[newlib-cygwin] Cygwin: signalfd: implement non-polling select
Corinna Vinschen
corinna-cygwin@cygwin.com
Wed Jan 16 14:42:00 GMT 2019
On Jan 16 07:09, Ryan Johnson wrote:
> On 1/15/2019 4:22 AM, Corinna Vinschen wrote:
> > On Jan 15 10:50, Václav Haisman wrote:
> > > On Mon, 14 Jan 2019 at 17:19, Corinna Vinschen <corinna@sourceware.org> wrote:
> > > > https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=f42776fa781de858a927bc03aa966a0f3096b581
> > > >
> > > > commit f42776fa781de858a927bc03aa966a0f3096b581
> > > > Author: Corinna Vinschen <corinna@vinschen.de>
> > > > Date: Mon Jan 14 17:19:37 2019 +0100
> > > >
> > > > Cygwin: signalfd: implement non-polling select
> > > >
> > > > Allow the signal thread to recognize we're called in consequence of
> > > > select on a signalfd. If the signal is part of the wait mask, don't
> > > > call any signal handler and don't remove the signal from the queue,
> > > > so a subsequent read (or sigwaitinfo/sigtimedwait) still gets the
> > > > signal. Instead, just signal the event object at
> > > > _cygtls::signalfd_select_wait for the thread running select.
> > > >
> > > > The addition of signalfd_select_wait to _cygtls unearthed the alignment
> > > > problem of the context member again. To make sure this doesn't get lost,
> > > > improve the related comment in the header file so that this (hopefully)
> > > > doesn't get lost (again).
> > > >
> > > > Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
> > > > [...]
> > > >
> > > > diff --git a/winsup/cygwin/cygtls.h b/winsup/cygwin/cygtls.h
> > > > index 39dba13..65a905c 100644
> > > > --- a/winsup/cygwin/cygtls.h
> > > > +++ b/winsup/cygwin/cygtls.h
> > > > @@ -189,8 +189,11 @@ public:
> > > > stack_t altstack;
> > > > siginfo_t *sigwait_info;
> > > > HANDLE signal_arrived;
> > > > + HANDLE signalfd_select_wait;
> > > > bool will_wait_for_signal;
> > > > - long __align; /* Needed to align context to 16 byte. */
> > > > + /* context MUST be aligned to 16 byte, otherwise RtlCaptureContext fails.
> > > > + If you prepend cygtls members here, make sure context stays 16 byte
> > > > + aligned. */
> > > > ucontext_t context;
> > > > [...]
> > > Would it not better to do this with `ucontext_t context
> > > __attribute__((__aligned__(16)));` instead?
> > In theory yes, but it doesn't work. The simple perl parser in
> > gentls_offsets doesn't understand __attribute__ and screws up,
> > so generating tlsoffsets{64}.h fails.
>
> Why not introduce a typedef in some convenient location the perl script
> doesn't examine, e.g.
>
> typedef ucontext_t __attribute__((aligned(16))) aligned_ucontext_t;
>
> And then use that in the struct?
>
> Ryan
Great idea... it just doesn't work either, same as
https://cygwin.com/ml/cygwin-developers/2019-01/msg00006.html
Corinna
--
Corinna Vinschen
Cygwin Maintainer
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://cygwin.com/pipermail/cygwin-developers/attachments/20190116/deee1a60/attachment.sig>
More information about the Cygwin-developers
mailing list