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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	paulmck <paulmck@kernel.org>, Stefan Metzmacher <metze@samba.org>,
	stable <stable@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/3] Fix: tracepoint: static call: compare data on transition from 2->1 callees
Date: Thu, 5 Aug 2021 13:57:30 -0400 (EDT)	[thread overview]
Message-ID: <1270289445.7118.1628186250992.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20210805130700.0bc7e52a@oasis.local.home>

----- On Aug 5, 2021, at 1:07 PM, rostedt rostedt@goodmis.org wrote:

> On Thu,  5 Aug 2021 09:27:15 -0400
> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
> 
>> On transition from 2->1 callees, we should be comparing .data rather
>> than .func, because the same callback can be registered twice with
>> different data, and what we care about here is that the data of array
>> element 0 is unchanged to skip rcu sync.
>> 
>> Link:
>> https://lore.kernel.org/io-uring/4ebea8f0-58c9-e571-fd30-0ce4f6f09c70@samba.org/
> 
> FYI, You only need to show one Fixes.
> 
>> Fixes: d25e37d89dd2 ("tracepoint: Optimize using static_call()")
> 
> The above is fixed by the one below. Which means all the stable kernels
> that have the above, will also have the below, and thus the above is
> just redundant.
> 
>> Fixes: 547305a64632 ("tracepoint: Fix out of sync data passing by static
>> caller")
> 
> The above is what the patch actually fixes.
> 
>> Fixes: 352384d5c84e ("tracepoints: Update static_call before tp_funcs when
>> adding a tracepoint")
> 
> How does this patch fix the above? Perhaps the above did not go enough
> to fix the issue, but it's unrelated.

OK

> 
> I'll remove the first and last Fixes tag.

OK

> 
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>> Cc: Steven Rostedt <rostedt@goodmis.org>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: "Paul E. McKenney" <paulmck@kernel.org>
>> Cc: Stefan Metzmacher <metze@samba.org>
>> Cc: <stable@vger.kernel.org> # 5.10+
> 
> The "# 5.10+" is now obsolete, and not needed. The Fixes tag is used to
> determine where this gets backported to.
> 
> Other than that. This patch looks good.

Great, thanks!

Mathieu

> 
> -- Steve
> 
>> ---
>>  kernel/tracepoint.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
>> index fc32821f8240..133b6454b287 100644
>> --- a/kernel/tracepoint.c
>> +++ b/kernel/tracepoint.c
>> @@ -338,7 +338,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
>>  	} else {
>>  		rcu_assign_pointer(tp->funcs, tp_funcs);
>>  		tracepoint_update_call(tp, tp_funcs,
>> -				       tp_funcs[0].func != old[0].func);
>> +				       tp_funcs[0].data != old[0].data);
>>  	}
>>  	release_probes(old);
> >  	return 0;

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

  reply	other threads:[~2021-08-05 17:57 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-05 13:27 [PATCH 0/3] tracepoint static call fixes Mathieu Desnoyers
2021-08-05 13:27 ` [PATCH 1/3] Fix: tracepoint: static call: compare data on transition from 2->1 callees Mathieu Desnoyers
2021-08-05 17:07   ` Steven Rostedt
2021-08-05 17:57     ` Mathieu Desnoyers [this message]
2021-08-05 13:27 ` [PATCH 2/3] Fix: tracepoint: static call function vs data state mismatch (v2) Mathieu Desnoyers
2021-08-05 18:56   ` Steven Rostedt
2021-08-05 19:15     ` Mathieu Desnoyers
2021-08-05 19:38       ` Steven Rostedt
2021-08-05 19:42         ` Mathieu Desnoyers
2021-08-05 13:27 ` [PATCH 3/3] Fix: tracepoint: rcu get state and cond sync for static call updates (v2) Mathieu Desnoyers
2021-08-05 19:12   ` Steven Rostedt
2021-08-05 19:29     ` [PATCH v3 1/1] Fix: tracepoint: rcu get state and cond sync for static call updates Mathieu Desnoyers

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