From: Wichert Akkerman <wichert@deephackmode.org>
Date: Fri, 26 Nov 1999 13:11:29 +0000 (+0000)
Subject: Add pollhack
X-Git-Tag: v4.5.18~1159
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9dbf15466e9c178ac4090eba2c1232e2fe0706f9;p=strace

Add pollhack
---

diff --git a/ChangeLog b/ChangeLog
index c6483c5c..bd679dbc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,7 @@ Fri Nov 26 10:51:55 CET 1999 Wichert Akkerman <wakkerma@debian.org>
     + allow net.c to compile on systems without AF_INET6
     + Only use long_to_sigset on Linux systems
     + UnixWare treats sigmask_t and sigmask_t* as the same thing
+    + Add pollhack
 
 Fri Nov 26 01:28:09 CET 1999 Wichert Akkerman <wakkerma@debian.org>
 
diff --git a/README-svr4 b/README-svr4
index 82febf77..8f66a7fd 100644
--- a/README-svr4
+++ b/README-svr4
@@ -16,5 +16,14 @@ on UnixWare 2.1 you need to add the following to config.h yourself:
     #define UNIXWARE 2
     #define HAVE_POLLABLE_PROCFS 1
 
+On UnixWare using the -f option to follow forked children sometimes shows
+many "unfinished" system calls as strace bounces between each runnable child.
+A crude workaround for this is available by adding
+
+    #define POLL_HACK 1
+
+to the config.h file.  This forces strace to check whether the last process
+has finished a system call before polling other processes for events.
+
 Wichert Akkerman <wakkerma@debian.org>
 
diff --git a/strace.c b/strace.c
index 45390b4d..f40f5d63 100644
--- a/strace.c
+++ b/strace.c
@@ -1243,6 +1243,9 @@ choose_pfd()
 static int
 trace()
 {
+#ifdef POLL_HACK
+	struct tcb *in_syscall;
+#endif
 	struct tcb *tcp;
 	int pfd;
 	int what;
@@ -1274,6 +1277,28 @@ trace()
 #endif /* !HAVE_POLLABLE_PROCFS */
 		default:
 #ifdef HAVE_POLLABLE_PROCFS
+#ifdef POLL_HACK
+		        /* On some systems (e.g. UnixWare) we get too much ugly
+			   "unfinished..." stuff when multiple proceses are in
+			   syscalls.  Here's a nasty hack */
+		    
+			if (in_syscall) {
+				struct pollfd pv;
+				tcp = in_syscall;
+				in_syscall = NULL;
+				pv.fd = tcp->pfd;
+				pv.events = POLLWANT;
+				if ((what = poll (&pv, 1, 1)) < 0) {
+					if (interrupted)
+						return 0;
+					continue;
+				}
+				else if (what == 1 && pv.revents & POLLWANT) {
+					goto FOUND;
+				}
+			}
+#endif
+
 			if (poll(pollv, nprocs, INFTIM) < 0) {
 				if (interrupted)
 					return 0;
@@ -1297,6 +1322,7 @@ trace()
 			fprintf(stderr, "unknown pfd: %u\n", pfd);
 			exit(1);
 		}
+	FOUND:
 		/* Get the status of the process. */
 		if (!interrupted) {
 			ioctl_result = IOCTL_WSTOP (tcp);
@@ -1358,6 +1384,9 @@ trace()
 			}
 			break;
 		case PR_SYSENTRY:
+#ifdef POLL_HACK
+		        in_syscall = tcp;
+#endif
 		case PR_SYSEXIT:
 			if (trace_syscall(tcp) < 0) {
 				fprintf(stderr, "syscall trouble\n");