linux-kernel - Re: [RFC PATCH 2/5] sysrq: use pr_cont

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Date:   Thu, 20 Aug 2020 10:48:40 -0700
From:   Joe Perches <joe@...ches.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        John Ogness <john.ogness@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/5] sysrq: use pr_cont_t for cont messages

On Wed, 2020-08-19 at 18:03 -0700, Linus Torvalds wrote:
> On Wed, Aug 19, 2020 at 4:26 PM John Ogness <john.ogness@...utronix.de> wrote:
> > Use the new pr_cont_t mechanism.
> 
> This looks actively much worse than the old code.

Isn't this just a generic mechanism to simplify
the accumulation of
logging message chunks?

It does seem straightforward enough to me.

And here it seems like the 'for (j =...)' loop is superfluous.

Maybe something like this would be reasonable:
---
 drivers/tty/sysrq.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index a8e39b2cdd55..a145e4fc1a2a 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -572,21 +572,14 @@ void __handle_sysrq(int key, bool check_mask)
 			console_loglevel = orig_log_level;
 		}
 	} else {
-		pr_info("HELP : ");
-		/* Only print the help msg once per handler */
+		pr_context c;
+		pr_info_start(&c, "HELP :");
 		for (i = 0; i < ARRAY_SIZE(sysrq_key_table); i++) {
-			if (sysrq_key_table[i]) {
-				int j;
-
-				for (j = 0; sysrq_key_table[i] !=
-						sysrq_key_table[j]; j++)
-					;
-				if (j != i)
-					continue;
-				pr_cont("%s ", sysrq_key_table[i]->help_msg);
-			}
+			if (!sysrq_key_table[i])
+				continue;
+			pr_next(&c, " %s", sysrq_key_table[i]->help_msg);
 		}
-		pr_cont("\n");
+		pr_end(&c, "\n");
 		console_loglevel = orig_log_level;
 	}
 	rcu_read_unlock();