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authorLinus Torvalds <torvalds@linux-foundation.org>2016-10-06 11:48:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-10-06 11:48:41 -0700
commit95107b30be68953e3a4f1c3994c2233500502ccf (patch)
treeed1824ce842d9813f2ee8a5fa8683e0d6b13f662 /scripts
parent541efb7632642cab55361178d73d544f025b593c (diff)
parenta0d0c6216afad4b2b1704a72bd76bea259e07655 (diff)
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Merge tag 'trace-v4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt: "This release cycle is rather small. Just a few fixes to tracing. The big change is the addition of the hwlat tracer. It not only detects SMIs, but also other latency that's caused by the hardware. I have detected some latency from large boxes having bus contention" * tag 'trace-v4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Call traceoff trigger after event is recorded ftrace/scripts: Add helper script to bisect function tracing problem functions tracing: Have max_latency be defined for HWLAT_TRACER as well tracing: Add NMI tracing in hwlat detector tracing: Have hwlat trace migrate across tracing_cpumask CPUs tracing: Add documentation for hwlat_detector tracer tracing: Added hardware latency tracer ftrace: Access ret_stack->subtime only in the function profiler function_graph: Handle TRACE_BPUTS in print_graph_comment tracing/uprobe: Drop isdigit() check in create_trace_uprobe
Diffstat (limited to 'scripts')
-rwxr-xr-xscripts/tracing/ftrace-bisect.sh115
1 files changed, 115 insertions, 0 deletions
diff --git a/scripts/tracing/ftrace-bisect.sh b/scripts/tracing/ftrace-bisect.sh
new file mode 100755
index 000000000000..9ff8ac5fc53c
--- /dev/null
+++ b/scripts/tracing/ftrace-bisect.sh
@@ -0,0 +1,115 @@
+#!/bin/bash
+#
+# Here's how to use this:
+#
+# This script is used to help find functions that are being traced by function
+# tracer or function graph tracing that causes the machine to reboot, hang, or
+# crash. Here's the steps to take.
+#
+# First, determine if function tracing is working with a single function:
+#
+# (note, if this is a problem with function_graph tracing, then simply
+# replace "function" with "function_graph" in the following steps).
+#
+# # cd /sys/kernel/debug/tracing
+# # echo schedule > set_ftrace_filter
+# # echo function > current_tracer
+#
+# If this works, then we know that something is being traced that shouldn't be.
+#
+# # echo nop > current_tracer
+#
+# # cat available_filter_functions > ~/full-file
+# # ftrace-bisect ~/full-file ~/test-file ~/non-test-file
+# # cat ~/test-file > set_ftrace_filter
+#
+# *** Note *** this will take several minutes. Setting multiple functions is
+# an O(n^2) operation, and we are dealing with thousands of functions. So go
+# have coffee, talk with your coworkers, read facebook. And eventually, this
+# operation will end.
+#
+# # echo function > current_tracer
+#
+# If it crashes, we know that ~/test-file has a bad function.
+#
+# Reboot back to test kernel.
+#
+# # cd /sys/kernel/debug/tracing
+# # mv ~/test-file ~/full-file
+#
+# If it didn't crash.
+#
+# # echo nop > current_tracer
+# # mv ~/non-test-file ~/full-file
+#
+# Get rid of the other test file from previous run (or save them off somewhere).
+# # rm -f ~/test-file ~/non-test-file
+#
+# And start again:
+#
+# # ftrace-bisect ~/full-file ~/test-file ~/non-test-file
+#
+# The good thing is, because this cuts the number of functions in ~/test-file
+# by half, the cat of it into set_ftrace_filter takes half as long each
+# iteration, so don't talk so much at the water cooler the second time.
+#
+# Eventually, if you did this correctly, you will get down to the problem
+# function, and all we need to do is to notrace it.
+#
+# The way to figure out if the problem function is bad, just do:
+#
+# # echo <problem-function> > set_ftrace_notrace
+# # echo > set_ftrace_filter
+# # echo function > current_tracer
+#
+# And if it doesn't crash, we are done.
+#
+# If it does crash, do this again (there's more than one problem function)
+# but you need to echo the problem function(s) into set_ftrace_notrace before
+# enabling function tracing in the above steps. Or if you can compile the
+# kernel, annotate the problem functions with "notrace" and start again.
+#
+
+
+if [ $# -ne 3 ]; then
+ echo 'usage: ftrace-bisect full-file test-file non-test-file'
+ exit
+fi
+
+full=$1
+test=$2
+nontest=$3
+
+x=`cat $full | wc -l`
+if [ $x -eq 1 ]; then
+ echo "There's only one function left, must be the bad one"
+ cat $full
+ exit 0
+fi
+
+let x=$x/2
+let y=$x+1
+
+if [ ! -f $full ]; then
+ echo "$full does not exist"
+ exit 1
+fi
+
+if [ -f $test ]; then
+ echo -n "$test exists, delete it? [y/N]"
+ read a
+ if [ "$a" != "y" -a "$a" != "Y" ]; then
+ exit 1
+ fi
+fi
+
+if [ -f $nontest ]; then
+ echo -n "$nontest exists, delete it? [y/N]"
+ read a
+ if [ "$a" != "y" -a "$a" != "Y" ]; then
+ exit 1
+ fi
+fi
+
+sed -ne "1,${x}p" $full > $test
+sed -ne "$y,\$p" $full > $nontest