[lxc-devel] [lxc/master] terminal: remove sigwinch command

[brauner on Github]

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From 2bd158cc0c79da7d48e36306d41b5677ec976fc6 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Thu, 13 Dec 2018 15:44:36 +0100
Subject: [PATCH] terminal: remove sigwinch command

SIGWINCH is handled in lxc_terminal_signalfd_cb().

I cannot for the life of me figure out what this is supposed to do.
Afaict, it scans a global list that is totally unnecessary and also
let's say you have 100 ttys and for a single one SIGWINCH is sent. In
that case the whole list is walked and two ioctl()s are performed: one
to get window size one to set window size. For 99 of them the window
size hasn't changed.
If we see issues we can revert!

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 src/lxc/commands.c | 18 +++---------------
 src/lxc/terminal.c | 36 +-----------------------------------
 src/lxc/terminal.h |  6 ------
 3 files changed, 4 insertions(+), 56 deletions(-)

diff --git a/src/lxc/commands.c b/src/lxc/commands.c
index 133384d72..392fdab2c 100644
--- a/src/lxc/commands.c
+++ b/src/lxc/commands.c
@@ -665,7 +665,7 @@ static int lxc_cmd_stop_callback(int fd, struct lxc_cmd_req *req,
 }
 
 /*
- * lxc_cmd_terminal_winch: To process as if a SIGWINCH were received
+ * lxc_cmd_terminal_winch: noop
  *
  * @name      : name of container to connect to
  * @lxcpath   : the lxcpath in which the container is running
@@ -674,26 +674,14 @@ static int lxc_cmd_stop_callback(int fd, struct lxc_cmd_req *req,
  */
 int lxc_cmd_terminal_winch(const char *name, const char *lxcpath)
 {
-	int ret, stopped;
-	struct lxc_cmd_rr cmd = {
-		.req = { .cmd = LXC_CMD_TERMINAL_WINCH },
-	};
-
-	ret = lxc_cmd(name, &cmd, &stopped, lxcpath, NULL);
-	if (ret < 0)
-		return ret;
-
 	return 0;
 }
 
 static int lxc_cmd_terminal_winch_callback(int fd, struct lxc_cmd_req *req,
 					   struct lxc_handler *handler)
 {
-	struct lxc_cmd_rsp rsp = { .data = 0 };
-
-	lxc_terminal_sigwinch(SIGWINCH);
-
-	return lxc_cmd_rsp_send(fd, &rsp);
+	/* should never be called */
+	return -1;
 }
 
 /*
diff --git a/src/lxc/terminal.c b/src/lxc/terminal.c
index 4060e7f9b..de0089101 100644
--- a/src/lxc/terminal.c
+++ b/src/lxc/terminal.c
@@ -59,15 +59,6 @@
 
 lxc_log_define(terminal, lxc);
 
-static struct lxc_list lxc_ttys;
-
-typedef void (*sighandler_t)(int);
-
-__attribute__((constructor)) void lxc_terminal_init_global(void)
-{
-	lxc_list_init(&lxc_ttys);
-}
-
 void lxc_terminal_winsz(int srcfd, int dstfd)
 {
 	int ret;
@@ -95,20 +86,6 @@ void lxc_terminal_winsz(int srcfd, int dstfd)
 static void lxc_terminal_winch(struct lxc_terminal_state *ts)
 {
 	lxc_terminal_winsz(ts->stdinfd, ts->masterfd);
-
-	if (ts->winch_proxy)
-		lxc_cmd_terminal_winch(ts->winch_proxy, ts->winch_proxy_lxcpath);
-}
-
-void lxc_terminal_sigwinch(int sig)
-{
-	struct lxc_list *it;
-	struct lxc_terminal_state *ts;
-
-	lxc_list_for_each(it, &lxc_ttys) {
-		ts = it->elem;
-		lxc_terminal_winch(ts);
-	}
 }
 
 int lxc_terminal_signalfd_cb(int fd, uint32_t events, void *cbdata,
@@ -161,9 +138,6 @@ struct lxc_terminal_state *lxc_terminal_signal_init(int srcfd, int dstfd)
 	if (!istty) {
 		INFO("fd %d does not refer to a tty device", srcfd);
 	} else {
-		/* Add tty to list to be scanned at SIGWINCH time. */
-		lxc_list_add_elem(&ts->node, ts);
-		lxc_list_add_tail(&lxc_ttys, &ts->node);
 		ret = sigaddset(&mask, SIGWINCH);
 		if (ret < 0)
 			SYSNOTICE("Failed to add SIGWINCH to signal set");
@@ -199,9 +173,6 @@ struct lxc_terminal_state *lxc_terminal_signal_init(int srcfd, int dstfd)
 		ts->sigfd = -1;
 	}
 
-	if (istty)
-		lxc_list_del(&ts->node);
-
 	return ts;
 }
 
@@ -214,9 +185,6 @@ void lxc_terminal_signal_fini(struct lxc_terminal_state *ts)
 			SYSWARN("Failed to restore signal mask");
 	}
 
-	if (isatty(ts->stdinfd))
-		lxc_list_del(&ts->node);
-
 	free(ts);
 }
 
@@ -1065,14 +1033,12 @@ int lxc_console(struct lxc_container *c, int ttynum,
 		goto close_fds;
 	}
 	ts->escape = escape;
-	ts->winch_proxy = c->name;
-	ts->winch_proxy_lxcpath = c->config_path;
 	ts->stdoutfd = stdoutfd;
 
 	istty = isatty(stdinfd);
 	if (istty) {
 		lxc_terminal_winsz(stdinfd, masterfd);
-		lxc_cmd_terminal_winch(ts->winch_proxy, ts->winch_proxy_lxcpath);
+		lxc_terminal_winsz(ts->stdinfd, ts->masterfd);
 	} else {
 		INFO("File descriptor %d does not refer to a terminal", stdinfd);
 	}
diff --git a/src/lxc/terminal.h b/src/lxc/terminal.h
index bfd271f44..02f31f8d8 100644
--- a/src/lxc/terminal.h
+++ b/src/lxc/terminal.h
@@ -68,12 +68,6 @@ struct lxc_terminal_state {
 	 */
 	int saw_escape;
 
-	/* Name of the container to forward the SIGWINCH event to. */
-	const char *winch_proxy;
-
-	/* Path of the container to forward the SIGWINCH event to. */
-	const char *winch_proxy_lxcpath;
-
 	/* File descriptor that accepts signals. If set to -1 no signal handler
 	 * could be installed. This also means that the sigset_t oldmask member
 	 * is meaningless.