Messages in this thread | | | Date | Fri, 11 Jan 2019 11:24:09 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] sysrq: Restore original console_loglevel when sysrq disabled |
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On Fri, 11 Jan 2019 22:07:29 +0900 Sergey Senozhatsky <sergey.senozhatsky@gmail.com> wrote:
> On (01/11/19 13:45), Petr Mladek wrote: > > The sysrq header line is printed with an increased loglevel > > to provide users some positive feedback. > > > > The original loglevel is not restored when the sysrq operation > > is disabled. This bug was introduced in 2.6.12 (pre-git-history) > > by the commit ("Allow admin to enable only some of the Magic-Sysrq > > functions"). > > > Good find, and the patch looks OK to me. A small comment below. > FWIW, > Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > > > --- > > A side note (nitpick, etc.); it's Friday night in here, I'm enjoying > my beer; so maybe I'm wrong about the whole thing. > > > > @@ -553,6 +553,7 @@ void __handle_sysrq(int key, bool check_mask) > > op_p->handler(key); > > } else { > > pr_cont("This sysrq operation is disabled.\n"); > > + console_loglevel = orig_log_level; > > } > > This looks a bit racy. > > When we do > > printk("FOO\n"); > console_loglevel = XYZ; > > We don't have any real guarantees that printk("FOO\n") will print > anything straight ahead. It is possible that console_sem is already > locked and the owner is preempted, so by the time the console_sem > owner picks up that FOO\n messages, console_loglevel is back to > orig_log_level and suppress_message_printing() will just tell us > to skip the message. > > Do we need pr_cont() there? Maybe we can just have a normal pr_err() > which would always tell that "key" sysrq is disabled? (we also > would need to change the error message a bit). >
All this is for another patch and another discussion. This current patch keeps with what is there and fixes a missing reset of console_loglevel.
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-- Steve
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