| Message ID | 20221107141638.3790965-7-john.ogness@linutronix.de |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | reduce console_lock scope | expand |
On Mon 2022-11-07 15:22:04, John Ogness wrote: > 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 <john.ogness@linutronix.de> The change makes sense to me: Reviewed-by: Petr Mladek <pmladek@suse.com> Best Regards, Petr
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; } }
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 <john.ogness@linutronix.de> --- arch/um/kernel/kmsg_dump.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)