blktrace: disable kill option - take 2

Fixup for 513950.

Problem:
'blktrace -d <device> -k' does not kill a running
backgound trace. Executing 'blktrace -d <device> -k'
for the second time results in "BLKTRACETEARDOWN:
Invalid argument" message and then each run of
blktrace on that machine prints the following output:
BLKTRACESETUP: No such file or directory.

The bug:
The option -k results in clobbering information
about running trace by kernel (blk_trace_remove),
while resources (files open in debugfs by the running
background blktrace) are not released.

Solution:
Update documentation:
Undocument the non-working "kill" option. Advise
to send SIGINT signall via kill(1) to the running
background blktrace for its correct termination.

Signed-off-by: Edward Shishkin <edward@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/blktrace.c b/blktrace.c
index 660ad7a..b9f9b68 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -442,7 +442,6 @@ static char usage_str[] = \
 	"\t-r Path to mounted debugfs, defaults to /sys/kernel/debug\n" \
 	"\t-o File(s) to send output to\n" \
 	"\t-D Directory to prepend to output file names\n" \
-	"\t-k Kill a running trace\n" \
 	"\t-w Stop after defined time, in seconds\n" \
 	"\t-a Only trace specified actions. See documentation\n" \
 	"\t-A Give trace mask as a single value. See documentation\n" \