From df1b0f580d3dc4dd165d84fbcc14d0eebd8ee2c4 Mon Sep 17 00:00:00 2001 From: Kyle Evans Date: Sun, 20 Apr 2025 22:19:17 -0500 Subject: [PATCH] time: switch to fences for siginfo_recvd This effectively reverts 6e824f3713011 ("time: siginfo_recvd needs to be marked volatile") because it was actually wrong. Switch to C11 signal fence, which provides a compiler barrier that will do the right thing. Reported by: kib Reviewed by: kib (slightly earlier version) Differential Revision: https://reviews.freebsd.org/D45574 --- usr.bin/time/time.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/usr.bin/time/time.c b/usr.bin/time/time.c index 4c1ce06543e..5478b23d52e 100644 --- a/usr.bin/time/time.c +++ b/usr.bin/time/time.c @@ -40,6 +40,8 @@ #include #include #include +#include +#include #include #include #include @@ -54,7 +56,7 @@ static void showtime(FILE *, struct timespec *, struct timespec *, static void siginfo(int); static void usage(void) __dead2; -static volatile sig_atomic_t siginfo_recvd; +static sig_atomic_t siginfo_recvd; static char decimal_point; static struct timespec before_ts; static int hflag, pflag; @@ -125,7 +127,10 @@ main(int argc, char **argv) (void)signal(SIGINFO, siginfo); (void)siginterrupt(SIGINFO, 1); while (wait4(pid, &status, 0, &ru) != pid) { - if (siginfo_recvd) { + bool do_siginfo = siginfo_recvd != 0; + + atomic_signal_fence(memory_order_acquire); + if (do_siginfo) { siginfo_recvd = 0; if (clock_gettime(CLOCK_MONOTONIC, &after)) err(1, "clock_gettime"); @@ -296,4 +301,5 @@ siginfo(int sig __unused) { siginfo_recvd = 1; + atomic_signal_fence(memory_order_release); }