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Cygwin: serial: revamp overlapped IO in read and select

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Get rid of WaitCommEvent and using overlapped_armed to share the
same overlapped operation between read and select.  Rather, make
sure to cancel the overlapped IO before leaving any of these functions.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen
2020-03-18 21:14:06 +01:00
parent 93b491c4f2
commit 2929599590
4 changed files with 85 additions and 199 deletions
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163
winsup/cygwin/select.cc
View File

@@ -1434,22 +1434,15 @@ fhandler_dev_null::select_except (select_stuff *ss)
return s;
}
static int start_thread_serial (select_record *me, select_stuff *stuff);
static int
peek_serial (select_record *s, bool)
{
HANDLE h;
COMSTAT st;
DWORD event, io_err;
DWORD io_err;
fhandler_serial *fh = (fhandler_serial *) s->fh;
if (fh->get_readahead_valid ())
return s->read_ready = true;
select_printf ("fh->overlapped_armed %d", fh->overlapped_armed);
HANDLE h;
set_handle_or_return_if_not_open (h, s);
if ((s->read_selected && s->read_ready)
@@ -1459,55 +1452,16 @@ peek_serial (select_record *s, bool)
return true;
}
/* This is apparently necessary for the com0com driver.
See: http://cygwin.com/ml/cygwin/2009-01/msg00667.html */
SetCommMask (h, 0);
if (fh->get_readahead_valid ())
return s->read_ready = true;
SetCommMask (h, EV_RXCHAR);
if (!fh->overlapped_armed)
if (!ClearCommError (h, &io_err, &st))
{
COMSTAT st;
ResetEvent (fh->io_status.hEvent);
if (!ClearCommError (h, &io_err, &st))
{
debug_printf ("ClearCommError %E");
goto err;
}
if (st.cbInQue)
return s->read_ready = true;
if (WaitCommEvent (h, &event, &fh->io_status))
return s->read_ready = true;
if (GetLastError () != ERROR_IO_PENDING)
{
debug_printf ("WaitCommEvent %E");
goto err;
}
fh->overlapped_armed = 1;
}
switch (WaitForSingleObject (fh->io_status.hEvent, 10L))
{
case WAIT_OBJECT_0:
if (!ClearCommError (h, &io_err, &st))
{
debug_printf ("ClearCommError %E");
goto err;
}
if (st.cbInQue)
{
select_printf ("got something");
return s->read_ready = true;
}
break;
case WAIT_TIMEOUT:
break;
default:
debug_printf ("WaitForMultipleObjects %E");
debug_printf ("ClearCommError %E");
goto err;
}
if (st.cbInQue)
return s->read_ready = true;
return 0;
@@ -1515,84 +1469,49 @@ err:
if (GetLastError () == ERROR_OPERATION_ABORTED)
{
select_printf ("operation aborted");
return 0;
return false;
}
s->set_select_errno ();
return -1;
}
static DWORD WINAPI
thread_serial (void *arg)
{
select_serial_info *si = (select_serial_info *) arg;
bool looping = true;
while (looping)
for (select_record *s = si->start; (s = s->next); )
if (s->startup != start_thread_serial)
continue;
else
{
if (peek_serial (s, true))
looping = false;
if (si->stop_thread)
{
select_printf ("stopping");
looping = false;
break;
}
}
select_printf ("exiting");
return 0;
}
static int
start_thread_serial (select_record *me, select_stuff *stuff)
{
if (stuff->device_specific_serial)
me->h = *((select_serial_info *) stuff->device_specific_serial)->thread;
else
{
select_serial_info *si = new select_serial_info;
si->start = &stuff->start;
si->stop_thread = false;
si->thread = new cygthread (thread_serial, si, "sersel");
me->h = *si->thread;
stuff->device_specific_serial = si;
}
return 1;
}
static void
serial_cleanup (select_record *, select_stuff *stuff)
serial_read_cleanup (select_record *s, select_stuff *stuff)
{
select_serial_info *si = (select_serial_info *) stuff->device_specific_serial;
if (!si)
return;
if (si->thread)
if (s->h)
{
si->stop_thread = true;
si->thread->detach ();
fhandler_serial *fh = (fhandler_serial *) s->fh;
HANDLE h = fh->get_handle_cyg ();
DWORD undefined;
if (h)
{
CancelIo (h);
GetOverlappedResult (h, &fh->io_status, &undefined, TRUE);
}
}
delete si;
stuff->device_specific_serial = NULL;
}
select_record *
fhandler_serial::select_read (select_stuff *ss)
{
DWORD event;
select_record *s = ss->start.next;
if (!s->startup)
{
s->startup = start_thread_serial;
s->verify = verify_ok;
s->cleanup = serial_cleanup;
}
s->startup = no_startup;
s->verify = verify_ok;
s->cleanup = serial_read_cleanup;
s->peek = peek_serial;
s->read_selected = true;
s->read_ready = false;
/* This is apparently necessary for the com0com driver.
See: http://cygwin.com/ml/cygwin/2009-01/msg00667.html */
SetCommMask (get_handle_cyg (), 0);
SetCommMask (get_handle_cyg (), EV_RXCHAR);
if (!WaitCommEvent (get_handle_cyg (), &event, &io_status)
&& GetLastError () == ERROR_IO_PENDING)
s->h = io_status.hEvent;
return s;
}
@@ -1600,13 +1519,10 @@ select_record *
fhandler_serial::select_write (select_stuff *ss)
{
select_record *s = ss->start.next;
if (!s->startup)
{
s->startup = no_startup;
s->verify = verify_ok;
}
s->startup = no_startup;
s->verify = verify_ok;
s->peek = peek_serial;
s->h = get_handle ();
s->write_selected = true;
s->write_ready = true;
return s;
@@ -1616,12 +1532,9 @@ select_record *
fhandler_serial::select_except (select_stuff *ss)
{
select_record *s = ss->start.next;
if (!s->startup)
{
s->startup = no_startup;
s->verify = verify_ok;
}
s->h = NULL;
s->startup = no_startup;
s->verify = verify_ok;
s->peek = peek_serial;
s->except_selected = false; // Can't do this
s->except_ready = false;