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Fix lwsync instruction feature test

A feature test for the lwsync instruction performed on PowerPC
hardware at runtime system startup got into an eternal loop if
the instruction was not supported. This bug was introduced in
erts-5.9/OTP-R15B.
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1 parent 6088c2c commit 54507ec64c0b1e6b2b150c69b55eb84d08b07a15 @rickard-green rickard-green committed Dec 23, 2011
Showing with 34 additions and 15 deletions.
  1. +34 −15 erts/lib_src/pthread/ethread.c
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49 erts/lib_src/pthread/ethread.c
@@ -123,34 +123,53 @@ ethr_ts_event *ethr_get_tse__(void)
#if defined(ETHR_PPC_RUNTIME_CONF__)
-static volatile int lwsync_caused_sigill;
+#include <sys/wait.h>
static void
handle_lwsync_sigill(int signum)
{
- lwsync_caused_sigill = 1;
+ _exit(1);
}
static int
ppc_init__(void)
{
- struct sigaction act, oact;
- lwsync_caused_sigill = 0;
+ int pid;
- sigemptyset(&act.sa_mask);
- act.sa_flags = 0;
- act.sa_handler = handle_lwsync_sigill;
- if (sigaction(SIGILL, &act, &oact) != 0)
- return errno;
+ /* If anything what so ever failes we assume no lwsync for safety */
+ ethr_runtime__.conf.have_lwsync = 0;
+
+ /*
+ * We perform the lwsync test (which might cause an illegal
+ * instruction signal) in a separate process in order to be
+ * completely certain that we do not mess up our own state.
+ */
+ pid = fork();
+ if (pid == 0) {
+ struct sigaction act, oact;
- __asm__ __volatile__ ("lwsync\n\t" : : : "memory");
+ sigemptyset(&act.sa_mask);
+ act.sa_flags = SA_RESETHAND;
+ act.sa_handler = handle_lwsync_sigill;
+ if (sigaction(SIGILL, &act, &oact) != 0)
+ _exit(2);
- act.sa_flags = 0;
- act.sa_handler = SIG_DFL;
- if (sigaction(SIGILL, &act, &oact) != 0)
- return errno;
+ __asm__ __volatile__ ("lwsync\n\t" : : : "memory");
+
+ _exit(0);
+ }
- ethr_runtime__.conf.have_lwsync = (int) !lwsync_caused_sigill;
+ if (pid != -1) {
+ while (1) {
+ int status, res;
+ res = waitpid(pid, &status, 0);
+ if (res == pid) {
+ if (WIFEXITED(status) && WEXITSTATUS(status) == 0)
+ ethr_runtime__.conf.have_lwsync = 1;
+ break;
+ }
+ }
+ }
return 0;
}

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