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sock/posix: Fix read logic to avoid double-adding socket to pending_recv

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Also write some better comments

Change-Id: I81d59307c5eacc5a71879a83e5040da667909d96
Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/6745
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
This commit is contained in:
Ben Walker 2021-03-04 15:48:36 -07:00 committed by Tomasz Zawadzki
parent 01aa5cb385
commit 8ac5f9e924
1 changed files with 14 additions and 2 deletions
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16
module/sock/posix/posix.c
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@ -885,7 +885,9 @@ posix_sock_recv_from_pipe(struct spdk_posix_sock *sock, struct iovec *diov, int
spdk_pipe_reader_advance(sock->recv_pipe, bytes);
/* If we drained the pipe, take it off the level-triggered list */
/* If we drained the pipe, take it off the pending_recv list. The socket may still have data buffered
* in the kernel to receive, but this will be handled on the next poll call when we get the same EPOLLIN
* event again. */
if (sock->base.group_impl && spdk_pipe_reader_bytes_available(sock->recv_pipe) == 0) {
group = __posix_group_impl(sock->base.group_impl);
TAILQ_REMOVE(&group->pending_recv, sock, link);
@ -908,7 +910,17 @@ posix_sock_read(struct spdk_posix_sock *sock)
bytes = readv(sock->fd, iov, 2);
if (bytes > 0) {
spdk_pipe_writer_advance(sock->recv_pipe, bytes);
if (sock->base.group_impl) {
/* For normal operation, this function is called in response to an EPOLLIN
* event, which already placed the socket onto the pending_recv list.
* But between polls the user may repeatedly call posix_sock_read
* and if they clear the pipe on one of those earlier calls, the
* socket will be removed from the pending_recv list. In that case,
* if we now found more data, put it back on.
* This essentially never happens in practice because the application
* will stop trying to receive and wait for the next EPOLLIN event, but
* for correctness let's handle it. */
if (!sock->pending_recv && sock->base.group_impl) {
group = __posix_group_impl(sock->base.group_impl);
TAILQ_INSERT_TAIL(&group->pending_recv, sock, link);
sock->pending_recv = true;