Messages in this thread | | | Date | Wed, 22 May 2024 17:18:13 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH v6 1/2] printk: Add function to replay kernel log on consoles |
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On Wed 2024-03-13 15:50:52, Sreenath Vijayan wrote: > Add a generic function console_replay_all() for replaying > the kernel log on consoles, in any context. It would allow > viewing the logs on an unresponsive terminal via sysrq. > > Reuse the existing code from console_flush_on_panic() for > resetting the sequence numbers, by introducing a new helper > function __console_rewind_all(). It is safe to be called > under console_lock(). > > Try to acquire lock on the console subsystem without waiting. > If successful, reset the sequence number to oldest available > record on all consoles and call console_unlock() which will > automatically flush the messages to the consoles. > > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -4259,6 +4271,23 @@ void kmsg_dump_rewind(struct kmsg_dump_iter *iter) > } > EXPORT_SYMBOL_GPL(kmsg_dump_rewind); > > +/** > + * console_replay_all - replay kernel log on consoles
It should rather be called "console_try_replay_all()" to make it clear that it is just the best effort.
> + * > + * Try to obtain lock on console subsystem and replay all > + * available records in printk buffer on the consoles. > + * Does nothing if lock is not obtained. > + * > + * Context: Any context.
This should be:
* Context: Any, except for NMI
Basically only lockless code is safe in NMI which is not the case here.
> + */ > +void console_replay_all(void) > +{ > + if (console_trylock()) { > + __console_rewind_all(); > + /* Consoles are flushed as part of console_unlock(). */ > + console_unlock(); > + } > +} > #endif
Otherwise, it looks good. With the two changes:
Reviewed-by: Petr Mladek <pmladek@suse.com>
I am sorry for the late review. I have been snowed under tasks. Also I had healthy problems.
I have seen a mail that Greg has queued the patch in tty-next. I am not sure if it still can be fixed. It will be perfectly fine to change this by a followup patch.
Best Regards, Petr
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