[PATCH] printk: Optimize if statement logic where newline exists

[PATCH] printk: Optimize if statement logic where newline exists

[Steven Rostedt]

In reviewing Kay's fix up patch: "printk: Have printk() never buffer its
data", I found two if statements that could be combined and optimized.

Put together the two 'cont.len && cont.owner == current' if statements
into a single one, and check if we need to call cont_add(). This also
removes the unneeded double cont_flush() calls.

Link: http://lkml.kernel.org/r/1340869133.876.10.camel@mop

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---

[ This patch is dependent on Kay's patch, referenced at the above Link ]

Index: linux-trace.git/kernel/printk.c
===================================================================
--- linux-trace.git.orig/kernel/printk.c
+++ linux-trace.git/kernel/printk.c
@@ -1474,15 +1474,14 @@ asmlinkage int vprintk_emit(int facility
 		bool stored = false;
 
 		/*
-		 * Flush the conflicting buffer. An earlier newline was missing,
-		 * or we race with a continuation line from an interrupt.
+		 * If an earlier newline was missing and it was the same task,
+		 * either merge it with the current buffer and flush, or if
+		 * there was a race with interrupts (prefix == true) then just
+		 * flush it out and store this line separately.
 		 */
-		if (cont.len && prefix && cont.owner == current)
-			cont_flush();
-
-		/* Merge with our buffer if possible; flush it in any case */
 		if (cont.len && cont.owner == current) {
-			stored = cont_add(facility, level, text, text_len);
+			if (!prefix)
+				stored = cont_add(facility, level, text, text_len);
 			cont_flush();
 		}
 

Re: [PATCH] printk: Optimize if statement logic where newline exists

[Steven Rostedt]

On Fri, 2012-06-29 at 11:40 -0400, Steven Rostedt wrote:
> In reviewing Kay's fix up patch: "printk: Have printk() never buffer its
> data", I found two if statements that could be combined and optimized.
> 
> Put together the two 'cont.len && cont.owner == current' if statements
> into a single one, and check if we need to call cont_add(). This also
> removes the unneeded double cont_flush() calls.
> 
> Link: http://lkml.kernel.org/r/1340869133.876.10.camel@mop
> 
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> 
> [ This patch is dependent on Kay's patch, referenced at the above Link ]
> 

As the above link seems to time out, here's a more direct one:


http://marc.info/?l=linux-kernel&m=134084777330388

-- Steve