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[193.116.82.75]) by smtp.gmail.com with ESMTPSA id k16sm12748001pgm.26.2022.01.24.06.39.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Jan 2022 06:39:36 -0800 (PST) From: Nicholas Piggin To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH 1/3] powerpc/64s/interrupt: Fix decrementer storm Date: Tue, 25 Jan 2022 00:39:28 +1000 Message-Id: <20220124143930.3923442-1-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , Nicholas Piggin Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" The decrementer exception can fail to be cleared when the interrupt returns in the case where the decrementer wraps with the next timer still beyond decrementer_max. This results in a decrementer interrupt storm. This is triggerable with small decrementer system with hard and soft watchdogs disabled. Fix this by always programming the decrementer if there was no timer. Fixes: 0faf20a1ad16 ("powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is in use") Reported-by: Alexey Kardashevskiy Signed-off-by: Nicholas Piggin --- arch/powerpc/kernel/time.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 62361cc7281c..cd0b8b71ecdd 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -649,8 +649,9 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(timer_interrupt) __this_cpu_inc(irq_stat.timer_irqs_event); } else { now = *next_tb - now; - if (now <= decrementer_max) - set_dec_or_work(now); + if (now > decrementer_max) + now = decrementer_max; + set_dec_or_work(now); __this_cpu_inc(irq_stat.timer_irqs_others); }