[PATCH 4/4] printk, tracing: Avoiding unneeded blank lines

[Daniel Bristot de Oliveira]

Printk messages often finish with '\n' to cause a new line.
But as each tracepoint is already printed in a new line,
printk messages that finish with '\n' ends up adding a blank
line to the trace output. For example:

 kworker/0:1-86[000] d...46.006949: console: [   46.006946] usb 
1-3: USB disconnect, device number 3

 kworker/2:2-374   [002] d...48.699342: console: [   48.699339] usb 
1-3: new high-speed USB device number 4 using ehci-pci

 kworker/2:2-374   [002] d...49.041450: console: [   49.041448] usb 
1-3: New USB device found, idVendor=5986, idProduct=0

To avoid unneeded blank lines, this patch checks if the printk
message finishes with '\n', if so, it cut is off the '\n' to
avoid blank lines.

In a patched kernel, the same messages are printed without
extra blank lines. For example:

 kworker/0:4-185   [000] d...23.641738: console: [   23.641736] usb 
1-3: USB disconnect, device number 3
 kworker/0:4-185   [000] d...24.918703: console: [   24.918700] usb 
1-3: new high-speed USB device number 4 using ehci-pci
 kworker/0:4-185   [000] d...25.228308: console: [   25.228306] usb 
1-3: New USB device found, idVendor=5986, idProduct=02d5


Signed-off-by: Daniel Bristot de Oliveira 
Reviewed-by: Steven Rostedt 
Cc: Steven Rostedt 
Cc: Ingo Molnar 
Cc: linux-kernel@vger.kernel.org
---
 include/trace/events/printk.h | 8 
 1 file changed, 8 insertions(+)

diff --git a/include/trace/events/printk.h b/include/trace/events/printk.h
index 542a755..bc9139d29 100644
--- a/include/trace/events/printk.h
+++ b/include/trace/events/printk.h
@@ -16,6 +16,14 @@ TRACE_EVENT(console,
),
 
TP_fast_assign(
+   /*
+* Each trace entry is printed in a new line.
+* If the msg finishes with '\n', cut it off
+* to avoid blank lines in the trace.
+*/
+   if ((len > 0) && (text[len-1] == '\n'))
+   len -= 1;
+
memcpy(__get_str(msg), text, len);
__get_str(msg)[len] = 0;
),
-- 
2.7.4

[PATCH 4/4] printk, tracing: Avoiding unneeded blank lines

[Daniel Bristot de Oliveira]

Printk messages often finish with '\n' to cause a new line.
But as each tracepoint is already printed in a new line,
printk messages that finish with '\n' ends up adding a blank
line to the trace output. For example:

 kworker/0:1-86[000] d...46.006949: console: [   46.006946] usb 
1-3: USB disconnect, device number 3

 kworker/2:2-374   [002] d...48.699342: console: [   48.699339] usb 
1-3: new high-speed USB device number 4 using ehci-pci

 kworker/2:2-374   [002] d...49.041450: console: [   49.041448] usb 
1-3: New USB device found, idVendor=5986, idProduct=0

To avoid unneeded blank lines, this patch checks if the printk
message finishes with '\n', if so, it cut is off the '\n' to
avoid blank lines.

In a patched kernel, the same messages are printed without
extra blank lines. For example:

 kworker/0:4-185   [000] d...23.641738: console: [   23.641736] usb 
1-3: USB disconnect, device number 3
 kworker/0:4-185   [000] d...24.918703: console: [   24.918700] usb 
1-3: new high-speed USB device number 4 using ehci-pci
 kworker/0:4-185   [000] d...25.228308: console: [   25.228306] usb 
1-3: New USB device found, idVendor=5986, idProduct=02d5


Signed-off-by: Daniel Bristot de Oliveira 
Reviewed-by: Steven Rostedt 
Cc: Steven Rostedt 
Cc: Ingo Molnar 
Cc: linux-kernel@vger.kernel.org
---
 include/trace/events/printk.h | 8 
 1 file changed, 8 insertions(+)

diff --git a/include/trace/events/printk.h b/include/trace/events/printk.h
index 542a755..bc9139d29 100644
--- a/include/trace/events/printk.h
+++ b/include/trace/events/printk.h
@@ -16,6 +16,14 @@ TRACE_EVENT(console,
),
 
TP_fast_assign(
+   /*
+* Each trace entry is printed in a new line.
+* If the msg finishes with '\n', cut it off
+* to avoid blank lines in the trace.
+*/
+   if ((len > 0) && (text[len-1] == '\n'))
+   len -= 1;
+
memcpy(__get_str(msg), text, len);
__get_str(msg)[len] = 0;
),
-- 
2.7.4