Subj : Re: asynchronous cancel vs calling pthread_exit in signal handler
To   : comp.unix.programmer,comp.programming.threads
From : Ben Hutchings
Date : Fri Apr 22 2005 10:15 pm

Dave wrote:
> I'm a newbie in MT programming and I've been reading PwPT about
> cancelling the execution of a thread.
> 
> I'm writing a database application which calls some 3rd party library
> to send SQL queries to the database but sometimes the database is not
> responsive and I would like to interrupt the call. Sending a signal
> doesn't interrupt the call every time so I would like to
> cancel/terminate the thread (deferred cancel doesn't work either).
> 
> From what I've read it seems that asynchronous cancel is definitely
> something that I shouldn't use. but I came across a suggestion of
> calling pthread_exit() in the signal handler, I wonder if that's just
> as dangerous as using asynchronous cancel?

I don't think any of the pthreads functions are safe to call in a
signal handler.  They're not listed in the table of signal-safe
functions in the latest version of SUS.  In any case exiting a
thread from a signal handler is liable to leave shared data in
an invalid state, just like asynchronous cancellation.

> Any help is appreciated. Thanks in advance.

-- 
Ben Hutchings
If the facts do not conform to your theory, they must be disposed of.

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