From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Petr Mladek <pmladek@suse.com>,
John Ogness <john.ogness@linutronix.de>,
Andrea Parri <andrea.parri@amarulasolutions.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Brendan Higgins <brendanhiggins@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v4 0/9] printk: new ringbuffer implementation
Date: Fri, 6 Sep 2019 22:44:39 +0900 [thread overview]
Message-ID: <20190906134439.GA9590@tigerII.localdomain> (raw)
In-Reply-To: <20190906104948.GX2349@hirez.programming.kicks-ass.net>
On (09/06/19 12:49), Peter Zijlstra wrote:
> On Fri, Sep 06, 2019 at 07:09:43PM +0900, Sergey Senozhatsky wrote:
>
> > ---
> > diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
> > index 139c310049b1..9c73eb6259ce 100644
> > --- a/kernel/printk/printk_safe.c
> > +++ b/kernel/printk/printk_safe.c
> > @@ -103,7 +103,10 @@ static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s,
> > if (atomic_cmpxchg(&s->len, len, len + add) != len)
> > goto again;
> >
> > - queue_flush_work(s);
> > + if (early_console)
> > + early_console->write(early_console, s->buffer + len, add);
> > + else
> > + queue_flush_work(s);
> > return add;
> > }
>
> You've not been following along, that generates absolutely unreadable
> garbage.
This was more of a joke/reference to "Those NMI buffers are a trainwreck
and need to die a horrible death". Of course this needs a re-entrant cpu
lock to serialize access to atomic/early consoles. But here is one more
missing thing - we need atomic/early consoles on a separate, sort of
immutable, list. And probably forbid any modifications of such console
drivers, (PM, etc.) If we can do this then we don't need to take console_sem
while we iterate that list, which removes sched/timekeeping locks out
of the fast printk() path.
We, at the same time, don't have that many options on systems without
atomic/early consoles. Move printing to NMI (e.g. up to X pending logbug
lines per NMI)? Move printing to IPI (again, up to X pending logbuf lines
per IPI)? printk() softirqs?
-ss
next prev parent reply other threads:[~2019-09-06 13:44 UTC|newest]
Thread overview: 131+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 22:26 [RFC PATCH v4 0/9] printk: new ringbuffer implementation John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 1/9] printk-rb: add a new printk " John Ogness
2019-08-20 8:15 ` numlist_pop(): " Petr Mladek
2019-08-21 5:41 ` John Ogness
2019-09-04 12:19 ` Peter Zijlstra
2019-08-20 8:22 ` assign_desc() barriers: " Petr Mladek
2019-08-20 14:14 ` Petr Mladek
2019-08-21 5:52 ` John Ogness
2019-08-22 11:53 ` Petr Mladek
2019-08-25 2:06 ` John Ogness
2019-08-26 8:21 ` John Ogness
2019-08-20 8:55 ` comments style: " Petr Mladek
2019-08-20 9:27 ` Sergey Senozhatsky
2019-08-21 5:46 ` John Ogness
2019-08-22 13:50 ` Petr Mladek
2019-08-22 17:38 ` Andrea Parri
2019-08-23 10:47 ` Petr Mladek
2019-08-23 14:27 ` Andrea Parri
2019-08-23 9:49 ` Sergey Senozhatsky
2019-08-23 5:54 ` Sergey Senozhatsky
2019-08-23 10:29 ` Petr Mladek
2019-08-21 5:42 ` John Ogness
2019-08-22 12:44 ` Petr Mladek
2019-08-20 13:50 ` dataring_push() barriers " Petr Mladek
2019-08-25 2:42 ` John Ogness
2019-08-27 14:36 ` Petr Mladek
2019-08-28 13:43 ` John Ogness
2019-08-20 15:12 ` datablock reuse races " Petr Mladek
2019-08-23 9:21 ` numlist_push() barriers " Petr Mladek
2019-08-26 8:34 ` Andrea Parri
2019-08-26 8:43 ` Andrea Parri
2019-08-26 14:10 ` Petr Mladek
2019-08-26 16:01 ` Andrea Parri
2019-08-26 22:36 ` John Ogness
2019-08-27 7:40 ` Petr Mladek
2019-08-27 14:28 ` John Ogness
2019-08-27 15:07 ` Petr Mladek
2019-08-28 10:24 ` John Ogness
2019-08-23 17:18 ` numlist API " Petr Mladek
2019-08-26 23:57 ` John Ogness
2019-08-27 13:03 ` Petr Mladek
2019-08-28 7:13 ` John Ogness
2019-08-28 8:58 ` Petr Mladek
2019-08-28 14:03 ` John Ogness
2019-08-29 11:28 ` Petr Mladek
2019-09-03 7:58 ` Sergey Senozhatsky
2019-08-30 14:48 ` dataring " Petr Mladek
2019-08-07 22:26 ` [RFC PATCH v4 2/9] printk-rb: add test module John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 3/9] printk-rb: fix missing includes/exports John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 4/9] printk-rb: initialize new descriptors as invalid John Ogness
2019-08-20 9:23 ` Petr Mladek
2019-08-20 10:16 ` Sergey Senozhatsky
2019-08-21 5:56 ` John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 5/9] printk-rb: remove extra data buffer size allocation John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 6/9] printk-rb: adjust test module ringbuffer sizes John Ogness
2019-08-19 21:29 ` [PATCH] printk-rb: fix test module macro usage John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 7/9] printk-rb: increase size of seq and size variables John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 8/9] printk-rb: new functionality to support printk John Ogness
2019-08-20 9:59 ` Sergey Senozhatsky
2019-08-21 5:47 ` John Ogness
2019-08-07 22:26 ` [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation John Ogness
2019-08-08 19:07 ` Linus Torvalds
2019-08-08 22:55 ` John Ogness
2019-08-08 23:33 ` Linus Torvalds
2019-08-08 23:45 ` Steven Rostedt
2019-08-09 0:21 ` Linus Torvalds
2019-08-09 0:48 ` Steven Rostedt
2019-08-09 1:15 ` Linus Torvalds
2019-08-09 11:15 ` Thomas Gleixner
2019-08-09 16:00 ` Linus Torvalds
2019-08-09 20:07 ` Thomas Gleixner
2019-08-09 20:20 ` Linus Torvalds
2019-08-09 6:14 ` Peter Zijlstra
2019-08-09 7:08 ` John Ogness
2019-08-09 15:57 ` Linus Torvalds
2019-08-10 5:53 ` Thomas Gleixner
2019-09-10 3:19 ` Sergey Senozhatsky
2019-08-12 9:54 ` Geert Uytterhoeven
2019-08-16 5:46 ` Dave Young
2019-08-16 5:54 ` Dave Young
2019-08-16 9:40 ` John Ogness
2019-09-04 12:35 ` [RFC PATCH v4 0/9] printk: " Peter Zijlstra
2019-09-05 13:05 ` Petr Mladek
2019-09-05 14:31 ` Peter Zijlstra
2019-09-05 15:38 ` Thomas Gleixner
2019-09-05 16:11 ` Steven Rostedt
2019-09-05 21:10 ` John Ogness
2019-09-06 9:39 ` Petr Mladek
2019-09-09 14:11 ` printk meeting at LPC Thomas Gleixner
2019-09-13 13:26 ` John Ogness
2019-09-13 14:48 ` Daniel Vetter
2019-09-15 13:47 ` John Ogness
2019-09-16 8:44 ` Daniel Vetter
2019-09-16 4:30 ` Tetsuo Handa
2019-09-16 10:46 ` Petr Mladek
2019-09-16 13:43 ` Steven Rostedt
2019-09-16 14:28 ` John Ogness
2019-09-17 8:11 ` Petr Mladek
2019-09-17 7:52 ` Petr Mladek
2019-09-17 13:02 ` Steven Rostedt
2019-09-17 13:12 ` Greg Kroah-Hartman
2019-09-17 13:37 ` Steven Rostedt
2019-09-17 14:08 ` Tetsuo Handa
2019-09-17 7:51 ` Sergey Senozhatsky
2019-09-18 1:25 ` Sergey Senozhatsky
2019-09-18 2:08 ` Steven Rostedt
2019-09-18 2:36 ` Sergey Senozhatsky
2019-09-18 5:19 ` Sergey Senozhatsky
2019-09-18 7:42 ` John Ogness
2019-09-18 8:10 ` Sergey Senozhatsky
2019-09-18 9:05 ` John Ogness
2019-09-18 9:11 ` Sergey Senozhatsky
2019-09-18 16:41 ` Petr Mladek
2019-09-18 16:48 ` Steven Rostedt
2019-09-24 14:24 ` Petr Mladek
2019-09-19 8:06 ` Daniel Vetter
2019-09-18 7:33 ` John Ogness
2019-09-18 8:08 ` Sergey Senozhatsky
2019-10-04 14:48 ` Tony Asleson
2019-10-07 12:01 ` Petr Mladek
2019-09-06 9:06 ` [RFC PATCH v4 0/9] printk: new ringbuffer implementation Peter Zijlstra
2019-09-06 10:09 ` Sergey Senozhatsky
2019-09-06 10:49 ` Peter Zijlstra
2019-09-06 13:44 ` Sergey Senozhatsky [this message]
2019-09-06 12:42 ` Petr Mladek
2019-09-06 14:01 ` Peter Zijlstra
2019-09-06 14:22 ` Peter Zijlstra
2019-09-06 19:53 ` Sergey Senozhatsky
2019-09-06 22:47 ` John Ogness
2019-09-08 22:18 ` Peter Zijlstra
2019-09-10 3:22 ` Sergey Senozhatsky
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