Attachment 1044 Details for Bug 1135 – debug session and source code snippets pinpointing the problem

debug session and source code snippets pinpointing the problem

debug_session.txt (text/plain), 3.99 KB, created by Anastasius Focht on 2005-12-16 20:55:51 AEDT

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Creator: Anastasius Focht

Created: 2005-12-16 20:55:51 AEDT

Size: 3.99 KB

patch

obsolete

>In my ".bashrc"
>
>---- snip .bashrc ---
>
>[ -z "$SSH_AUTH_SOCK" ] && eval `ssh-agent -s`
>[ -z "$SSH_AGENT_PID" ] || ssh-add -l >/dev/null 2>&1 || ssh-add
>
>And ".logout"
>
>---- snip .lgout -----
>
>kill $SSH_AGENT_PID
>
>---- snip -----
>
>When i update my cygwin installation using "setup.exe" i occasionally
>get the ssh-agent hanging while eating 100% cpu.
>This happens while the Cygwin Setup Post-Install Script runs.
>If i renice the "ssh-agent" process, setup (gui) exits cleanly but the
>process is eating cpu forever.
>
>$ ssh -V
>OpenSSH_4.2p1, OpenSSL 0.9.8a 11 Oct 2005
>
>Using my favorite win32 user mode debugger, ollydbg:
>
>---- snip -----
>
>Threads
>Ident      Entry      Data block   Last error
>Status      Priority   User time     System time
>0000056C   7C810856   7FFDD000     ERROR_SUCCESS (00000000)
>Paused       32 + 0       0.0000 s      0.0000 s
>00000C4C   00000000   7FFDF000     ERROR_IO_PENDING (000003E5)
>Active       32 - 15     18.6250 s     29.1718 s
>00000F9C   7C810856   7FFDE000     ERROR_SUCCESS (00000000)
>Paused       32 + 0       0.0000 s      0.0000 s
>
>---- snip -----
>
>Thread 0xc4c is eating cpu (32-15 = reniced it to idle prio) forever.
>
>I debugged thru disassembly and using cygwin dll symbols + ssh-agent
>sources (dont have debug symbols)...
>
>----------------snip ssh-agent.c -----------------------------
>
>http://www.openbsd.org/cgi-bin/cvsweb/~checkout~/src/usr.bin/ssh/ssh-age
>nt.c?rev=1.123&content-type=text/plain
>
>skip:
>	new_socket(AUTH_SOCKET, sock);
>	if (ac > 0) {
>		signal(SIGALRM, check_parent_exists);
>		alarm(10);
>	}
>	idtab_init();
>	if (!d_flag)
>		signal(SIGINT, SIG_IGN);
>	signal(SIGPIPE, SIG_IGN);
>	signal(SIGHUP, cleanup_handler);
>	signal(SIGTERM, cleanup_handler);
>	nalloc = 0;
>
>	while (1) {
>		prepare_select(&readsetp, &writesetp, &max_fd, &nalloc);
>		if (select(max_fd + 1, readsetp, writesetp, NULL, NULL)
>< 0) {
>			if (errno == EINTR)
>				continue;
>			fatal("select: %s", strerror(errno));
>		}
>		after_select(readsetp, writesetp);
>	}
>	/* NOTREACHED */
>}
>
>
>static void
>after_select(fd_set *readset, fd_set *writeset)
>{
>	struct sockaddr_un sunaddr;
>	socklen_t slen;
>	char buf[1024];
>	int len, sock;
>	u_int i;
>	uid_t euid;
>	gid_t egid;
>
>	for (i = 0; i < sockets_alloc; i++)
>		switch (sockets[i].type) {
>		case AUTH_UNUSED:
>			break;
>		case AUTH_SOCKET:
>			if (FD_ISSET(sockets[i].fd, readset)) {
>				slen = sizeof(sunaddr);
>				sock = accept(sockets[i].fd,
>				    (struct sockaddr *) &sunaddr,
>&slen);
>				if (sock < 0) {
>					error("accept from AUTH_SOCKET:
>%s",
>					    strerror(errno));
>					break;
>				}
>
>----------------snip ssh-agent.c -----------------------------
>
>0022EE0C   00402F7C  ssh-agen.00402F7C
>0022EE10   00000001  |nfds = 1
>0022EE14   004754E0  |Readfds = 004754E0
>0022EE18   004754F0  |Writefds = 004754F0
>0022EE1C   00000000  |Exceptfds = NULL
>0022EE20   00000000  \pTimeout = NULL
>0022EE24   00350688
>0022EE28   0022EF00
>0022EE2C   00000764
>0022EE30   7C81B808  RETURN to kernel32.7C81B808 from kernel32.7C80250B
>0022EE34   0022D238
>0022EE38   61133000  ASCII "Cygwin Setup Post-Install Script"
>
>----------------snip -----------------------------
>
>The problem is the following (forever) loop:
>
>----
>
>while (1) {
>		prepare_select(&readsetp, &writesetp, &max_fd, &nalloc);
>		if (select(max_fd + 1, readsetp, writesetp, NULL, NULL)
>< 0) {
>			if (errno == EINTR)
>				continue;
>			fatal("select: %s", strerror(errno));
>		}
>		after_select(readsetp, writesetp);
>	}
>----
>
>"int cygwin_select(int, _types_fd_set*, _types_fd_set*, _types_fd_set*,
>timeval*)" 
>
>in ssh-agents's main is returning "1" (eax)
>
>"after_select" is called which calls "cygwin1.accept()"
>
>"accept" returns "-1" (eax) and lasterror/errno is 0x6C
>
>errno = 0x6C -> #define	ESHUTDOWN	108	/* Cannot send after
>transport endpoint shutdown */
>
>-----
>
>The main question is: can cygwin's "select" be successful and following
>"accept" fail due to non-socket?
>
>Is the problem openssh or cygwin related?
>Any thoughts?

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