Ignore - not just block - SIGALRM around Popen()/Pclose().

Because our "popen" implementation uses stdio, and because nobody's stdio
library is capable of surviving signals, we need to make absolutely sure
that we hide the SIGALRM from the smart scheduler.  Otherwise, when you
open a menu in openoffice, and it recompiles XKB to deal with the
accelerators, and you popen xkbcomp because we suck, then the scheduler
will tell you you're taking forever doing something stupid, and the
wait() code will get confused, and input will hang and your CPU usage
slams to 100%.  Down, not across.

1 files changed, 8 insertions, 0 deletions

diff --git a/os/utils.c b/os/utils.c
index 3bb7dbeba..afcaae41b 100644
--- a/os/utils.c
+++ b/os/utils.c
@@ -1720,6 +1720,8 @@ static struct pid {
     int pid;
 } *pidlist;
 
+static sighandler_t old_alarm = NULL; /* XXX horrible awful hack */
+
 pointer
 Popen(char *command, char *type)
 {
@@ -1741,11 +1743,15 @@ Popen(char *command, char *type)
 	return NULL;
     }
 
+    /* Ignore the smart scheduler while this is going on */
+    old_alarm = signal(SIGALRM, SIG_IGN);
+
     switch (pid = fork()) {
     case -1: 	/* error */
 	close(pdes[0]);
 	close(pdes[1]);
 	xfree(cur);
+	signal(SIGALRM, old_alarm);
 	return NULL;
     case 0:	/* child */
 	if (setgid(getgid()) == -1)
@@ -1921,6 +1927,8 @@ Pclose(pointer iop)
     /* allow EINTR again */
     OsReleaseSignals ();
     
+    signal(SIGALRM, old_alarm);
+
     return pid == -1 ? -1 : pstat;
 }