Date: Sun, 9 Nov 2003 13:01:55 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: bde@zeta.org.au Cc: current@FreeBSD.org Subject: Re: serial console oddity Message-ID: <200311092102.hA9L1teF064564@gw.catspoiler.org> In-Reply-To: <200311091030.hA9AUGeF063359@gw.catspoiler.org>
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On 9 Nov, Don Lewis wrote: > On 9 Nov, Bruce Evans wrote: >> On Sat, 8 Nov 2003, Don Lewis wrote: >>> This is totally consistent until I "kill >>> -HUP" syslogd, which I believe causes syslogd to close and open >>> /dev/console, after which the syslog output appears correct on the >>> console. When the syslogd output is being corrupted, I can cat a file to >>> /dev/console and the output appears to be correct. >> >> When I debugged this, syslogd didn't seem to keep the console open, >> so the open()/close() in ttymsg() always caused the problem. I didn't >> notice killing syslogd makes a difference. Perhaps it helps due to a >> missing close. Holding the console open may be a workaround or even >> the correct fix. It's not clear where this should be done (should all >> clients of ttymsg() do it?). Running getty on the console or on the >> underlying tty device should do it accidentally. > > It looks to me like syslogd keeps the console open in addition to the > open()/close() in ttymsg(). cfline() calls open() on anything that > begins with '/' and calls isatty() to figure out whether it should set > the type to F_CONSOLE, F_TTY, or F_FILE, and init() closes the file > descriptor for all of these when syslogd is HUPed. > > I wonder if the console descriptor is getting revoked ... That appears to be the situation: scratch:~ 101>cat /var/run/syslog.pid 275 scratch:~ 102>fstat -p 275 USER CMD PID FD MOUNT INUM MODE SZ|DV R/W root syslogd 275 root / 2 drwxr-xr-x 1024 r root syslogd 275 wd / 2 drwxr-xr-x 1024 r root syslogd 275 text / 575452 -r-xr-xr-x 32204 r root syslogd 275 0 /dev 8 crw-rw-rw- null rw root syslogd 275 1 /dev 8 crw-rw-rw- null rw root syslogd 275 2 /dev 8 crw-rw-rw- null rw root syslogd 275 3* local dgram c6c97000 root syslogd 275 4* internet6 dgram udp c6c84ee0 root syslogd 275 5* internet dgram udp c6c85000 root syslogd 275 6 /dev 17 crw------- klog r root syslogd 275 8 - - bad - root syslogd 275 9 / 447635 -rw-r--r-- 45602 w root syslogd 275 10 / 450144 -rw------- 0 w root syslogd 275 11 / 448526 -rw------- 85593 w root syslogd 275 12 / 447600 -rw-r----- 3119 w root syslogd 275 13 / 450142 -rw-r--r-- 19324 w root syslogd 275 14 / 447744 -rw-r--r-- 274 w root syslogd 275 15 / 447492 -rw------- 19063 w root syslogd 275 16 / 448732 -rw------- 15508 w root syslogd 275 17 / 450145 -rw-r----- 0 w root syslogd 275 18 / 450146 -rw-r----- 0 w If we could somehow keep the console open, that would probably be a sufficient fix for the problem of discarded output. We probably don't care in the case of messages to users' terminals, since the users presumably have those devices open. There's no such guarantee in the case of the console. BTW, here's an example where I HUPed syslogd so that it works, but the rc script output is truncated. I think the partial message at the beginning of the 'vnlru' line should be "Stopping cron.". Nov 9 12:46:54 scratch shutdown: reboot by dl: Stopping inetd. Shutting down daemon processes:killall: Nov 9 12:46:56 scratch upsmon[504]: upsmon parent: exiting (child exited) warning: kill -TERM 504: No such process Nov 9 12:46:56 scratch kernel: pid 502 (upsd), uid 66: exited on signal 6 . Stopping cWaiting (max 60 seconds) for system process `vnlru' to stop...stopped Waiting (max 60 seconds) for system process `bufdaemon' to stop...stopped Waiting (max 60 seconds) for system process `syncer' to stop...stopped syncing disks, buffers remaining... 12 12 done Uptime: 13h34m21s Shutting down ACPI Rebooting...
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