Date: Sat, 04 Dec 2010 22:32:57 +0200 From: Andriy Gapon <avg@freebsd.org> To: Brandon Gooch <jamesbrandongooch@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: DTrace: Sending ^C while running script produces no output Message-ID: <4CFAA579.1010701@freebsd.org> In-Reply-To: <AANLkTikmxpRQY_nOD6SB32-nd7YTTgysv2zWgzv7ozYy@mail.gmail.com> References: <AANLkTikmxpRQY_nOD6SB32-nd7YTTgysv2zWgzv7ozYy@mail.gmail.com>
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on 03/12/2010 07:20 Brandon Gooch said the following: > I've been tinkering with DTrace a bit, and I've notice something > peculiar on each system I've tried it on. > > Sending ^C from the keyboard in the terminal (console, XTerm, Konsole) > produces no output [1]. Can you ktrace the dtrace process? I wonder, could it be that SIGINT from ^C is somehow delivered twice?.. > For example, while trying out a one-liner (from > http://www.brendangregg.com/DTrace/dtrace_oneliners.txt): > > brandon@d820:~$ sudo dtrace -n 'syscall:::entry { @num[execname] = count(); }' > dtrace: description 'syscall:::entry ' matched 514 probes > ^C BTW, sudo might play a role here... Just a thought. > brandon@d820:~$ (12-02 23:11) > > > If I instead, from another terminal, use pkill to quit or terminate > the process, I get output: > > brandon@d820:~$ sudo dtrace -n 'syscall:::entry { @num[execname] = count(); }'; > dtrace: description 'syscall:::entry ' matched 514 probes > > > akonadi_control 4 > akonadiserver 5 > syslogd 6 > sendmail 8 > akonadi_ical_resour 12 > akonadi_maildir_res 12 > akonadi_nepomuk_con 12 > akonadi_vcard_resou 12 > kuiserver 12 > akonadi_maildispatc 14 > korgac 14 > virtuoso-t 15 > dbus-daemon 17 > mysqld 18 > hald 24 > knotify4 27 > akonadi_contacts_re 36 > nepomukservicestub 70 > pkill 70 > powerd 72 > dtrace 101 > zsh 111 > sudo 495 > kwin 2812 > firefox-bin 3175 > kdeinit4 11044 > Xorg 39588 > brandon@d820:~$ (12-02 23:14) > > > I also want to add that I've tried this with a variety of shells on > both 8.2-PRERELEASE and HEAD systems, i386 and amd64, built with GCC > and nearly GENERIC kernels in order to try to eliminate the cause. > > I feel as though this has something to do with file descriptors being > closed too soon when handling the signal or something of that nature. > It's also been suggested that this could be a bug in libdtrace, but I > haven't the knowledge (or skill) to try and pinpoint the cause myself. > > Is there anyone here that may be able to provide feedback or debugging > suggestions? > > Thanks! > > -Brandon > > [1] This isn't always the case, only like 99.99% of the time. > Sometimes I do get output, but usually it's just snippets, and > sometimes random characters! -- Andriy Gapon
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