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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id q10sm992748eds.67.2021.03.11.02.19.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Mar 2021 02:19:05 -0800 (PST) From: Vitaly Kuznetsov To: Thomas Gleixner , x86@kernel.org Cc: Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC 0/2] x86/apic: Avoid cm->allocated going negative in irq_matrix In-Reply-To: <20210219113101.967508-1-vkuznets@redhat.com> References: <20210219113101.967508-1-vkuznets@redhat.com> Date: Thu, 11 Mar 2021 11:19:04 +0100 Message-ID: <87ft129enb.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vitaly Kuznetsov writes: > I discovered that CPU0 offlining/onlining works only once: > > # echo 0 > /sys/devices/system/cpu/cpu0/online > # echo 1 > /sys/devices/system/cpu/cpu0/online > # echo 0 > /sys/devices/system/cpu/cpu0/online > -bash: echo: write error: No space left on device > > with the following in dmesg: > > [ ... ] CPU 0 has 4294967295 vectors, 589 available. Cannot disable CPU > > And the problem seems to be that irq_matrix_assign()/irq_matrix_free() calls > for PIC_CASCADE_IR are unbalanced, making cm->allocated go negative. > > RFC as I didn't quite get why we're making an exception for PIC_CASCADE_IR in > the first place. Surely it is special, but for the sake of consistency we'd > better not treat it as such. Or maybe I just misunderstood everything. > If the RFC part is the only thing which scares everyone off I'm ready to drop it and pretend that I'm confident with the change) > Vitaly Kuznetsov (2): > x86/apic: Do not make an exception for PIC_CASCADE_IR when marking > legacy irqs in irq_matrix > genirq/matrix: WARN_ON_ONCE() when cm->allocated/m->total_allocated go > negative > > arch/x86/kernel/apic/vector.c | 3 +-- > kernel/irq/matrix.c | 11 +++++++++-- > 2 files changed, 10 insertions(+), 4 deletions(-) -- Vitaly