Re: why "in_sighandler"?

[Jan Djärv]

YAMAMOTO Mitsuharu skrev:
> > > > > > On Mon, 21 Aug 2006 09:19:13 +0200, Jan Djärv <address@hidden> said:
>
> > Read the single exception: "when a signal interrupts an unsafe
> > function and the signal-catching function calls an unsafe function,
> > the behavior is undefined."
>
> So, you interpret that ``what are interrupted by a signal'' are all
> the functions in execution on the whole threads in the process, not
> just a single function in execution on the thread that the signal is
> delivered to?  I don't think that is a natural interpretation.

I don't see the line "what are interrupted by a signal" in the quote, so I'm 
not sure what you mean.

My interpretation is that it is unsafe to call lock/unlock from a thread and 
from a signal handler at the same time, if they operate on the same mutex. 
That is what the original hang was all about.

> > No, but in the presense of signal handlers executing malloc, there
> > is no scenario that is safe.  Your suggestion also has undefined
> > behaviour accoding to the quote from the standard.
>
> As I said earlier, the current Emacs implementation calls malloc
> within a signal handler with the help of BLOCK_INPUT relying on the
> assumption that it is safe unless the signal interrupted
> malloc-related functions.

But this only works for the Emacs main thread, not the Gnome threads.

        Jan D.