debian@jff.email>2022-01-08 11:51:07 +0100
commitbe8efac78d067c138ad8dda03df4336e73f94887 (patch)
tree5f5254a628ba0ef72065b93d949d1c985742ea8e /gnulib-m4/pthread_rwlock_rdlock.m4
parent7b65dbd4ebade81d504cfe5e681292a58ad1fdf0 (diff)
New upstream version 1.0upstream/1.0
Diffstat (limited to 'gnulib-m4/pthread_rwlock_rdlock.m4')
-rw-r--r--gnulib-m4/pthread_rwlock_rdlock.m434
1 files changed, 28 insertions, 6 deletions
diff --git a/gnulib-m4/pthread_rwlock_rdlock.m4 b/gnulib-m4/pthread_rwlock_rdlock.m4
index 9c1d5d01..8ad78392 100644
--- a/gnulib-m4/pthread_rwlock_rdlock.m4
+++ b/gnulib-m4/pthread_rwlock_rdlock.m4
@@ -1,5 +1,5 @@
-# pthread_rwlock_rdlock.m4 serial 1
-dnl Copyright (C) 2017-2018 Free Software Foundation, Inc.
+# pthread_rwlock_rdlock.m4 serial 4
+dnl Copyright (C) 2017-2022 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
@@ -23,15 +23,19 @@ dnl time, a phenomenon called "writer starvation".
dnl Without such a guarantee, applications have a hard time avoiding writer
dnl starvation.
dnl
-dnl POSIX:2008 makes this requirement only for implementations that support TPS
+dnl POSIX:2017 makes this requirement only for implementations that support TPS
dnl (Thread Priority Scheduling) and only for the scheduling policies SCHED_FIFO
dnl and SCHED_RR, see
-dnl http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_rdlock.html
-dnl but test verifies the guarantee regardless of TPS and regardless of
+dnl https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_rdlock.html
+dnl but this test verifies the guarantee regardless of TPS and regardless of
dnl scheduling policy.
+dnl Glibc does not provide this guarantee (and never will on Linux), see
+dnl https://sourceware.org/bugzilla/show_bug.cgi?id=13701
+dnl https://bugzilla.redhat.com/show_bug.cgi?id=1410052
AC_DEFUN([gl_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER],
[
AC_REQUIRE([gl_THREADLIB_EARLY])
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CACHE_CHECK([whether pthread_rwlock_rdlock prefers a writer to a reader],
[gl_cv_pthread_rwlock_rdlock_prefer_writer],
[save_LIBS="$LIBS"
@@ -151,7 +155,25 @@ main ()
]])],
[gl_cv_pthread_rwlock_rdlock_prefer_writer=yes],
[gl_cv_pthread_rwlock_rdlock_prefer_writer=no],
- [gl_cv_pthread_rwlock_rdlock_prefer_writer="guessing yes"])
+ [case "$host_os" in
+ # Guess no on glibc systems.
+ *-gnu* | gnu*) gl_cv_pthread_rwlock_rdlock_prefer_writer="guessing no" ;;
+ # Guess no on musl systems.
+ *-musl*) gl_cv_pthread_rwlock_rdlock_prefer_writer="guessing no" ;;
+ # Guess no on bionic systems.
+ *-android*) gl_cv_pthread_rwlock_rdlock_prefer_writer="guessing no" ;;
+ # Guess yes on native Windows with the mingw-w64 winpthreads library.
+ # Guess no on native Windows with the gnulib windows-rwlock module.
+ mingw*) if test "$gl_use_threads" = yes || test "$gl_use_threads" = posix; then
+ gl_cv_pthread_rwlock_rdlock_prefer_writer="guessing yes"
+ else
+ gl_cv_pthread_rwlock_rdlock_prefer_writer="guessing no"
+ fi
+ ;;
+ # If we don't know, obey --enable-cross-guesses.
+ *) gl_cv_pthread_rwlock_rdlock_prefer_writer="$gl_cross_guess_normal" ;;
+ esac
+ ])
LIBS="$save_LIBS"
])
case "$gl_cv_pthread_rwlock_rdlock_prefer_writer" in