Re: [Qemu-devel] [PATCH 2/2] qemu-ga: Add the guest-suspend command

[Luiz Capitulino <lcapitulino@redhat.com>]

On Mon, 16 Jan 2012 13:08:23 -0700
Eric Blake <eblake@redhat.com> wrote:

> On 01/16/2012 10:08 AM, Luiz Capitulino wrote:
> >> Strangely enough, POSIX doesn't include strcmp() in its list of
> >> async-signal-safe functions (which is what you should be restricting
> >> yourself to, if qemu-ga is multi-threaded), but in practice, I think
> >> that is a bug of omission in POSIX, and not something you have to change
> >> in your code.
> > 
> > memset() ins't either... sigaction() either, which begins to get
> > annoying.
> 
> sigaction() is required by POSIX to be async-signal-safe.  Where are you
> looking when claiming it isn't?

I did a bad search on:

 http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html

when I wrote that email. A few seconds later I saw that sigaction() is there.

> memset(), strlen, strcpy, and friends in <string.h> are all in the class
> of functions that I think are unintentional omissions from the list of
> async-signal-safe functions (they don't read/modify anything but the
> pointers passed in, so the _only_ reason I can think of why they _might_
> have been omitted from the list is that there might be some machine
> state that could be observably different if you were interrupted in the
> middle of one of these operations, such as a processor flag bit when
> using a rep prefix on x86 controlling which direction to move, but no
> one has ever pointed me to a definitive answer to why they were omitted).

If this is right we shouldn't be using them then...