linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Anders Roxell <anders.roxell@linaro.org>
To: rostedt@goodmis.org, mingo@redhat.com
Cc: keescook@chromium.org, catalin.marinas@arm.com,
	will.deacon@arm.com, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Anders Roxell <anders.roxell@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH 2/3] tracing: instruct KCOV not to track tracing files
Date: Fri, 30 Nov 2018 16:09:35 +0100	[thread overview]
Message-ID: <20181130150935.27493-1-anders.roxell@linaro.org> (raw)

When we have KCOV enabled and running ftrace startup tests we end up in
a softlockup. Kcov and ftrace tracing each other makes it really slow:

[  275.141388] Testing tracer wakeup_dl:  PASSED
[  304.738345] Testing tracer function_graph:
[  716.236822] watchdog: BUG: soft lockup - CPU#0 stuck for 21s! [ksoftirqd/0:9]

Rework so that we don't let KCOV look at tracing files. Could probably
be more selective here, but in in general letting KCOV and ftrace check
each isn't the best idea.

Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 kernel/trace/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index f81dadbc7c4a..c7c73b976103 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -6,6 +6,11 @@ ifdef CONFIG_FUNCTION_TRACER
 ORIG_CFLAGS := $(KBUILD_CFLAGS)
 KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
 
+# If instrumentation of this dir is enabled, the function tracer gets really
+# slow. Probably could be more selective here, but note that files related
+# to tracing.shouldn't be traced anyway.
+KCOV_INSTRUMENT		:= n
+
 ifdef CONFIG_FTRACE_SELFTEST
 # selftest needs instrumentation
 CFLAGS_trace_selftest_dynamic.o = $(CC_FLAGS_FTRACE)
-- 
2.19.2


             reply	other threads:[~2018-11-30 15:09 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-30 15:09 Anders Roxell [this message]
2018-11-30 15:22 ` [PATCH 2/3] tracing: instruct KCOV not to track tracing files Steven Rostedt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181130150935.27493-1-anders.roxell@linaro.org \
    --to=anders.roxell@linaro.org \
    --cc=arnd@arndb.de \
    --cc=catalin.marinas@arm.com \
    --cc=keescook@chromium.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=rostedt@goodmis.org \
    --cc=will.deacon@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).