From: Steven Rostedt <rostedt@goodmis.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [RFC/PATCH] ftrace: Allow to change size of function graph filters
Date: Fri, 13 Jan 2017 23:50:01 -0500 [thread overview]
Message-ID: <20170113235001.6f92fb28@vmware.local.home> (raw)
In-Reply-To: <20170114042000.GA1735@danjae.aot.lge.com>
On Sat, 14 Jan 2017 13:20:00 +0900
Namhyung Kim <namhyung@kernel.org> wrote:
> But I'm not sure how to synchronize hash table manipulations. It
> seems synchronize_sched() is not good enough for function graph
> tracer, right? So I limited changing filter size only when no tracer
> is used, but is it ok to have the limitation when adding or removing
> an entry to/from the table? If not, what can I do?
There's already a hash that function tracing uses. Look at the code in
ftrace_hash_move(). If you make it where the hash is always looked at
with preemption disabled, you can use synchronize_sched() to modify the
hash.
The trampolines are a bit trickier, because there's no way to disable
preemption or do any other synchronization when they are called.
-- Steve
prev parent reply other threads:[~2017-01-14 4:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-13 4:22 [RFC/PATCH] ftrace: Allow to change size of function graph filters Namhyung Kim
2017-01-13 16:16 ` Steven Rostedt
2017-01-14 4:20 ` Namhyung Kim
2017-01-14 4:50 ` Steven Rostedt [this message]
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