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[104.155.91.135]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49e7d6a9d1dsm52818775e9.10.2026.09.15.00.23.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Sep 2026 00:23:58 -0700 (PDT) Date: Tue, 15 Sep 2026 08:23:55 +0100 From: Vincent Donnefort To: David CARLIER Cc: rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, kernel-team@android.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] ring-buffer: Clean up resize_disabled checks Message-ID: References: <20260914175907.1027349-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Sep 14, 2026 at 08:09:24PM +0100, David CARLIER wrote: > Hi Vincent. > > > + if (rb_resize_disabled(buffer, cpu_id)) { > > + err = -EBUSY; > > + goto out_err_unlock; > > + } > > For a single CPU, this now happens before the nr_pages == cpu_buffer->nr_pages > early exit, so writing the same size to per_cpu/cpuN/buffer_size_kb on a > mapped or persistent instance CPU fails with EBUSY instead of succeeding. > Intended ? Actually no, I didn't see that it is also "fixing" this discrepancy between the per_cpu buffer_size_kb and the global one. It seems to me better to align the behaviour for both interface, but then it is touching something that is user interface... Steven, WDYS? > > > Additionally, remove the unnecessary cpumask_test_cpu in > > ring_buffer_subbuf_order_set(). > > The install loop still has one. > > Otherwise removing the second check is fine, the hotplug window is > covered by the cpus_read_lock() patch I sent separately. > > Cheers. -- Vincent