Re: [PATCH -mm 3/3] proc: make task_sig() lockless

[Roland McGrath <roland@redhat.com>]

> Yes, /proc/pid/status can report the intermediate state, I even sent
> the updated changelog to document this.
> 
> But if you are not sure this is OK, I am worried. Do you think we should
> drop this patch? If yes, I won't argue.

I'm not dead-set against it, but I am hesitant.  My inclination is not to
remove any previous userland atomicity guarantees with regard to observable
signal state in any form.  At least, don't do that in part of a whole
cleanup flurry where it is intermixed with lots of changes that really are
pure cleanup with absolutely no userland-observable change.  If it really
helps to fragment what was atomic before, then we can consider it.  But
let's not be in a hurry.

David mentioned that users who do multiple reads due to using tiny buffers
already don't get atomic sampling.  That is certainly true but I don't
think it's relevant.  It is completely reliable that you can easily
allocate a buffer big enough to get all the Sig* fields on the first read,
and any user program that might care about the coherence of the data,
by definition, is already doing that.


Thanks,
Roland