Re: FAILED: patch "[PATCH] ftrace: Protect ftrace_graph_hash with ftrace_sync" failed to apply to 5.5-stable tree

[Sasha Levin <sashal@kernel.org>]

On Fri, Feb 07, 2020 at 08:28:42AM -0500, Steven Rostedt wrote:
>
>Hi Greg,
>
>On Fri, 07 Feb 2020 11:16:16 +0100
><gregkh@linuxfoundation.org> wrote:
>
>> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
>> index 8c52f5de9384..3c75d29bd861 100644
>> --- a/kernel/trace/trace.h
>> +++ b/kernel/trace/trace.h
>> @@ -979,6 +979,7 @@ static inline int ftrace_graph_addr(struct ftrace_graph_ent *trace)
>>  	 * Have to open code "rcu_dereference_sched()" because the
>>  	 * function graph tracer can be called when RCU is not
>>  	 * "watching".
>> +	 * Protected with schedule_on_each_cpu(ftrace_sync)
>>  	 */
>>  	hash = rcu_dereference_protected(ftrace_graph_hash, !preemptible());
>>
>> @@ -1031,6 +1032,7 @@ static inline int ftrace_graph_notrace_addr(unsigned long addr)
>>  	 * Have to open code "rcu_dereference_sched()" because the
>>  	 * function graph tracer can be called when RCU is not
>>  	 * "watching".
>> +	 * Protected with schedule_on_each_cpu(ftrace_sync)
>>  	 */
>>  	notrace_hash = rcu_dereference_protected(ftrace_graph_notrace_hash,
>>  						 !preemptible());
>
>Ah, I updated that patch to insert these comments, which makes it
>dependent on 16052dd5bdfa ("ftrace: Add comment to why
>rcu_dereference_sched() is open coded"). This is just adding comments
>and should have a very lower risk of breaking anything. If you add that
>patch first, then this patch should apply cleanly. Would it be OK to
>add that comment patch? It should fix most the conflicts.

I've ended up taking these additional commits, and queued everything for
5.5-4.14:

16052dd5bdfa ("ftrace: Add comment to why rcu_dereference_sched() is open coded")
24a9729f8314 ("tracing: Annotate ftrace_graph_hash pointer with __rcu")
fd0e6852c407 ("tracing: Annotate ftrace_graph_notrace_hash pointer with __rcu")

-- 
Thanks,
Sasha