On 2025-09-30, Marcos Paulo de Souza <[email protected]> wrote:
> diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
> index
> 558ef31779760340ce42608294d91d5401239f1d..c23abed5933527cb7c6bcc42057fadbb44a43446
> 100644
> --- a/kernel/printk/nbcon.c
> +++ b/kernel/printk/nbcon.c
> @@ -1855,3 +1855,69 @@ void nbcon_device_release(struct console *con)
> console_srcu_read_unlock(cookie);
> }
> EXPORT_SYMBOL_GPL(nbcon_device_release);
> +
> +/**
> + * nbcon_kdb_try_acquire - Try to acquire nbcon console, enter unsafe
> + * section, and initialized nbcon write context
initialize ---^^^^^^^^^^^
And technically it is not initializing the write context, just the
console ownership context. I'm not sure it is really necessary to
mention that.
> + * @con: The nbcon console to acquire
> + * @wctxt: The nbcon write context to be used on success
> + *
> + * Context: Under console_srcu_read_lock() for emiting a single kdb message
emitting ---^^^^^^^
"./scripts/checkpatch.pl --codespell" is your friend. ;-)
> + * using the given con->write_atomic() callback. Can be called
> + * only when the console is usable at the moment.
> + *
> + * Return: True if the console was acquired. False otherwise.
> + *
> + * kdb emits messages on consoles registered for printk() without
> + * storing them into the ring buffer. It has to acquire the console
> + * ownerhip so that it could call con->write_atomic() callback a safe way.
> + *
> + * This function acquires the nbcon console using priority
> NBCON_PRIO_EMERGENCY
> + * and marks it unsafe for handover/takeover.
> + */
> +bool nbcon_kdb_try_acquire(struct console *con,
> + struct nbcon_write_context *wctxt)
> +{
> + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
> +
> + memset(ctxt, 0, sizeof(*ctxt));
> + ctxt->console = con;
> + ctxt->prio = NBCON_PRIO_EMERGENCY;
> +
> + if (!nbcon_context_try_acquire(ctxt, false))
> + return false;
> +
> + if (!nbcon_context_enter_unsafe(ctxt))
> + return false;
> +
> + return true;
> +}
> +
> +/**
> + * nbcon_kdb_release - Exit unsafe section and release the nbcon console
> + *
> + * @wctxt: The nbcon write context initialized by a successful
> + * nbcon_kdb_try_acquire()
> + *
> + * Context: Under console_srcu_read_lock() for emiting a single kdb message
emitting ---^^^^^^^
> + * using the given con->write_atomic() callback. Can be called
> + * only when the console is usable at the moment.
I do not think the "Context" is relevant. It must be called if
a previous call to nbcon_kdb_try_acquire() was successful.
> + */
> +void nbcon_kdb_release(struct nbcon_write_context *wctxt)
> +{
> + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
> +
> + if (!nbcon_context_exit_unsafe(ctxt))
> + return;
> +
> + nbcon_context_release(ctxt);
> +
> + /*
> + * Flush any new printk() messages added when the console was blocked.
> + * Only the console used by the given write context was blocked.
> + * The console was locked only when the write_atomic() callback
> + * was usable.
> + */
> + __nbcon_atomic_flush_pending_con(ctxt->console,
> + prb_next_reserve_seq(prb), false);
This can all be one line. 100 characters is the official limit for code.
> +}
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