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printk, tracing: Avoiding unneeded blank lines

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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

Link: http://lkml.kernel.org/r/c350fb2521baaf681a1b4d67981ca0e900108e8e.1467407618.git.bristot@redhat.com

Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: Ingo Molnar <mingo@redhat.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Daniel Bristot de Oliveira 2016-07-01 20:44:37 -03:00 committed by Steven Rostedt
parent 752d596b39
commit 78aebca2c9
1 changed files with 8 additions and 0 deletions
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8
include/trace/events/printk.h
View file

@ -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;
),