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([2a00:23c6:9e09:2900:3d38:90c1:858b:902e]) by smtp.gmail.com with ESMTPSA id d9sm6916462wmd.10.2020.05.12.04.39.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 May 2020 04:39:17 -0700 (PDT) Subject: Re: x86/smp: adding new trace points From: Wojciech Kudla To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org References: <4d54953b-f968-63f5-569f-9e09bc0f361c@gmail.com> Message-ID: Date: Tue, 12 May 2020 12:39:17 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <4d54953b-f968-63f5-569f-9e09bc0f361c@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, I was trying to trace some IPIs (remote tlb shootdowns in this case) and noticed that: 1) irq_vectors:x86_platform_ipi_entry and irq_vectors:x86_platform_ipi_exit are not hit at all for my case. The backtrace on the receiving CPU: 0xffffffff81079535 flush_tlb_func_common.constprop.10+0x105/0x220 [kernel] 0xffffffff81079681 flush_tlb_func_remote+0x31/0x40 [kernel] 0xffffffff8111f76c flush_smp_call_function_queue+0x4c/0xf0 [kernel] 0xffffffff81120253 generic_smp_call_function_single_interrupt+0x13/0x30 [kernel] 0xffffffff81a030c6 smp_call_function_single_interrupt+0x36/0xd0 [kernel] 0xffffffff81a02679 call_function_single_interrupt+0xa9/0xb0 [kernel] I would expect that we would hit those trace point somewhere around call_function_single_interrupt() 2) there is no equivalent of ipi:ipi_raise for x86. For the following call stack: 0xffffffff81055d10 native_send_call_func_single_ipi+0x0/0x20 [kernel] 0xffffffff8111f86f generic_exec_single+0x5f/0xc0 [kernel] 0xffffffff8111f9a2 smp_call_function_single+0xd2/0x100 [kernel] 0xffffffff8111fe3c smp_call_function_many+0x1cc/0x250 [kernel] 0xffffffff8107982c native_flush_tlb_others+0x3c/0xf0 [kernel] (...) I would expect to have a irq_vectors:x86_platform_ipi_raise (or similar) tracepoint. Are there any reasons my expectations are wrong? I'd love to submit a patch that addresses these issue but I'd rather get some more context (history maybe) before that. Thanks, Wojtek