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Mon, 21 Jul 2025 08:05:39 -0700 (PDT) From: Liangyan X-Google-Original-From: Liangyan Message-ID: Date: Mon, 21 Jul 2025 23:05:34 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [External] [patch 0/4] genirq: Prevent migration live lock in handle_edge_irq() To: Thomas Gleixner , LKML Cc: Liangyan , Yicong Shen , Jiri Slaby References: <20250718184935.232983339@linutronix.de> Content-Language: en-US In-Reply-To: <20250718184935.232983339@linutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2025/7/19 02:54, Thomas Gleixner wrote: > Yicon reported and Liangyan debugged a live lock in handle_edge_irq() > related to interrupt migration. > > If the interrupt affinity is moved to a new target CPU and the interrupt is > currently handled on the previous target CPU for edge type interrupts the > handler might get stuck on the previous target: > > CPU 0 (previous target) CPU 1 (new target) > > handle_edge_irq() > repeat: > handle_event() handle_edge_irq() > if (INPROGESS) { > set(PENDING); > mask(); > return; > } > if (PENDING) { > clear(PENDING); > unmask(); > goto repeat; > } > > The migration in software never completes and CPU0 continues to handle the > pending events forever. This happens when the device raises interrupts with > a high rate and always before handle_event() completes and before the CPU0 > handler can clear INPROGRESS so that CPU1 sets the PENDING flag over and > over. This has been observed in virtual machines. > > The following series is addressing this by making the new target CPU wait > for the handler to complete on CPU1 and thereby completing the software > migration. > > A draft combo patch of this has been tested by Liangyan: > > https://lore.kernel.org/all/87o6u0rpaa.ffs@tglx > > The series splits up the draft patch and has proper changelogs. > > Thanks, > > tglx > --- > chip.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++-------- > internals.h | 6 ++--- > pm.c | 16 +++++--------- > spurious.c | 37 -------------------------------- > 4 files changed, 69 insertions(+), 58 deletions(-) > > Tested-by: Liangyan Regards, Liangyan