The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 1b5fc84aba170bdfe3533396ca9662ceea1609b7 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin npiggin@gmail.com Date: Mon, 26 Nov 2018 12:01:05 +1000 Subject: [PATCH] powerpc/smp: Fix NMI IPI timeout
The NMI IPI timeout logic is broken, if __smp_send_nmi_ipi() times out on the first condition, delay_us will be zero which will send it into the second spin loop with no timeout so it will spin forever.
Fixes: 5b73151fff63 ("powerpc: NMI IPI make NMI IPIs fully sychronous") Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Nicholas Piggin npiggin@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index 3f15edf25a0d..137196a4248b 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -519,7 +519,7 @@ int __smp_send_nmi_ipi(int cpu, void (*fn)(struct pt_regs *), u64 delay_us, bool if (delay_us) { delay_us--; if (!delay_us) - break; + goto timeout; } }
@@ -530,10 +530,11 @@ int __smp_send_nmi_ipi(int cpu, void (*fn)(struct pt_regs *), u64 delay_us, bool if (delay_us) { delay_us--; if (!delay_us) - break; + goto timeout; } }
+timeout: if (!cpumask_empty(&nmi_ipi_pending_mask)) { /* Timeout waiting for CPUs to call smp_handle_nmi_ipi */ ret = 0;