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Cygwin: serial: select: call ClearCommError prior to calling WaitCommEvent 

This (hopefully) eliminates a race condition

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2020-03-23 17:23:19 +01:00
parent 3a74630f75
commit a1f0585454
1 changed files with 18 additions and 8 deletions
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26
winsup/cygwin/select.cc
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@ -1502,6 +1502,9 @@ verify_serial (select_record *me, fd_set *rfds, fd_set *wfds, fd_set *efds)
select_record *
fhandler_serial::select_read (select_stuff *ss)
{
COMSTAT st;
DWORD io_err;
select_record *s = ss->start.next;
s->startup = no_startup;
@ -1512,18 +1515,25 @@ fhandler_serial::select_read (select_stuff *ss)
s->read_ready = false;
/* This is apparently necessary for the com0com driver.
See: http://cygwin.com/ml/cygwin/2009-01/msg00667.html */
ResetEvent (io_status.hEvent);
SetCommMask (get_handle_cyg (), 0);
SetCommMask (get_handle_cyg (), EV_RXCHAR);
ResetEvent (io_status.hEvent);
if (!WaitCommEvent (get_handle_cyg (), &event, &io_status))
if (ClearCommError (get_handle_cyg (), &io_err, &st) && st.cbInQue)
{
if (GetLastError () == ERROR_IO_PENDING)
s->h = io_status.hEvent;
else
select_printf ("WaitCommEvent %E");
s->read_ready = true;
return s;
}
else
s->read_ready = true;
if (WaitCommEvent (get_handle_cyg (), &event, &io_status))
{
s->read_ready = true;
return s;
}
if (GetLastError () == ERROR_IO_PENDING)
{
s->h = io_status.hEvent;
return s;
}
select_printf ("WaitCommEvent %E");
return s;
}