Re: [PATCH 2/2] posix-cpu-timers: use ->sighand instead of ->signal to check the task is alive

[Roland McGrath <roland@redhat.com>]

> It doesn't matter which pointer to check under tasklist to ensure the task
> was not released, ->signal or ->sighand. But we are going to make ->signal
> refcountable, change the code to use ->sighand.

I haven't been following what that's about (signal_struct already has two
atomic counts!).  Uses here protecting cpu_clock_sample_group() e.g., are
around looking at ->signal->foobar, so if ->signal is still there, why not
look at it and be able to get the sample in whatever small window this is?

I don't really understand what this new case might mean though.  Most
things that look at ->signal need to lock it, so access doesn't make any
sense if there is no siglock because ->sighand is clear while ->signal is not.


Thanks,
Roland