This implements locking around the blocking call to ReadFile to get
around a Windows kernel bug where a blocking ReadFile operation on a
stream can deadlock the thread. This allows uv_read_stop to immediately
cancel a pending IO operation, and allows uv_pipe_getsockname to
"pause" any pending read (from libuv) while it retrieves the
sockname information.
If unsupported by the OS (pre-Vista), this reverts to the old
(e.g. deadlock-prone) behavior
Closes#1313
The unix and windows process implementations diverge in their behavior
when dealing with subprocesses that are spawned with a relative path.
With unix the *child's* PATH environment variable is read, whereas
with windows the *parent's* environment variable is read.
This commit brings the two implementation in line with respect to
their behavior of reading PATH by having both read the *child's* PATH
environment variable. This involves looking into the user-provided
environment on windows and extracting the PATH variable specifically
so it can be inspected later on.
This is the libuv side of the fix for Node's cluster module on Windows.
https://github.com/joyent/node/issues/7691
Windows and Unix return certain socket errors (i.e. EADDRINUSE) at
different times: bind on Windows, and listen on Unix.
In an effort to hide this difference, libuv on Windows stores such
errors in the bind_error field of uv_tcp_t, to defer raising it at
listen time.
This worked fine except for the case in which a socket is shared in
a Node cluster and a bind error occurs.
A previous attempt to fix this (
d1e6be14603da36fe00e
) was flawed becaused in an attempt to relay the error at the JS level
it caused the master to start accepting connections.
With this new approach, libuv itself is relaying the bind errors,
providing for a uniform behavior of uv_tcp_listen.
If libuv is loaded as a DLL and is later unloaded deadlocks can happen
when running atexit handlers, so we can't use synchronization
priomitives or join threads there.
For reference see https://github.com/saghul/pyuv/issues/171
After 41891222bc landed it's possible that uv__udp_sendmsg is called
even if there are no pending write nor write completed requests:
1. User calls uv_udp_send and the request is sent immediately. The
request is the added to the completed queue and we 'feed' the uv__io
handle so that we process the completed request in the next
iteration.
2. User calls uv_udp_send again but the request is not completed
immediately, so it's queued in the write_queue.
3. The uv__io handle gets a UV__POLLOUT event and uv__udp_sendmsg is
run, which completes the send request and puts it in the
write_completed_queue. Afterwards, uv__udp_run_completed is executed
and the write_completed queue is drained.
4. At this point, the uv__io handle was made pending in step 3, in
uv__udp_sendmsg, but we no longer have requests to write or to complete,
so we skip processing.
It's possible that recv_cb_called is bigger than the number of sockets,
because if all sends succeed the recv callback is called twice: once
with the actual data, and another time with 0.
This makes libuv more tolerant to the properties of the pipes
that it can use without any issue. This is necessary because Cygwin
(and hence Mintty) opens STDIN without FILE_WRITE_ATTRIBUTES.
This functionality is present in stream and uv_udp_t has a queue
as well so it makes sense for udp to have a send_write_size.
Since udp sends entire messages atomically, the send_queue_count field
lets the user determine how many messages are there left to send.
