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 <bristot@xxxxxxxxxx>
Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
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
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