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Sat, 30 May 2026 13:26:03 -0700 (PDT) Received: from localhost ([2600:1702:7a90:6f9f:8bc4:8aec:108d:7a04]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-66069abb92csm1148658d50.18.2026.05.30.13.26.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 30 May 2026 13:26:02 -0700 (PDT) From: Matt Turner To: linux-alpha@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Richard Henderson , Magnus Lindholm , Ivan Kokshaysky , Matt Turner Subject: [PATCH 3/3] alpha: Break down rescued IPI counter by type in /proc/interrupts Date: Sat, 30 May 2026 16:25:44 -0400 Message-ID: <20260530202544.59231-4-mattst88@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260530202544.59231-1-mattst88@gmail.com> References: <20260530202544.59231-1-mattst88@gmail.com> Precedence: bulk X-Mailing-List: linux-alpha@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add per-type rescued IPI counters to cpuinfo_alpha: rescued_reschedule_count (RIP:) rescued_call_func_count (RIF:) rescued_cpu_stop_count (RIS:) alpha_poll_ipi_inirq() peeks at ipi_data[cpu].bits before handle_ipi() clears them via xchg(), then increments the appropriate per-CPU counter. Expose all three as separate rows in /proc/interrupts alongside the existing "IPI:" row. This lets us distinguish the deadlock-causing subset (RIF: IPI_CALL_FUNC, of which wait=1 callers are the ones that deadlock) from the harmless majority (RIP: reschedule). A non-zero RIF count confirms the EV7/IO7 edge-triggered IPI loss hypothesis. Note: handle_ipi() also increments ipi_count unconditionally, so the "IPI:" row in /proc/interrupts includes both normal and rescued deliveries. The RIP:/RIF:/RIS: counters sample bits before the xchg(); bits that arrive after the READ_ONCE are drained by handle_ipi() but not reflected in these counters — they are approximate but sufficient for diagnosis. Assisted-by: Claude:claude-sonnet-4-6 Signed-off-by: Matt Turner --- arch/alpha/include/asm/smp.h | 3 +++ arch/alpha/kernel/irq.c | 12 ++++++++++++ 2 files changed, 15 insertions(+) diff --git ./arch/alpha/include/asm/smp.h ./arch/alpha/include/asm/smp.h index 8bd529376cf6..98f522ee367f 100644 --- ./arch/alpha/include/asm/smp.h +++ ./arch/alpha/include/asm/smp.h @@ -31,6 +31,9 @@ struct cpuinfo_alpha { int need_new_asn; int asn_lock; unsigned long ipi_count; + unsigned long rescued_reschedule_count; + unsigned long rescued_call_func_count; + unsigned long rescued_cpu_stop_count; unsigned long prof_multiplier; unsigned long prof_counter; unsigned char mcheck_expected; diff --git ./arch/alpha/kernel/irq.c ./arch/alpha/kernel/irq.c index c67047c5d830..34709e1c42c5 100644 --- ./arch/alpha/kernel/irq.c +++ ./arch/alpha/kernel/irq.c @@ -76,6 +76,18 @@ int arch_show_interrupts(struct seq_file *p, int prec) for_each_online_cpu(j) seq_printf(p, "%10lu ", cpu_data[j].ipi_count); seq_putc(p, '\n'); + seq_puts(p, "RIP: "); + for_each_online_cpu(j) + seq_printf(p, "%10lu ", cpu_data[j].rescued_reschedule_count); + seq_puts(p, " Rescued IPIs: reschedule\n"); + seq_puts(p, "RIF: "); + for_each_online_cpu(j) + seq_printf(p, "%10lu ", cpu_data[j].rescued_call_func_count); + seq_puts(p, " Rescued IPIs: call function\n"); + seq_puts(p, "RIS: "); + for_each_online_cpu(j) + seq_printf(p, "%10lu ", cpu_data[j].rescued_cpu_stop_count); + seq_puts(p, " Rescued IPIs: cpu stop\n"); #endif seq_puts(p, "PMI: "); for_each_online_cpu(j) -- 2.53.0