From: Anders Roxell <anders.roxell@linaro.org>
To: rostedt@goodmis.org, mingo@redhat.com, catalin.marinas@arm.com,
will.deacon@arm.com
Cc: keescook@chromium.org, arnd@arndb.de,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Anders Roxell <anders.roxell@linaro.org>
Subject: [PATCH v3] tracing: add cond_resched to ftrace_replace_code()
Date: Tue, 4 Dec 2018 20:40:44 +0100 [thread overview]
Message-ID: <20181204194044.9506-1-anders.roxell@linaro.org> (raw)
When running in qemu on an kernel built with allmodconfig and debug
options (in particular kcov and ubsan) enabled, ftrace_replace_code
function call take minutes. The ftrace selftest calls
ftrace_replace_code to look >40000 through
ftrace_make_call/ftrace_make_nop, and these end up calling
__aarch64_insn_write/aarch64_insn_patch_text_nosync.
Microseconds add up because this is called in a loop for each dyn_ftrace
record, and this triggers the softlockup watchdog unless we let it sleep
occasionally.
Rework so that we call cond_resched() if !irqs_disabled() && !preempt_count().
Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
kernel/trace/ftrace.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c375e33239f7..7c9f49a5a1ab 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2419,11 +2419,19 @@ void __weak ftrace_replace_code(int enable)
{
struct dyn_ftrace *rec;
struct ftrace_page *pg;
+ bool schedulable;
int failed;
if (unlikely(ftrace_disabled))
return;
+ /*
+ * Some archs call this function with interrupts or preemption
+ * disabled. However, for other archs that can preempt, this can cause
+ * an tremendous unneeded latency.
+ */
+ schedulable = !irqs_disabled() && !preempt_count();
+
do_for_each_ftrace_rec(pg, rec) {
if (rec->flags & FTRACE_FL_DISABLED)
@@ -2435,6 +2443,8 @@ void __weak ftrace_replace_code(int enable)
/* Stop processing */
return;
}
+ if (schedulable)
+ cond_resched();
} while_for_each_ftrace_rec();
}
--
2.19.2
next reply other threads:[~2018-12-04 19:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-04 19:40 Anders Roxell [this message]
2018-12-04 22:32 ` [PATCH v3] tracing: add cond_resched to ftrace_replace_code() Steven Rostedt
2018-12-05 10:50 ` Anders Roxell
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=20181204194044.9506-1-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).