A crash was observed:
Added loop callback: dbus_watch, 0x560d279e4530
Added loop callback: dbus_watch, 0x560d279e4580
...
Removed loop callback: dbus_watch, 0x560d279e4580
Removed loop callback: dbus_watch, 0x560d279e4530
Aug 31 11:54:11 holaprdel kernel: traps: teamd[557] general protection fault ip:560d26469a55 sp:7ffd43ca9650 error:0 in teamd[560d26463000+16000]
Traceback (from a different run than above):
Core was generated by `/usr/bin/teamd -o -n -U -D -N -t team0 -gg'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00005600ac090a55 in teamd_run_loop_do_callbacks (ctx=0x5600ad9bac70, fds=0x7fff40861250, lcb_list=0x5600ad9bad58) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:321
321 list_for_each_node_entry_safe(lcb, tmp, lcb_list, list) {
(gdb) bt
#0 0x00005600ac090a55 in teamd_run_loop_do_callbacks (ctx=0x5600ad9bac70, fds=0x7fff40861250, lcb_list=0x5600ad9bad58) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:321
#1 teamd_run_loop_run (ctx=0x5600ad9bac70) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:415
#2 0x00005600ac08d8cb in teamd_start (p_ret=<synthetic pointer>, ctx=<optimized out>) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:1557
#3 main (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:1876
(gdb) print *lcb
Cannot access memory at address 0x9dd29944fb7e97fc
(gdb) print *tmp
Cannot access memory at address 0x9dd29944fb7e9804
(gdb)
What has happened is that libdbus called the remove_watch callback twice
in a single go, causing two callbacks being destroyed in one iteration
of teamd_run_loop_do_callbacks()'s list_for_each_node_entry_safe().
This basically turns the _safe() variant of the macro unhelpful, as tmp
points to stale data anyway.
Let's use the unsafe variant then, and terminate the loop once
teamd_loop_callback_del() asks for main loop's attention via
teamd_run_loop_restart(). If there are other callbacks pending an action,
they will get their turn in the next main loop iteration.
Signed-off-by: Lubomir Rintel <lkundrak(a)v3.sk>
---
Changes since v2:
- Break long lines in a comment (comments are apparently hard,
hope it's good this time!).
Changes since v1:
- Fixed formatting of a comment block, reported by checkpatch.pl
teamd/teamd.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/teamd/teamd.c b/teamd/teamd.c
index b310140..a89b702 100644
--- a/teamd/teamd.c
+++ b/teamd/teamd.c
@@ -309,16 +309,28 @@ static void teamd_run_loop_set_fds(struct list_item *lcb_list,
}
}
+static int teamd_check_ctrl(struct teamd_context *ctx)
+{
+ int ctrl_fd = ctx->run_loop.ctrl_pipe_r;
+ struct timeval tv;
+ fd_set rfds;
+
+ FD_ZERO(&rfds);
+ FD_SET(ctrl_fd, &rfds);
+ tv.tv_sec = tv.tv_usec = 0;
+
+ return select(ctrl_fd + 1, &rfds, NULL, NULL, &tv);
+}
+
static int teamd_run_loop_do_callbacks(struct list_item *lcb_list, fd_set *fds,
struct teamd_context *ctx)
{
struct teamd_loop_callback *lcb;
- struct teamd_loop_callback *tmp;
int i;
int events;
int err;
- list_for_each_node_entry_safe(lcb, tmp, lcb_list, list) {
+ list_for_each_node_entry(lcb, lcb_list, list) {
for (i = 0; i < 3; i++) {
if (!(lcb->fd_event & (1 << i)))
continue;
@@ -339,6 +351,16 @@ static int teamd_run_loop_do_callbacks(struct list_item *lcb_list, fd_set *fds,
teamd_log_dbg(ctx, "Failed loop callback: %s, %p",
lcb->name, lcb->priv);
}
+
+ /*
+ * If there's a control byte ready, it's possible that
+ * one or more entries have been removed from the
+ * callback list and restart has been requested. In any
+ * case, let the main loop deal with it first so that
+ * we know we're safe to proceed.
+ */
+ if (teamd_check_ctrl(ctx))
+ return 0;
}
}
return 0;
--
2.37.3
