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Mon, 25 May 2026 00:40:05 -0700 (PDT) Received: from localhost.localdomain ([2408:8607:1b00:8:b4f2:93ab:3f87:70e7]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84164aed7c9sm10298358b3a.13.2026.05.25.00.39.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 May 2026 00:40:04 -0700 (PDT) From: Li Pengfei X-Google-Original-From: Li Pengfei To: mhiramat@kernel.org Cc: linux-trace-kernel@vger.kernel.org, rostedt@goodmis.org, linux-kernel@vger.kernel.org, cmllamas@google.com, zhangbo56@xiaomi.com, lipengfei28@xiaomi.com, lkp@intel.com Subject: Re: [RFC PATCH v2 0/3] trace: stack trace deduplication for ftrace ring buffer Date: Mon, 25 May 2026 15:39:07 +0800 Message-Id: <20260525073907.2355900-1-lipengfei28@xiaomi.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260525155841.b15adcd50d25485aab287043@kernel.org> References: <20260525155841.b15adcd50d25485aab287043@kernel.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Masami, I went through the Sashiko comments on v2 [1]. Per-finding response below; v3 will incorporate the fixes. [1] https://sashiko.dev/#/patchset/20260522104017.1668638-1-lipengfei28%40xiaomi.com Patch 1/3: - memset() torn reads against lockless readers: agreed, the reset path is not well serialized against tracefs readers. Will tighten slow-path synchronization in v3. - seq_next() not advancing *pos on EOF: agreed, will fix in v3. - atomic_read(&resetting) without acquire: agreed, will switch to atomic_read_acquire() in v3. - Plain reads of entry->key: agreed, will use READ_ONCE() in v3. - atomic64_inc() in NMI-safe hot path on 32-bit GENERIC_ATOMIC64: agreed, will move the counters off the hot path (local_t / per-CPU) in v3. Patch 2/3: - TRACE_STACK_ID not in trace_valid_entry(): agreed, will add in v3. - "NULL from kzalloc" comment: wording bug, will correct in v3. - Reset memset synchronization: same fix as patch 1, finding 1. Patch 3/3: - Selftest missing 'function:tracer' in '# requires:': agreed, will add in v3. - Selftest wiping the ring buffer via 'echo nop > current_tracer' before reading trace: agreed, will reorder in v3. I'll send v3 once the changes are tested. Pengfei