2013-04-21 00:10:19 +00:00
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From c7e9b2a5b981209f4e77b26562758663cc060900 Mon Sep 17 00:00:00 2001
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2013-02-20 01:14:18 +00:00
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From: Amit Shah <amit.shah@redhat.com>
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Date: Mon, 21 Mar 2011 22:00:27 +0100
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Subject: [PATCH] char: Update send_all() to handle nonblocking chardev write
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requests
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The send_all function is modified to return to the caller in case the
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driver cannot handle any more data. It returns -EAGAIN or
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WSAEWOULDBLOCK on non-Windows and Windows platforms respectively. This
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is only done when the caller sets a callback function handler indicating
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it's not interested in blocking till the driver has written out all the
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data.
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Currently there's no driver or caller that supports this. Future
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commits will add such capability.
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Signed-off-by: Amit Shah <amit.shah@redhat.com>
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Signed-off-by: Cole Robinson <crobinso@redhat.com>
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---
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include/qemu/sockets.h | 3 ++-
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qemu-char.c | 69 +++++++++++++++++++++++++++++++++++++++++++++-----
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2 files changed, 65 insertions(+), 7 deletions(-)
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diff --git a/include/qemu/sockets.h b/include/qemu/sockets.h
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2013-04-21 00:10:19 +00:00
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index 0ccf32f..42ca690 100644
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2013-02-20 01:14:18 +00:00
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--- a/include/qemu/sockets.h
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+++ b/include/qemu/sockets.h
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@@ -29,6 +29,7 @@ int inet_aton(const char *cp, struct in_addr *ia);
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#include "qemu/option.h"
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#include "qapi/error.h"
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#include "qapi/qmp/qerror.h"
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+#include "char/char.h"
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/* misc helpers */
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int qemu_socket(int domain, int type, int protocol);
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@@ -36,7 +37,7 @@ int qemu_accept(int s, struct sockaddr *addr, socklen_t *addrlen);
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int socket_set_cork(int fd, int v);
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2013-04-21 00:10:19 +00:00
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void qemu_set_block(int fd);
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void qemu_set_nonblock(int fd);
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2013-02-20 01:14:18 +00:00
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-int send_all(int fd, const void *buf, int len1);
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+int send_all(CharDriverState *chr, int fd, const void *buf, int len1);
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/* callback function for nonblocking connect
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* valid fd on success, negative error code on failure
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diff --git a/qemu-char.c b/qemu-char.c
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2013-04-21 00:10:19 +00:00
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index ab0c552..96fc54e 100644
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2013-02-20 01:14:18 +00:00
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--- a/qemu-char.c
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+++ b/qemu-char.c
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@@ -508,7 +508,7 @@ static CharDriverState *qemu_chr_open_mux(CharDriverState *drv)
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#ifdef _WIN32
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-int send_all(int fd, const void *buf, int len1)
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+static int do_send(int fd, const void *buf, int len1, bool nonblock)
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{
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int ret, len;
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@@ -516,9 +516,14 @@ int send_all(int fd, const void *buf, int len1)
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while (len > 0) {
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ret = send(fd, buf, len, 0);
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if (ret < 0) {
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+ if (nonblock && len1 - len) {
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+ return len1 - len;
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+ }
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errno = WSAGetLastError();
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if (errno != WSAEWOULDBLOCK) {
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return -1;
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+ } else if (errno == WSAEWOULDBLOCK && nonblock) {
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+ return WSAEWOULDBLOCK;
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}
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} else if (ret == 0) {
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break;
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@@ -532,7 +537,7 @@ int send_all(int fd, const void *buf, int len1)
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#else
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-int send_all(int fd, const void *_buf, int len1)
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+static int do_send(int fd, const void *_buf, int len1, bool nonblock)
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{
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int ret, len;
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const uint8_t *buf = _buf;
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@@ -541,8 +546,15 @@ int send_all(int fd, const void *_buf, int len1)
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while (len > 0) {
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ret = write(fd, buf, len);
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if (ret < 0) {
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- if (errno != EINTR && errno != EAGAIN)
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+ if (nonblock && len1 - len) {
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+ return len1 - len;
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+ }
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+ if (errno == EAGAIN && nonblock) {
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+ return -EAGAIN;
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+ }
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+ if (errno != EINTR && errno != EAGAIN) {
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return -1;
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+ }
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} else if (ret == 0) {
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break;
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} else {
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@@ -557,6 +569,44 @@ int send_all(int fd, const void *_buf, int len1)
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#define STDIO_MAX_CLIENTS 1
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static int stdio_nb_clients;
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+int send_all(CharDriverState *chr, int fd, const void *_buf, int len1)
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+{
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+ int ret, eagain_errno;
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+ bool nonblock;
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+
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+ if (chr && chr->write_blocked) {
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+ /*
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+ * The caller should not send us data while we're blocked,
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+ * but this can happen when multiple writers are woken at once,
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+ * so simply return -EAGAIN.
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+ */
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+ return -EAGAIN;
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+ }
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+
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+ nonblock = false;
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+ /*
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+ * Ensure the char backend is able to receive and handle the
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+ * 'write unblocked' event before we turn on nonblock support.
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+ */
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+ if (chr && chr->chr_enable_write_fd_handler && chr->chr_write_unblocked) {
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+ nonblock = true;
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+ }
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+ ret = do_send(fd, _buf, len1, nonblock);
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+
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+#ifdef _WIN32
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+ eagain_errno = WSAEWOULDBLOCK;
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+#else
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+ eagain_errno = -EAGAIN;
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+#endif
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+
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+ if (nonblock && (ret == eagain_errno || (ret >= 0 && ret < len1))) {
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+ /* Update fd handler to wake up when chr becomes writable */
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+ chr->chr_enable_write_fd_handler(chr);
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+ chr->write_blocked = true;
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+ }
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+ return ret;
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+}
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+
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#ifndef _WIN32
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typedef struct {
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@@ -568,7 +618,7 @@ typedef struct {
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static int fd_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
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{
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FDCharDriver *s = chr->opaque;
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- return send_all(s->fd_out, buf, len);
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+ return send_all(chr, s->fd_out, buf, len);
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}
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static int fd_chr_read_poll(void *opaque)
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@@ -893,7 +943,7 @@ static int pty_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
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pty_chr_update_read_handler(chr);
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return 0;
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}
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- return send_all(s->fd, buf, len);
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+ return send_all(chr, s->fd, buf, len);
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}
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static int pty_chr_read_poll(void *opaque)
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@@ -2188,8 +2238,15 @@ static void tcp_closed(void *opaque)
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static int tcp_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
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{
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TCPCharDriver *s = chr->opaque;
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+
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if (s->connected) {
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- return send_all(s->fd, buf, len);
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+ int ret;
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+
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+ ret = send_all(chr, s->fd, buf, len);
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+ if (ret == -1 && errno == EPIPE) {
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+ tcp_closed(chr);
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+ }
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+ return ret;
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} else {
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/* XXX: indicate an error ? */
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return len;
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