[patch] Make dbus-monitor flush its output on CTRL-C

Olli Salli olli.salli at collabora.co.uk
Wed Nov 8 09:47:46 PST 2006


a fine suggestion indeed. Attached is the updated patch.


On Wednesday 08 November 2006 20:16, Daniel P. Berrange wrote:
> On Wed, Nov 08, 2006 at 12:29:33PM -0500, Havoc Pennington wrote:
> > 
> > 
> > Olli Salli wrote:
> > >Hi,
> > >
> > >I noticed that when you run dbus-monitor redirecting its output to a file 
> > >and terminate it, its output in the file will be truncated due to stdio 
> > >buffers not getting flushed. This patch adds a SIGINT handler which 
> > >flushes the buffers and exits, so the full output is always present.
> > >
> > 
> > I thought glibc did this anyway? Maybe only for stderr?
> Yes, if you call 'exit' then all open streams are flushed.
> > I don't think it's technically allowed to do this in a signal handler, 
> > though of course it's harmless in practice. Patch seems fine. Maybe you 
> > want to add a comment "this isn't signal-safe but it's a best-effort 
> > thing" to avoid signal-safety police filing bugs. ;-)
> Neither exit or fflush are async-signal safe according to POSIX - if a
> second SIGINT arrives while flushing the first, then this will almost
> certainly deadlock due to non-reentrant locking used in the fflush call.
> The better way would be to just set a flag in the signal handler & and
> then have that flag checked in the while loop that dbus-monitor spins
> in. Assuming we've not set SA_RESTART for the signals, the receiving
> of the signal ought to cause the poll() to terminate early & thus the
> current iteration of the loop should finish.
> Regards,
> Dan.
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