From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: John Ogness <john.ogness@linutronix.de>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH printk 3/5] printk: use buffer pool for sprint buffers
Date: Thu, 24 Sep 2020 10:54:45 +0200 [thread overview]
Message-ID: <20200924085445.GK6442@alley> (raw)
In-Reply-To: <20200924061746.GF577@jagdpanzerIV.localdomain>
On Thu 2020-09-24 15:17:46, Sergey Senozhatsky wrote:
> On (20/09/22 17:44), John Ogness wrote:
> > +/*
> > + * The sprint buffers are used with interrupts disabled, so each CPU
> > + * only requires 2 buffers: for non-NMI and NMI contexts. Recursive
> > + * printk() calls are handled by the safe buffers.
> > + */
> > +#define SPRINT_CTX_DEPTH 2
> > +
> > +/* Static sprint buffers for early boot (only 1 CPU). */
> > +static DECLARE_BITMAP(sprint_static_textbuf_map, SPRINT_CTX_DEPTH);
> > +static char sprint_static_textbuf[SPRINT_CTX_DEPTH * LOG_LINE_MAX];
> > +
> > +/* Dynamically allocated sprint buffers. */
> > +static unsigned int sprint_dynamic_textbuf_count;
> > +static unsigned long *sprint_dynamic_textbuf_map;
> > +static char *sprint_dynamic_textbuf;
>
> Just a question:
>
> Can dynamic_textbuf be a PER_CPU array of five textbuf[1024] buffers
> (for normal printk, nmi, hard irq, soft irq and one extra buffer for
> recursive printk calls)?
That would be my preferred fallback when the approach with
vsprintf(NULL, ) is not acceptable for some reasons.
But I still think that calling vsprintf(NULL, ) is the most trivial
and good enough solution.
IMHO, the solution with per-CPU buffers is not that trivial, for
example:
What if recursive printk() is interrupted by NMI and it causes
yet another recursion?
Is one level of recursion enough?
Best Regards,
Petr
next prev parent reply other threads:[~2020-09-24 8:54 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 15:38 [PATCH printk 0/5] printk: remove logbuf_lock John Ogness
2020-09-22 15:38 ` [PATCH printk 1/5] printk: get new seq before enabling interrupts John Ogness
2020-09-23 14:17 ` Petr Mladek
2020-09-23 14:36 ` John Ogness
2020-09-22 15:38 ` [PATCH printk 2/5] printk: kmsg_dump_rewind_nolock: start from first record John Ogness
2020-09-23 14:52 ` Petr Mladek
2020-09-23 15:39 ` John Ogness
2020-09-22 15:38 ` [PATCH printk 3/5] printk: use buffer pool for sprint buffers John Ogness
2020-09-23 15:11 ` Petr Mladek
2020-09-23 15:21 ` David Laight
2020-09-23 16:41 ` Petr Mladek
2020-09-24 5:40 ` Sergey Senozhatsky
2020-09-24 8:45 ` Petr Mladek
2020-09-24 8:53 ` Sergey Senozhatsky
2020-09-24 9:49 ` Rasmus Villemoes
2020-09-25 8:15 ` Petr Mladek
2020-09-24 9:54 ` Rasmus Villemoes
2020-09-24 12:32 ` Rasmus Villemoes
2020-09-25 8:28 ` Petr Mladek
2020-09-30 8:06 ` Rasmus Villemoes
2020-09-30 8:51 ` Petr Mladek
2020-09-30 8:57 ` John Ogness
2020-09-30 13:35 ` Steven Rostedt
2020-09-30 14:32 ` David Laight
2020-10-01 7:15 ` Rasmus Villemoes
2020-10-01 7:58 ` Petr Mladek
2020-09-24 1:21 ` Sergey Senozhatsky
2020-09-24 6:17 ` Sergey Senozhatsky
2020-09-24 8:54 ` Petr Mladek [this message]
2020-09-24 9:06 ` Sergey Senozhatsky
2020-09-25 8:13 ` Petr Mladek
2020-09-22 15:38 ` [PATCH printk 4/5] printk: remove logbuf_lock, add syslog_lock John Ogness
2020-09-23 16:30 ` Petr Mladek
2020-09-24 8:45 ` Sergey Senozhatsky
2020-09-24 9:21 ` John Ogness
2020-09-22 15:38 ` [PATCH printk 5/5] printk: remove nmi safe buffers John Ogness
2020-09-23 16:36 ` Petr Mladek
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