[PATCH 5.0 166/238] powerpc/smp: Fix NMI IPI timeout

[Greg Kroah-Hartman]

5.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Piggin <npiggin@xxxxxxxxx>

commit 1b5fc84aba170bdfe3533396ca9662ceea1609b7 upstream.

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@xxxxxxxxxxxxxxx # v4.19+
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/powerpc/kernel/smp.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -519,7 +519,7 @@ int __smp_send_nmi_ipi(int cpu, void (*f
 		if (delay_us) {
 			delay_us--;
 			if (!delay_us)
-				break;
+				goto timeout;
 		}
 	}
 
@@ -530,10 +530,11 @@ int __smp_send_nmi_ipi(int cpu, void (*f
 		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;