This series addresses and ambiguity that is at least visible in OpenBSD, where zombie proceses would only be cleared after a new connection is received. The underlying problem is that when this code was originally introduced, SA_RESTART was not widely implemented, and the signal() call usually implemented SysV like semantics, at least until it started being reimplemented by calling sigaction() internally. Changes since v2 * Add a new patch 2 that modifies windows' sigaction so there is no more need for a fallback * Hopefully no more silly mistakes and a variable that finally makes sense Changes since v1 * Almost all references to siginterrupt has been removed and a better named variable used instead * Changes had been abstracted to minimize ifdefs and their introduction staged more naturally Carlo Marcelo Arenas Belón (4): compat/posix.h: track SA_RESTART fallback compat/mingw: allow sigaction(SIGCHLD) daemon: use sigaction() to install child_handler() daemon: explicitly allow EINTR during poll() Makefile | 5 +++++ compat/mingw-posix.h | 2 +- compat/mingw.c | 4 +++- compat/posix.h | 8 ++++++++ config.mak.uname | 7 ++++--- configure.ac | 16 ++++++++++++++++ daemon.c | 33 ++++++++++++++++++++++++++++----- meson.build | 4 ++++ 8 files changed, 69 insertions(+), 10 deletions(-) base-commit: cb3b40381e1d5ee32dde96521ad7cfd68eb308a6 Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2002%2Fcarenas%2Fsiginterrupt-v3 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2002/carenas/siginterrupt-v3 Pull-Request: https://github.com/git/git/pull/2002 Range-diff vs v2: 1: e82b7425bbc ! 1: ae1ca6bb2b2 compat/posix.h: track SA_RESTART fallback @@ Makefile: include shared.mak # when attempting to read from an fopen'ed directory (or even to fopen # it at all). # -+# Define USE_NON_POSIX_SIGNAL if don't have support for SA_RESTART or -+# prefer to use ANSI C signal() over POSIX sigaction() ++# Define NO_RESTARTABLE_SIGNALS if don't have support for SA_RESTART +# # Define OPEN_RETURNS_EINTR if your open() system call may return EINTR # when a signal is received (as opposed to restarting). @@ Makefile: ifdef FREAD_READS_DIRECTORIES COMPAT_CFLAGS += -DFREAD_READS_DIRECTORIES COMPAT_OBJS += compat/fopen.o endif -+ifdef USE_NON_POSIX_SIGNAL -+ COMPAT_CFLAGS += -DUSE_NON_POSIX_SIGNAL ++ifdef NO_RESTARTABLE_SIGNALS ++ COMPAT_CFLAGS += -DNO_RESTARTABLE_SIGNALS +endif ifdef OPEN_RETURNS_EINTR COMPAT_CFLAGS += -DOPEN_RETURNS_EINTR @@ compat/posix.h: char *gitdirname(char *); + * not on some systems (e.g. NonStop, QNX). + */ +#ifndef SA_RESTART -+# define SA_RESTART 0 /* disabled for sigaction() */ ++# define SA_RESTART 0 /* disabled for sigaction() */ +#endif + typedef uintmax_t timestamp_t; @@ config.mak.uname: ifeq ($(uname_S),Windows) NO_STRTOUMAX = YesPlease NO_MKDTEMP = YesPlease NO_INTTYPES_H = YesPlease -+ USE_NON_POSIX_SIGNAL = YesPlease ++ NO_RESTARTABLE_SIGNALS = YesPlease CSPRNG_METHOD = rtlgenrandom # VS2015 with UCRT claims that snprintf and friends are C99 compliant, # so we don't need this: @@ config.mak.uname: ifeq ($(uname_S),NONSTOP_KERNEL) NO_MMAP = YesPlease NO_POLL = YesPlease NO_INTPTR_T = UnfortunatelyYes -+ USE_NON_POSIX_SIGNAL = UnfortunatelyYes ++ NO_RESTARTABLE_SIGNALS = UnfortunatelyYes CSPRNG_METHOD = openssl SANE_TOOL_PATH = /usr/coreutils/bin:/usr/local/bin SHELL_PATH = /usr/coreutils/bin/bash @@ config.mak.uname: ifeq ($(uname_S),MINGW) NEEDS_LIBICONV = YesPlease NO_STRTOUMAX = YesPlease NO_MKDTEMP = YesPlease -+ USE_NON_POSIX_SIGNAL = YesPlease ++ NO_RESTARTABLE_SIGNALS = YesPlease NO_SVN_TESTS = YesPlease # The builtin FSMonitor requires Named Pipes and Threads on Windows. @@ config.mak.uname: ifeq ($(uname_S),QNX) NO_PTHREADS = YesPlease NO_STRCASESTR = YesPlease NO_STRLCPY = YesPlease -+ USE_NON_POSIX_SIGNAL = UnfortunatelyYes ++ NO_RESTARTABLE_SIGNALS = UnfortunatelyYes endif ## configure.ac ## @@ configure.ac: fi GIT_CONF_SUBST([ICONV_OMITS_BOM]) fi -+# Define USE_NON_POSIX_SIGNAL if don't have support for SA_RESTART or -+# prefer using ANSI C signal() over POSIX sigaction() ++# Define NO_RESTARTABLE_SIGNALS if don't have support for SA_RESTART + +AC_CACHE_CHECK([whether SA_RESTART is supported], [ac_cv_siginterrupt], [ + AC_COMPILE_IFELSE( + [AC_LANG_PROGRAM([#include <signal.h>], [[ -+ #ifdef SA_RESTART -+ #endif -+ siginterrupt(SIGCHLD, 1) -+ ]])],[ac_cv_siginterrupt=yes],[ ++ #ifdef SA_RESTART ++ restartable signals supported ++ #endif ++ ]])],[ + ac_cv_siginterrupt=no -+ USE_NON_POSIX_SIGNAL=UnfortunatelyYes -+ ] ++ NO_RESTARTABLE_SIGNALS=UnfortunatelyYes ++ ], [ac_cv_siginterrupt=yes] + ) +]) -+GIT_CONF_SUBST([USE_NON_POSIX_SIGNAL]) ++GIT_CONF_SUBST([NO_RESTARTABLE_SIGNALS]) + ## Checks for typedefs, structures, and compiler characteristics. AC_MSG_NOTICE([CHECKS for typedefs, structures, and compiler characteristics]) @@ meson.build: else endif +if compiler.get_define('SA_RESTART', prefix: '#include <signal.h>') == '' -+ libgit_c_args += '-DUSE_NON_POSIX_SIGNAL' ++ libgit_c_args += '-DNO_RESTARTABLE_SIGNALS' +endif + if not compiler.has_header('sys/select.h') -: ----------- > 2: 3f63479119f compat/mingw: allow sigaction(SIGCHLD) 2: 05d945aa1e5 ! 3: c66bda461f4 daemon: use sigaction() to install child_handler() @@ Commit message In a future change, the flags used for processing SIGCHLD will need to be updated, which is only possible by using sigaction(). - Factor out the call to set the signal handler and use sigaction instead - of signal for the systems that allow that, which has the added benefit - of using BSD semantics reliably and therefore not needing the rearming - call. + Replace signal() with an equivalent invocation of sigaction(), which + has the added benefit of using BSD semantics reliably and therefore + not needing the rearming call in the signal handler. Signed-off-by: Carlo Marcelo Arenas Belón <carenas@xxxxxxxxx> ## daemon.c ## @@ daemon.c: static void handle(int incoming, struct sockaddr *addr, socklen_t addrlen) - add_child(&cld, addr, addrlen); - } - --static void child_handler(int signo UNUSED) -+static void child_handler(int signo MAYBE_UNUSED) + static void child_handler(int signo UNUSED) { /* - * Otherwise empty handler because systemcalls will get interrupted @@ daemon.c: static void handle(int incoming, struct sockaddr *addr, socklen_t addr + * upon signal receipt. */ - signal(SIGCHLD, child_handler); -+#ifdef USE_NON_POSIX_SIGNAL -+ /* -+ * SysV needs the handler to be rearmed, but this is known -+ * to trigger infinite recursion crashes at least in AIX. -+ */ -+ signal(signo, child_handler); -+#endif } static int set_reuse_addr(int sockfd) @@ daemon.c: static void socksetup(struct string_list *listen_addr, int listen_port, struct s - } - } -+#ifndef USE_NON_POSIX_SIGNAL -+ -+static void set_signal_handler(struct sigaction *psa) -+{ -+ sigemptyset(&psa->sa_mask); -+ psa->sa_flags = SA_NOCLDSTOP | SA_RESTART; -+ psa->sa_handler = child_handler; -+ sigaction(SIGCHLD, psa, NULL); -+} -+ -+#else -+ -+static void set_signal_handler(struct sigaction *psa UNUSED) -+{ -+ signal(SIGCHLD, child_handler); -+} -+ static int service_loop(struct socketlist *socklist) { + struct sigaction sa; @@ daemon.c: static int service_loop(struct socketlist *socklist) } - signal(SIGCHLD, child_handler); -+ set_signal_handler(&sa); ++ sigemptyset(&sa.sa_mask); ++ sa.sa_flags = SA_NOCLDSTOP | SA_RESTART; ++ sa.sa_handler = child_handler; ++ sigaction(SIGCHLD, &sa, NULL); for (;;) { check_dead_children(); 3: b737e0389df ! 4: 851d663be0b daemon: explicitly allow EINTR during poll() @@ Commit message Signed-off-by: Carlo Marcelo Arenas Belón <carenas@xxxxxxxxx> ## daemon.c ## -@@ daemon.c: static void set_signal_handler(struct sigaction *psa) - sigaction(SIGCHLD, psa, NULL); +@@ daemon.c: static void socksetup(struct string_list *listen_addr, int listen_port, struct s + } } ++#ifndef NO_RESTARTABLE_SIGNALS ++ +static void set_sa_restart(struct sigaction *psa, int enable) +{ + if (enable) @@ daemon.c: static void set_signal_handler(struct sigaction *psa) + sigaction(SIGCHLD, psa, NULL); +} + - #else - - static void set_signal_handler(struct sigaction *psa UNUSED) -@@ daemon.c: static void set_signal_handler(struct sigaction *psa UNUSED) - signal(SIGCHLD, child_handler); - } - ++#else ++ +static void set_sa_restart(struct sigaction *psa UNUSED, int enable UNUSED) +{ +} -- gitgitgadget
