The initial intention of the UML kmsg_dumper is to dump the kernel
buffers to stdout if there is no console available to perform the
regular crash output.
However, if ttynull was registered as a console, no crash output was
seen. Commit e23fe90dec28 ("um: kmsg_dumper: always dump when not tty
console") tried to fix this by performing the kmsg_dump unless the
stdio console was behind /dev/console or enabled. But this allowed
kmsg dumping to occur even if other non-stdio consoles will output
the crash output. Also, a console being the driver behind
/dev/console has nothing to do with a crash scenario.
Restore the initial intention by dumping the kernel buffers to stdout
only if a non-ttynull console is registered and enabled. Also add
detailed comments so that it is clear why these rules are applied.
Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
---
arch/um/kernel/kmsg_dump.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
index 0224fcb36e22..40abf1e9ccb1 100644
--- a/arch/um/kernel/kmsg_dump.c
+++ b/arch/um/kernel/kmsg_dump.c
@@ -17,13 +17,22 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
unsigned long flags;
size_t len = 0;
- /* only dump kmsg when no console is available */
+ /*
+ * If no consoles are available to output crash information, dump
+ * the kmsg buffer to stdout.
+ */
+
if (!console_trylock())
return;
for_each_console(con) {
- if(strcmp(con->name, "tty") == 0 &&
- (con->flags & (CON_ENABLED | CON_CONSDEV)) != 0) {
+ /*
+ * The ttynull console and disabled consoles are ignored
+ * since they cannot output. All other consoles are
+ * expected to output the crash information.
+ */
+ if (strcmp(con->name, "ttynull") != 0 &&
+ (con->flags & CON_ENABLED)) {
break;
}
}
--
2.30.2