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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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111
winsup/cygwin/fhandler_serial.cc
View File

@@ -35,15 +35,14 @@ fhandler_serial::overlapped_setup ()
memset (&io_status, 0, sizeof (io_status));
io_status.hEvent = CreateEvent (&sec_none_nih, TRUE, FALSE, NULL);
ProtectHandle (io_status.hEvent);
overlapped_armed = 0;
}
void __reg3
fhandler_serial::raw_read (void *ptr, size_t& ulen)
{
DWORD io_err, event;
DWORD io_err;
COMSTAT st;
DWORD bytes_to_read, read_bytes, undefined;
DWORD bytes_to_read, read_bytes;
ssize_t tot = 0;
if (ulen > SSIZE_MAX)
@@ -57,11 +56,6 @@ fhandler_serial::raw_read (void *ptr, size_t& ulen)
debug_printf ("ulen %ld, vmin_ %u, vtime_ %u, hEvent %p",
ulen, vmin_, vtime_, io_status.hEvent);
if (!overlapped_armed)
{
SetCommMask (get_handle (), EV_RXCHAR);
ResetEvent (io_status.hEvent);
}
do
{
@@ -93,58 +87,8 @@ fhandler_serial::raw_read (void *ptr, size_t& ulen)
and don't wait. */
if (st.cbInQue && st.cbInQue >= minchars)
bytes_to_read = MIN (st.cbInQue, bytes_to_read);
/* if vtime_ is set, use kernel timeouts, otherwise wait here. */
else if (vtime_ == 0 && !overlapped_armed)
{
if (WaitCommEvent (get_handle (), &event, &io_status))
{
debug_printf ("WaitCommEvent succeeded: event %x", event);
if (!event)
continue;
}
else if (GetLastError () != ERROR_IO_PENDING)
goto err;
overlapped_armed = 1;
}
}
/* overlapped_armed may be set by select, so we have to make sure
to disarm even in O_NONBLOCK mode. */
if (overlapped_armed)
{
switch (cygwait (io_status.hEvent, is_nonblocking () ? 0 : INFINITE))
{
case WAIT_OBJECT_0:
if (!GetOverlappedResult (get_handle (), &io_status,
&undefined, TRUE))
goto err;
debug_printf ("overlapped event %x", event);
break;
case WAIT_SIGNALED:
CancelIo (get_handle ());
overlapped_armed = 0;
if (!GetOverlappedResult (get_handle (), &io_status,
&undefined, TRUE))
goto err;
/* Only if no bytes read, return with EINTR. */
if (!tot)
{
tot = -1;
set_sig_errno (EINTR);
}
goto out;
case WAIT_CANCELED:
CancelIo (get_handle ());
overlapped_armed = 0;
GetOverlappedResult (get_handle (), &io_status, &undefined,
TRUE);
pthread::static_cancel_self ();
/*NOTREACHED*/
default:
goto err;
}
}
overlapped_armed = 0;
ResetEvent (io_status.hEvent);
if (!ReadFile (get_handle (), ptr, bytes_to_read, &read_bytes,
&io_status))
@@ -152,10 +96,50 @@ fhandler_serial::raw_read (void *ptr, size_t& ulen)
if (GetLastError () != ERROR_IO_PENDING)
goto err;
if (is_nonblocking ())
CancelIo (get_handle ());
if (!GetOverlappedResult (get_handle (), &io_status, &read_bytes,
TRUE))
goto err;
{
CancelIo (get_handle ());
if (!GetOverlappedResult (get_handle (), &io_status, &read_bytes,
TRUE))
goto err;
}
else
{
switch (cygwait (io_status.hEvent))
{
default: /* Handle an error case from cygwait basically like
a cancel condition and see if we got "something" */
CancelIo (get_handle ());
/*FALLTHRU*/
case WAIT_OBJECT_0:
if (!GetOverlappedResult (get_handle (), &io_status,
&read_bytes, TRUE))
goto err;
debug_printf ("got %u bytes from ReadFile", read_bytes);
break;
case WAIT_SIGNALED:
CancelIo (get_handle ());
if (!GetOverlappedResult (get_handle (), &io_status,
&read_bytes, TRUE))
goto err;
/* Only if no bytes read, return with EINTR. */
if (!tot && !read_bytes)
{
tot = -1;
set_sig_errno (EINTR);
debug_printf ("signal received, set EINTR");
}
else
debug_printf ("signal received but ignored");
goto out;
case WAIT_CANCELED:
CancelIo (get_handle ());
GetOverlappedResult (get_handle (), &io_status, &read_bytes,
TRUE);
debug_printf ("thread canceled");
pthread::static_cancel_self ();
/*NOTREACHED*/
}
}
}
tot += read_bytes;
ptr = (void *) ((caddr_t) ptr + read_bytes);
@@ -174,9 +158,6 @@ fhandler_serial::raw_read (void *ptr, size_t& ulen)
tot = -1;
__seterrno ();
}
CancelIo (get_handle ());
overlapped_armed = 0;
GetOverlappedResult (get_handle (), &io_status, &undefined, TRUE);
break;
}
}