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([2001:a61:1340:dc01:654b:3cf0:59cd:498]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cfd3f8192sm264862305e9.3.2026.09.07.04.38.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Sep 2026 04:38:54 -0700 (PDT) Message-ID: <6e0dbfed-cadd-4274-8165-886725413d0f@suse.com> Date: Mon, 7 Sep 2026 13:38:53 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v2] usbnet: fix smp_processor_id() use in preemptible context To: =?UTF-8?Q?=C3=96mer_Mete_Kaya?= , netdev@vger.kernel.org Cc: oneukum@suse.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+04cd90bb99c6ef81a65d@syzkaller.appspotmail.com References: <20260903165456.498079-1-omermetekaya0@gmail.com> <20260905224553.595766-1-omermetekaya0@gmail.com> Content-Language: en-US From: Oliver Neukum In-Reply-To: <20260905224553.595766-1-omermetekaya0@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 06.09.26 00:45, Ömer Mete Kaya wrote: > usbnet_skb_return() and tx_complete() call this_cpu_ptr() before > disabling IRQs, which triggers a BUG when running with PREEMPT_FULL: > > BUG: using smp_processor_id() in preemptible code in tx_complete > > Fix by saving IRQs first with local_irq_save(), then calling > this_cpu_ptr() and using the non-irqsave variants of u64_stats > update helpers, since IRQs are already disabled at that point. Hi, thank you for the patch. However, if the problem is preemption, when not simply preempt_disable()/peempt_enable()? Why is it necessary to switch off interrupts? Regards Oliver