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See if SA_RESTART signals will interrupt select(). 

On some platforms (at least older HP-UXes such as 11.11, possibly others)
setting SA_RESTART on signal handers will cause it to not interrupt
select(), at least for calls that do not specify a timeout.  Try to
detect this and if found, don't use SA_RESTART.

POSIX says "If SA_RESTART has been set for the interrupting signal, it
is implementation-dependent whether select() restarts or returns with
[EINTR]" so this behaviour is within spec.
This commit is contained in:
Darren Tucker 2020-05-01 15:09:26 +10:00
parent 90a0b434ed
commit 6c6072ba8b
2 changed files with 39 additions and 0 deletions
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37
configure.ac
View File

@ -2500,6 +2500,43 @@ static void sighandler(int sig) { _exit(1); }
)
fi
AC_MSG_CHECKING([if SA_RESTARTed signals interrupt select()])
AC_RUN_IFELSE(
[AC_LANG_PROGRAM([[
#ifdef HAVE_SYS_SELECT
# include <sys/select.h>
#endif
#include <sys/types.h>
#include <sys/time.h>
#include <stdlib.h>
#include <signal.h>
static void sighandler(int sig) { }
]], [[
int r;
pid_t pid;
struct sigaction sa;
sa.sa_handler = sighandler;
sa.sa_flags = SA_RESTART;
(void)sigaction(SIGTERM, &sa, NULL);
if ((pid = fork()) == 0) { /* child */
sleep(1);
kill(getppid(), SIGTERM);
sleep(1);
kill(getppid(), SIGKILL);
exit(0);
} else { /* parent */
r = select(0, NULL, NULL, NULL, NULL);
}
exit(r == -1 ? 0 : 1);
]])],
[AC_MSG_RESULT([yes])],
[AC_MSG_RESULT([no])
AC_DEFINE([NO_SA_RESTART], [1],
[SA_RESTARTed signals do no interrupt select])],
[AC_MSG_WARN([cross compiling: assuming yes])]
)
AC_CHECK_FUNCS([getpgrp],[
AC_MSG_CHECKING([if getpgrp accepts zero args])
AC_COMPILE_IFELSE(

2
misc.c
View File

@ -2258,8 +2258,10 @@ ssh_signal(int signum, sshsig_t handler)
memset(&sa, 0, sizeof(sa));
sa.sa_handler = handler;
sigfillset(&sa.sa_mask);
#if defined(SA_RESTART) && !defined(NO_SA_RESTART)
if (signum != SIGALRM)
sa.sa_flags = SA_RESTART;
#endif
if (sigaction(signum, &sa, &osa) == -1) {
debug3("sigaction(%s): %s", strsignal(signum), strerror(errno));
return SIG_ERR;