From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin-developers@cygwin.com
Subject: Re: 3.3.0: Possible regression in cygwin DLL (Win10); fixed in snapshot
Date: Wed, 10 Nov 2021 17:30:03 +0900 [thread overview]
Message-ID: <20211110173003.88359e8482ffa8b8be326903@nifty.ne.jp> (raw)
In-Reply-To: <YYZqNiBRTfYWwFev@calimero.vinschen.de>
[-- Attachment #1: Type: text/plain, Size: 1500 bytes --]
Hi Corinna,
On Sat, 6 Nov 2021 12:42:46 +0100
Corinna Vinschen wrote:
> On Nov 6 15:10, Takashi Yano wrote:
> > Unfortunately, these solutions do not resolve the issue
> > which is another issue with C# program:
> > https://cygwin.com/pipermail/cygwin/2021-March/247987.html
> > This still needs FILE_SYNCHRONOUS_IO_NONALERT flag.
>
> If we want to add FILE_SYNCHRONOUS_IO_NONALERT, this would have to be
> solved by running NtReadFile/NtWriteFile synchronously in a thread,
> started on every invocation of raw_read/raw_write. raw_read/raw_write
> would then call cygwait on the thread object. To break on signal or
> thread cancallation events, it would have to call CancelSynchronousIo.
> That's certainly doable.
I tried to implement your idea, however, I noticed that
NtQueryObject(ObjectNameInformation) call in
get_query_hdl_per_process() is blocked while reading the
pipe if FIPE_SYNCHRONOUS_IO_NONALERT is set and pipe is
in blocking mode.
So I would like to propose alternative implementation with
FILE_SYNCHRONOUS_IO_NONALERT being set. Please have a look
at attached patch. With this patch, pipe itself in read side
is always set to nonblocking mode and simulate the blocking
behaviour in raw_read(). This can eliminate creating thread
for reading as well as calling CancelSynchronousIo().
Note that setting FILE_SYNCHRONOUS_IO_NONALERT only for read
pipe seems to be enough for C# programs.
What do you think of this implementation?
--
Takashi Yano <takashi.yano@nifty.ne.jp>
[-- Attachment #2: pipe20211110.patch --]
[-- Type: application/octet-stream, Size: 5801 bytes --]
diff --git a/winsup/cygwin/fhandler_pipe.cc b/winsup/cygwin/fhandler_pipe.cc
index 13731437e..41121394e 100644
--- a/winsup/cygwin/fhandler_pipe.cc
+++ b/winsup/cygwin/fhandler_pipe.cc
@@ -90,7 +90,10 @@ fhandler_pipe::init (HANDLE f, DWORD a, mode_t mode, int64_t uniq_id)
set_ino (uniq_id);
set_unique_id (uniq_id | !!(mode & GENERIC_WRITE));
if (opened_properly)
- set_pipe_non_blocking (is_nonblocking ());
+ /* Set read pipe always nonblocking to allow signal handling
+ even with FILE_SYNCHRONOUS_IO_NONALERT. */
+ set_pipe_non_blocking (get_device () == FH_PIPER ?
+ true : is_nonblocking ());
return 1;
}
@@ -264,9 +267,9 @@ fhandler_pipe::release_select_sem (const char *from)
if (get_dev () == FH_PIPER) /* Number of select() and writer */
n_release = get_obj_handle_count (select_sem)
- get_obj_handle_count (read_mtx);
- else /* Number of select() call */
+ else /* Number of select() call and reader */
n_release = get_obj_handle_count (select_sem)
- - get_obj_handle_count (hdl_cnt_mtx);
+ - get_obj_handle_count (get_handle ());
debug_printf("%s(%s) release %d", from,
get_dev () == FH_PIPER ? "PIPER" : "PIPEW", n_release);
if (n_release)
@@ -279,19 +282,10 @@ fhandler_pipe::raw_read (void *ptr, size_t& len)
size_t nbytes = 0;
NTSTATUS status = STATUS_SUCCESS;
IO_STATUS_BLOCK io;
- HANDLE evt = NULL;
if (!len)
return;
- /* Create a wait event if we're in blocking mode. */
- if (!is_nonblocking () && !(evt = CreateEvent (NULL, false, false, NULL)))
- {
- __seterrno ();
- len = (size_t) -1;
- return;
- }
-
DWORD timeout = is_nonblocking () ? 0 : INFINITE;
DWORD waitret = cygwait (read_mtx, timeout);
switch (waitret)
@@ -319,48 +313,23 @@ fhandler_pipe::raw_read (void *ptr, size_t& len)
{
ULONG_PTR nbytes_now = 0;
ULONG len1 = (ULONG) (len - nbytes);
- waitret = WAIT_OBJECT_0;
- if (evt)
- ResetEvent (evt);
FILE_PIPE_LOCAL_INFORMATION fpli;
status = NtQueryInformationFile (get_handle (), &io,
&fpli, sizeof (fpli),
FilePipeLocalInformation);
if (NT_SUCCESS (status))
{
- if (fpli.ReadDataAvailable == 0 && nbytes != 0)
- break;
+ if (fpli.ReadDataAvailable == 0 && nbytes != 0)
+ break;
}
else if (nbytes != 0)
break;
- status = NtReadFile (get_handle (), evt, NULL, NULL, &io, ptr,
+ status = NtReadFile (get_handle (), NULL, NULL, NULL, &io, ptr,
len1, NULL, NULL);
- if (evt && status == STATUS_PENDING)
- {
- waitret = cygwait (evt, INFINITE, cw_cancel | cw_sig);
- /* If io.Status is STATUS_CANCELLED after CancelIo, IO has actually
- been cancelled and io.Information contains the number of bytes
- processed so far.
- Otherwise IO has been finished regulary and io.Status contains
- valid success or error information. */
- CancelIo (get_handle ());
- if (waitret == WAIT_SIGNALED && io.Status != STATUS_CANCELLED)
- waitret = WAIT_OBJECT_0;
-
- if (waitret == WAIT_CANCELED)
- status = STATUS_THREAD_CANCELED;
- else if (waitret == WAIT_SIGNALED)
- status = STATUS_THREAD_SIGNALED;
- else
- status = io.Status;
- }
if (isclosed ()) /* A signal handler might have closed the fd. */
{
- if (waitret == WAIT_OBJECT_0)
- set_errno (EBADF);
- else
- __seterrno ();
+ set_errno (EBADF);
nbytes = (size_t) -1;
}
else if (NT_SUCCESS (status)
@@ -393,7 +362,16 @@ fhandler_pipe::raw_read (void *ptr, size_t& len)
nbytes = (size_t) -1;
break;
}
- fallthrough;
+ waitret = cygwait (select_sem, 1);
+ if (waitret == WAIT_CANCELED)
+ pthread::static_cancel_self ();
+ else if (waitret == WAIT_SIGNALED)
+ {
+ set_errno (EINTR);
+ nbytes = (size_t) -1;
+ break;
+ }
+ continue;
default:
__seterrno_from_nt_status (status);
nbytes = (size_t) -1;
@@ -406,8 +384,6 @@ fhandler_pipe::raw_read (void *ptr, size_t& len)
break;
}
ReleaseMutex (read_mtx);
- if (evt)
- CloseHandle (evt);
if (status == STATUS_THREAD_SIGNALED && nbytes == 0)
{
set_errno (EINTR);
@@ -993,9 +969,12 @@ nt_create (LPSECURITY_ATTRIBUTES sa_ptr, HANDLE &r, HANDLE &w,
npfsh, sa_ptr->lpSecurityDescriptor);
timeout.QuadPart = -500000;
+ /* Set FILE_SYNCHRONOUS_IO_NONALERT flag so that native
+ C# programs work with cygwin pipe. */
status = NtCreateNamedPipeFile (&r, access, &attr, &io,
FILE_SHARE_READ | FILE_SHARE_WRITE,
- FILE_CREATE, 0, pipe_type,
+ FILE_CREATE,
+ FILE_SYNCHRONOUS_IO_NONALERT, pipe_type,
FILE_PIPE_BYTE_STREAM_MODE,
0, 1, psize, psize, &timeout);
@@ -1107,7 +1086,9 @@ fhandler_pipe::fcntl (int cmd, intptr_t arg)
const bool was_nonblocking = is_nonblocking ();
int res = fhandler_base::fcntl (cmd, arg);
const bool now_nonblocking = is_nonblocking ();
- if (now_nonblocking != was_nonblocking)
+ /* Do not set blocking mode for read pipe to allow signal handling
+ even with FILE_SYNCHRONOUS_IO_NONALERT. */
+ if (now_nonblocking != was_nonblocking && get_device () != FH_PIPER)
set_pipe_non_blocking (now_nonblocking);
return res;
}
diff --git a/winsup/cygwin/globals.cc b/winsup/cygwin/globals.cc
index 48fb312de..ac5ad0307 100644
--- a/winsup/cygwin/globals.cc
+++ b/winsup/cygwin/globals.cc
@@ -69,7 +69,7 @@ int NO_COPY dynamically_loaded;
/* Some CYGWIN environment variable variables. */
bool allow_glob = true;
bool ignore_case_with_glob;
-bool pipe_byte;
+bool pipe_byte = true; /* Default to byte mode so that C# programs work. */
bool reset_com;
bool wincmdln;
winsym_t allow_winsymlinks = WSYM_default;
next prev parent reply other threads:[~2021-11-10 8:30 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAEv6GOB8PXHgHoz7hdJy6Bia2GWEmUDnTd252gTGinz2vuv=hA@mail.gmail.com>
[not found] ` <20211105123950.b118a7f2ba38379764df4c12@nifty.ne.jp>
[not found] ` <CAEv6GOA-y58YrftXgEgFrjqtOTHmfdu2Vrq76Lwn0suZpZ=U9w@mail.gmail.com>
[not found] ` <20211105170542.96ce6dd4ca32880ddfddd660@nifty.ne.jp>
[not found] ` <CAEv6GODiM88Xfhk9R3AcEW6UTYSzACzYe4C0gPoTYm=u9ZTqRQ@mail.gmail.com>
[not found] ` <20211106044116.698b465a5d8ed6ce2cc75c99@nifty.ne.jp>
[not found] ` <2cfa5de7-3b95-9062-4572-f36d304bc916@cornell.edu>
2021-11-06 6:10 ` Takashi Yano
2021-11-06 11:42 ` Corinna Vinschen
2021-11-06 12:02 ` Corinna Vinschen
2021-11-06 14:13 ` Takashi Yano
2021-11-06 17:20 ` Corinna Vinschen
2021-11-07 3:01 ` Takashi Yano
2021-11-06 16:38 ` Ken Brown
2021-11-06 17:20 ` Corinna Vinschen
2021-11-07 3:46 ` Takashi Yano
2021-11-07 22:20 ` Ken Brown
2021-11-08 8:23 ` Takashi Yano
2021-11-08 9:46 ` Corinna Vinschen
2021-11-10 8:30 ` Takashi Yano [this message]
2021-11-10 10:34 ` Corinna Vinschen
2021-11-10 13:30 ` Takashi Yano
2021-11-10 20:35 ` Corinna Vinschen
2021-11-10 21:32 ` Ken Brown
2021-11-11 16:11 ` Ken Brown
2021-11-12 8:38 ` Takashi Yano
2021-11-16 23:46 ` Takashi Yano
2021-11-17 8:10 ` Takashi Yano
2021-11-17 15:12 ` Ken Brown
2021-11-11 9:52 ` Corinna Vinschen
2021-11-11 11:12 ` Takashi Yano
2021-11-11 11:33 ` Corinna Vinschen
2021-11-11 12:02 ` Takashi Yano
2021-11-11 13:20 ` Takashi Yano
2021-11-11 16:07 ` Corinna Vinschen
2021-11-12 8:33 ` Takashi Yano
2021-11-12 10:02 ` Corinna Vinschen
2021-12-12 13:26 ` Takashi Yano
2021-12-12 13:36 ` Ken Brown
2021-12-13 11:15 ` Takashi Yano
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