From: Joe Perches <joe@perches.com>
To: Kay Sievers <kay@vrfy.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
Wu Fengguang <fengguang.wu@intel.com>,
"Paul E. McKenney" <paulmck@us.ibm.com>
Subject: Re: [PATCH v3] printk: Have printk() never buffer its data
Date: Wed, 27 Jun 2012 22:00:14 -0700 [thread overview]
Message-ID: <1340859614.16533.66.camel@joe2Laptop> (raw)
In-Reply-To: <1340869133.876.10.camel@mop>
On Thu, 2012-06-28 at 09:38 +0200, Kay Sievers wrote:
> Here we share the continuation buffer with the console copy logic,
> and partial lines are always immediately flushed to the available
> consoles. They are still buffered internally to improve the
> readability and integrity of the messages and minimize the amount
> of needed record headers to store.
trivia:
> diff --git a/kernel/printk.c b/kernel/printk.c
> @@ -329,8 +337,13 @@ static void log_store(int facility, int level,
> msg->text_len = text_len;
> memcpy(log_dict(msg), dict, dict_len);
> msg->dict_len = dict_len;
> - msg->level = (facility << 3) | (level & 7);
> - msg->ts_nsec = local_clock();
> + msg->facility = facility;
> + msg->level = level & 7;
Doesn't need & 7
> + msg->flags = flags & 0x1f;
> + if (ts_nsec > 0)
> + msg->ts_nsec = ts_nsec;
> + else
> + msg->ts_nsec = local_clock();
Why local_clock? ts_nsec really can be 0.
[]
> @@ -1294,15 +1311,92 @@ static inline void printk_delay(void)
> }
> }
>
> +/*
> + * Continuation lines are buffered, and not committed to the record buffer
> + * until the line is complete, or a race forces it. The line fragments
> + * though, are printed immediately to the consoles to ensure everything has
> + * reached the console in case of a kernel crash.
> + */
> +static struct cont {
> + char buf[LOG_LINE_MAX];
> + size_t len; /* length == 0 means unused buffer */
> + size_t cons; /* bytes written to console */
> + struct task_struct *owner; /* task of first print*/
> + u64 ts_nsec; /* time of first print */
> + u8 level; /* log level of first message */
> + u8 facility; /* log level of first message */
> + bool flushed:1; /* buffer sealed and committed */
bool flushed:1 seems unnecessary.
bool flushed seems more appropriate.
> +} cont;
> +
> +static void cont_flush(void)
> +{
> + if (cont.flushed)
> + return;
> + if (cont.len == 0)
> + return;
> +
> + log_store(cont.facility, cont.level, LOG_NOCONS, cont.ts_nsec,
> + NULL, 0, cont.buf, cont.len);
> +
> + cont.flushed = true;
> +}
> +
> +static bool cont_add(int facility, int level, const char *text, size_t len)
> +{
> + if (cont.len && cont.flushed)
> + return false;
> +
> + if (cont.len + len > sizeof(cont.buf)) {
> + cont_flush();
> + return false;
> + }
> +
> + if (!cont.len) {
> + cont.facility = facility;
> + cont.level = level;
> + cont.owner = current;
> + cont.ts_nsec = local_clock();
> + cont.cons = 0;
> + cont.flushed = false;
> + }
> +
> + memcpy(cont.buf + cont.len, text, len);
Looks like you can still overrun cont.buf.
next prev parent reply other threads:[~2012-06-28 5:00 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-25 19:05 [PATCH v3] printk: Have printk() never buffer its data Steven Rostedt
2012-06-25 22:07 ` Andrew Morton
2012-06-25 23:55 ` Greg Kroah-Hartman
2012-06-26 0:01 ` Linus Torvalds
2012-06-26 0:23 ` Greg Kroah-Hartman
2012-06-26 0:40 ` Linus Torvalds
2012-06-26 0:56 ` Kay Sievers
2012-06-26 1:40 ` Linus Torvalds
2012-06-26 16:07 ` Kay Sievers
2012-06-26 16:30 ` Joe Perches
2012-06-26 16:58 ` Greg Kroah-Hartman
2012-06-26 17:00 ` Kay Sievers
2012-06-26 17:02 ` Greg Kroah-Hartman
2012-06-26 18:34 ` Greg Kroah-Hartman
2012-06-26 18:38 ` Greg Kroah-Hartman
2012-06-26 18:48 ` Greg Kroah-Hartman
2012-06-27 15:13 ` Steven Rostedt
2012-06-27 15:18 ` Steven Rostedt
2012-06-27 15:26 ` Kay Sievers
2012-06-28 7:38 ` Kay Sievers
2012-06-28 1:48 ` Greg Kroah-Hartman
2012-06-28 1:54 ` Steven Rostedt
2012-06-28 2:55 ` Steven Rostedt
2012-06-29 5:30 ` Greg Kroah-Hartman
2012-06-29 11:18 ` Steven Rostedt
2012-06-29 15:40 ` Greg Kroah-Hartman
2012-06-28 5:00 ` Joe Perches [this message]
2012-07-05 7:03 ` Michael Neuling
2012-07-05 8:39 ` Kay Sievers
2012-07-05 8:53 ` Kay Sievers
2012-07-05 10:20 ` Michael Neuling
2012-07-05 11:47 ` Kay Sievers
2012-07-05 12:50 ` Kay Sievers
2012-07-06 0:41 ` Michael Neuling
2012-07-06 0:56 ` Kay Sievers
2012-07-06 3:39 ` Michael Neuling
2012-07-06 3:47 ` Michael Neuling
2012-07-06 10:46 ` Kay Sievers
2012-07-06 15:12 ` Kay Sievers
2012-07-06 21:04 ` Michael Neuling
2012-07-08 17:55 ` Kay Sievers
2012-07-09 17:09 ` Greg Kroah-Hartman
2012-07-09 17:15 ` Joe Perches
2012-07-09 22:36 ` Michael Neuling
2012-07-09 21:42 ` Joe Perches
2012-07-09 22:10 ` Kay Sievers
2012-07-09 22:29 ` Joe Perches
2012-07-09 22:40 ` Kay Sievers
2012-07-09 23:32 ` Joe Perches
2012-07-09 23:41 ` Joe Perches
2012-06-26 0:18 ` Joe Perches
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