| Date | Tue, 25 Oct 2022 17:35:08 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH printk v2 30/38] printk: console_device: use srcu console list iterator |
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On Wed 2022-10-19 17:01:52, John Ogness wrote: > Use srcu console list iteration for console list traversal. > > Document why the console_lock is still necessary. > > Signed-off-by: John Ogness <john.ogness@linutronix.de> > --- > kernel/printk/printk.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > index e478cb92e7ba..410ad9d5649c 100644 > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -3025,15 +3025,24 @@ struct tty_driver *console_device(int *index) > { > struct console *c; > struct tty_driver *driver = NULL; > + int cookie; > > + /* > + * Stop console printing because the device() callback may > + * assume the console is not within its write() callback.
Again, I would like to know more details about the possible races with the write() callback. It is not that obvious.
> + */ > console_lock(); > - for_each_console(c) { > + > + cookie = console_srcu_read_lock(); > + for_each_console_srcu(c) { > if (!c->device) > continue; > driver = c->device(c, index); > if (driver) > break; > } > + console_srcu_read_unlock(cookie); > + > console_unlock(); > return driver;
Otherwise, the change looks good.
Best Regards, Petr
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