[PATCH AUTOSEL 4.19 64/81] powerpc/smp: Fix NMI IPI timeout

Sasha Levin
2019-05-07T05:56:42Z

From: Nicholas Piggin <npiggin@gmail.com>

[ 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 61c1fadbc644..22abba5f4cf0 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