https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=7097b05eda2f8e9058eab4fda8dedacdfb7ffd7f
commit 7097b05eda2f8e9058eab4fda8dedacdfb7ffd7f
Author: Corinna Vinschen
Date: Fri Aug 16 16:36:06 2019 +0200
Cygwin: select: revamp non-polling code for signalfd
Rather than waiting for signalfd_select_wait in a thread, which is racy,
create a global event "my_pendingsigs_evt" which is set and reset by
wait_sig depending only on the fact if blocked signals are pending or not.
This in turn allows to WFMO on this event in select as soon as signalfds
are present in the read descriptor set. Select's peek and verify
will then check if one of the present signalfds is affected.
Signed-off-by: Corinna Vinschen
Diff:
---
winsup/cygwin/cygtls.h | 2 +-
winsup/cygwin/exceptions.cc | 8 -
winsup/cygwin/select.cc | 80 +++-
winsup/cygwin/select.h | 11 ++
winsup/cygwin/signal.cc | 1 -
winsup/cygwin/sigproc.cc | 17 ++
winsup/cygwin/tlsoffsets.h | 16 -
winsup/cygwin/tlsoffsets64.h | 16 -
8 files changed, 40 insertions(+), 111 deletions(-)
diff --git a/winsup/cygwin/cygtls.h b/winsup/cygwin/cygtls.h
index 65a905c..a2e3676 100644
--- a/winsup/cygwin/cygtls.h
+++ b/winsup/cygwin/cygtls.h
@@ -189,8 +189,8 @@ 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. */
diff --git a/winsup/cygwin/exceptions.cc b/winsup/cygwin/exceptions.cc
index 1765f43..848f9bd 100644
--- a/winsup/cygwin/exceptions.cc
+++ b/winsup/cygwin/exceptions.cc
@@ -1469,14 +1469,6 @@ sigpacket::process ()
if (issig_wait)
{
tls->sigwait_mask = 0;
- /* If the catching thread is running select on a signalfd, don't call
-the signal handler and don't remove the signal from the queue. */
- if (tls->signalfd_select_wait)
- {
- SetEvent (tls->signalfd_select_wait);
- rc = 0;
- goto done;
- }
goto dosig;
}
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index 4e9256b..ac73e0a 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -1849,80 +1849,6 @@ fhandler_windows::select_except (select_stuff *ss)
return s;
}
-static int start_thread_signalfd (select_record *, select_stuff *);
-
-static DWORD WINAPI
-thread_signalfd (void *arg)
-{
- select_signalfd_info *si = (select_signalfd_info *) arg;
- bool event = false;
-
- while (!event)
-{
- sigset_t set = 0;
- _cygtls *tls = si->start->tls;
-
- for (select_record *s = si->start; (s = s->next); )
- if (s->startup == start_thread_signalfd)
- set |= ((fhandler_signalfd *) s->fh)->get_sigset ();
- set_signal_mask (tls->sigwait_mask, set);
- tls->signalfd_select_wait = si->evt;
- sig_dispatch_pending (true);
- switch (WaitForSingleObject (si->evt, INFINITE))
- {
- case WAIT_OBJECT_0:
- tls->signalfd_select_wait = NULL;
- event = true;
- break;
- default:
- break;
- }
- if (si->stop_thread)
- break;
- if (!event)
- Sleep (1L);
-}
- CloseHandle (si->evt);
- return 0;
-}
-
-static int
-start_thread_signalfd (select_record *me, select_stuff *stuff)
-{
- select_signalfd_info *si;
-
- if ((si = stuff->device_specific_signalfd))
-{
- me->h = *si->thread;
- return 1;
-}
- si = new select_signalfd_info;
- si->start = >start;
- si->stop_thread = false;
- si->evt = CreateEventW (_none_nih, TRUE, FALSE, NULL);
- si->thread = new cygthread (thread_signalfd, si, "signalfdsel");
- me->h = *si->thread;
- stuff->device_specific_signalfd = si;
- return 1;
-}
-
-static void
-signalfd_cleanup (select_record *, select_stuff *stuff)
-{
- select_signalfd_info *si;
-
- if (!(si = stuff->device_specific_signalfd))
-return;
- if (si->thread)
-{
- si->stop_thread = true;
- SetEvent (si->evt);
- si->thread->detach ();
-}
- delete si;
- stuff->device_specific_signalfd = NULL;
-}
-
static int
peek_signalfd (select_record *me, bool)
{
@@ -1942,17 +1868,19 @@ verify_signalfd (select_record *me, fd_set *rfds,
fd_set *wfds, fd_set *efds)
return peek_signalfd (me, true);
}
+extern HANDLE my_pendingsigs_evt;
+
select_record *
fhandler_signalfd::select_read (select_stuff *stuff)
{
select_record *s = stuff->start.next;
if (!s->startup)
{
- s->startup = start_thread_signalfd;
+ s->startup = no_startup;
s->verify = verify_signalfd;
- s->cleanup = signalfd_cleanup;
}
s->peek = peek_signalfd;
+ s->h =
