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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.19 065/113] powerpc/smp: Fix NMI IPI timeout
Date:   Wed, 15 May 2019 12:55:56 +0200
Message-Id: <20190515090658.482728040@linuxfoundation.org>
In-Reply-To: <20190515090652.640988966@linuxfoundation.org>
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[ Upstream commit 1b5fc84aba170bdfe3533396ca9662ceea1609b7 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/powerpc/kernel/smp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 61c1fadbc6444..22abba5f4cf0e 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -499,7 +499,7 @@ 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;
 		}
 	}
 
@@ -510,10 +510,11 @@ 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;
-- 
2.20.1