Messages in this thread Patch in this message | | | Date | Thu, 25 Apr 2019 12:52:33 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [RFC][PATCH 1/2] printk: lock console_sem before we unregister boot consoles |
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On (04/24/19 16:49), Petr Mladek wrote: > > + if (bcon && (newcon->flags & (CON_CONSDEV|CON_BOOT)) == CON_CONSDEV) { > > + console_lock(); > > + /* > > + * We need to iterate through all boot consoles, to make > > * sure we print everything out, before we unregister them. > > */ > > I wondered if moving the console locking could break the above > statement. > > It seems that the comment has been invalid since the commit > 8259cf4342029aad37660e ("printk: Ensure that "console > enabled" messages are printed on the console").
That's very interesting. Yes, you are right, the comment is a leftover. printk used to iterate consoles twice before 8259cf4342029aad37660e
/* we need to iterate through twice, to make sure we print * everything out, before we unregister the console(s) */ printk(KERN_INFO "console handover:"); for_each_console(bcon) printk("boot [%s%d] ", bcon->name, bcon->index);
printk(" -> real [%s%d]\n", newcon->name, newcon->index); for_each_console(bcon) unregister_console(bcon);
But 8259cf4342029aad37660e has changed that and has made comment invalid.
> Could we remove it in this patch? It touches it indirectly anyway.
Sure we can.
We also can take extra care of pr_info("%sconsole [%s%d] enabled\n". Right now we do
... console_unlock(); console_sysfs_notify();
pr_info("%sconsole [%s%d] enabled\n",....
But we can simply move that pr_info() a bit up:
pr_info("%sconsole [%s%d] enabled\n", console_unlock(); console_sysfs_notify();
So the message will be printed on all consoles.
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diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index c2bccf58d03e..981eb6c27cdb 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2813,8 +2813,6 @@ void register_console(struct console *newcon) exclusive_console_stop_seq = console_seq; logbuf_unlock_irqrestore(flags); } - console_unlock(); - console_sysfs_notify(); /* * By unregistering the bootconsoles after we enable the real console @@ -2827,6 +2825,9 @@ void register_console(struct console *newcon) (newcon->flags & CON_BOOT) ? "boot" : "" , newcon->name, newcon->index); + console_unlock(); + console_sysfs_notify(); + if (keep_bootcon) return; --- > Otherwise, the patch looks fine to me: > > Reviewed-by: Petr Mladek <pmladek@suse.com>
Thanks!
-ss
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