From: Ihor Solodrai <ihor.solodrai@linux.dev>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: Steven Rostedt <rostedt@kernel.org>,
Florent Revest <revest@google.com>,
Mark Rutland <mark.rutland@arm.com>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-trace-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Menglong Dong <menglong8.dong@gmail.com>,
Song Liu <song@kernel.org>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>
Subject: Re: [PATCHv6 bpf-next 9/9] bpf,x86: Use single ftrace_ops for direct calls
Date: Fri, 27 Feb 2026 14:00:58 -0800 [thread overview]
Message-ID: <dc7fb8ff-def1-4d9f-8025-c7da49a1a902@linux.dev> (raw)
In-Reply-To: <aaILlSuEgaYDq41r@krava>
On 2/27/26 1:24 PM, Jiri Olsa wrote:
> On Fri, Feb 27, 2026 at 09:37:52PM +0100, Jiri Olsa wrote:
>> [...]
>>
>>>
>>> With CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS ftrace_replace_code()
>>> operates on all call sites in the shared ops. Then if a concurrent
>>> ftrace user (like kprobe) modifies a call site in between
>>> ftrace_replace_code's verify pass and its patch pass, then ftrace_bug
>>> fires and sets ftrace_disabled to 1.
>>
>> hum, I'd think that's all under ftrace_lock/direct_mutex,
>> but we might be missing some paths
>>
>
> could you please try with change below? I can no longer trigger the bug with it
Can confirm that the bug doesn't trigger with this change.
At least by the reproducer test.
Tested-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Thanks!
>
> thanks,
> jirka
>
>
> ---
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 827fb9a0bf0d..e333749a5896 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -6404,7 +6404,9 @@ int update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace_hash *hash)
> new_filter_hash = old_filter_hash;
> }
> } else {
> + mutex_lock(&ftrace_lock);
> err = ftrace_update_ops(ops, new_filter_hash, EMPTY_HASH);
> + mutex_unlock(&ftrace_lock);
> /*
> * new_filter_hash is dup-ed, so we need to release it anyway,
> * old_filter_hash either stays on error or is already released
> @@ -6530,7 +6532,9 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)
> ops->func_hash->filter_hash = NULL;
> }
> } else {
> + mutex_lock(&ftrace_lock);
> err = ftrace_update_ops(ops, new_filter_hash, EMPTY_HASH);
> + mutex_unlock(&ftrace_lock);
> /*
> * new_filter_hash is dup-ed, so we need to release it anyway,
> * old_filter_hash either stays on error or is already released
next prev parent reply other threads:[~2026-02-27 22:01 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-30 14:50 [PATCHv6 bpf-next 0/9] ftrace,bpf: Use single direct ops for bpf trampolines Jiri Olsa
2025-12-30 14:50 ` [PATCHv6 bpf-next 1/9] ftrace,bpf: Remove FTRACE_OPS_FL_JMP ftrace_ops flag Jiri Olsa
2026-01-10 0:36 ` Andrii Nakryiko
2025-12-30 14:50 ` [PATCHv6 bpf-next 2/9] ftrace: Make alloc_and_copy_ftrace_hash direct friendly Jiri Olsa
2025-12-30 14:50 ` [PATCHv6 bpf-next 3/9] ftrace: Export some of hash related functions Jiri Olsa
2025-12-30 14:50 ` [PATCHv6 bpf-next 4/9] ftrace: Add update_ftrace_direct_add function Jiri Olsa
2025-12-30 14:50 ` [PATCHv6 bpf-next 5/9] ftrace: Add update_ftrace_direct_del function Jiri Olsa
2025-12-30 14:50 ` [PATCHv6 bpf-next 6/9] ftrace: Add update_ftrace_direct_mod function Jiri Olsa
2025-12-30 14:50 ` [PATCHv6 bpf-next 7/9] bpf: Add trampoline ip hash table Jiri Olsa
2026-01-10 0:36 ` Andrii Nakryiko
2026-01-12 21:27 ` Jiri Olsa
2026-01-13 11:02 ` Alan Maguire
2026-01-13 11:58 ` Jiri Olsa
2025-12-30 14:50 ` [PATCHv6 bpf-next 8/9] ftrace: Factor ftrace_ops ops_func interface Jiri Olsa
2025-12-30 14:50 ` [PATCHv6 bpf-next 9/9] bpf,x86: Use single ftrace_ops for direct calls Jiri Olsa
2026-01-10 0:36 ` Andrii Nakryiko
2026-02-27 17:40 ` Ihor Solodrai
2026-02-27 20:37 ` Jiri Olsa
2026-02-27 21:24 ` Jiri Olsa
2026-02-27 22:00 ` Ihor Solodrai [this message]
2026-02-28 20:39 ` Steven Rostedt
2026-03-02 8:08 ` Jiri Olsa
2026-03-02 15:10 ` Steven Rostedt
2026-01-15 18:54 ` [PATCHv6 bpf-next 0/9] ftrace,bpf: Use single direct ops for bpf trampolines Andrii Nakryiko
2026-01-26 9:48 ` Jiri Olsa
2026-01-28 14:48 ` Steven Rostedt
2026-01-28 20:00 ` patchwork-bot+netdevbpf
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