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Fri, 23 Jan 2026 23:49:52 -0800 (PST) X-Received: by 2002:a05:6000:601:b0:430:fdc8:8bbd with SMTP id ffacd0b85a97d-435b16039damr9146785f8f.41.1769240992303; Fri, 23 Jan 2026 23:49:52 -0800 (PST) MIME-Version: 1.0 References: <20250611224604.313496-2-seanjc@google.com> <20250611224604.313496-40-seanjc@google.com> <42513cb3-3c2e-4aa8-b748-23b6656a5096@redhat.com> <874iovu742.ffs@tglx> <87pl7jsrdg.ffs@tglx> <5bea843b-dec8-4f15-bb7c-1d0550542034@redhat.com> <87sebxtrgp.ffs@tglx> In-Reply-To: <87sebxtrgp.ffs@tglx> From: Paolo Bonzini Date: Sat, 24 Jan 2026 08:49:40 +0100 X-Gm-Features: AZwV_Qj6aLwVSas8vwNUo-Ndu2FBevRcUQp0THPxC18GLGDTRk3JARciXPkQtdQ Message-ID: Subject: Re: possible deadlock due to irq_set_thread_affinity() calling into the scheduler (was Re: [PATCH v3 38/62] KVM: SVM: Take and hold ir_list_lock across IRTE updates in IOMMU) To: Thomas Gleixner Cc: Ankit Soni , Sean Christopherson , Marc Zyngier , Oliver Upton , Joerg Roedel , David Woodhouse , Lu Baolu , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Sairaj Kodilkar , Vasant Hegde , Maxim Levitsky , Joao Martins , Francesco Lavra , David Matlack , Naveen Rao , Crystal Wood X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 7ru7QbTJjFw8kabGXasXuGhubbYcuJoq8j_eB1LYGxQ_1769240993 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260123_234958_767790_17FF5E13 X-CRM114-Status: GOOD ( 16.35 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jan 22, 2026 at 7:47=E2=80=AFPM Thomas Gleixner w= rote: > > On Wed, Jan 21 2026 at 19:13, Paolo Bonzini wrote: > > On 1/8/26 22:53, Thomas Gleixner wrote: > >> Are you still claiming that this is a kernel/irq bug? > > > > Not really, I did say I'd like to treat it as a kernel/irq bug... > > but certainly didn't have hopes high enough to "claim" that. > > I do think that it's ugly to have locks that are internal, > > non-leaf and held around callbacks; but people smarter than > > me have thought about it and you can't call it a bug anyway. > > Deep core code has a tendency to be ugly. But if it makes your life > easier, then these wakeups can be delayed via an irq_work to be outside > of the lock. That needs some life-time issues to be addressed, but > should be doable. Thanks for the suggestion---hopefully it's not needed at all and we can delay taking the lock in KVM. Paolo