[PATCH] xtensa: add fairness to IRQ handling

[Max Filippov]

Track which IRQs have been served at each level to make sure that no IRQ
is served more than once while other IRQs at the same level are pending.

Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
---
 arch/xtensa/kernel/traps.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index efc3a29cde80..874b6efc6fb3 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -268,6 +268,7 @@ void do_interrupt(struct pt_regs *regs)
 		XCHAL_INTLEVEL7_MASK,
 	};
 	struct pt_regs *old_regs;
+	unsigned unhandled = ~0u;
 
 	trace_hardirqs_off();
 
@@ -283,6 +284,10 @@ void do_interrupt(struct pt_regs *regs)
 		for (level = LOCKLEVEL; level > 0; --level) {
 			if (int_at_level & int_level_mask[level]) {
 				int_at_level &= int_level_mask[level];
+				if (int_at_level & unhandled)
+					int_at_level &= unhandled;
+				else
+					unhandled |= int_level_mask[level];
 				break;
 			}
 		}
@@ -290,6 +295,8 @@ void do_interrupt(struct pt_regs *regs)
 		if (level == 0)
 			break;
 
+		/* clear lowest pending irq in the unhandled mask */
+		unhandled ^= (int_at_level & -int_at_level);
 		do_IRQ(__ffs(int_at_level), regs);
 	}
 
-- 
2.20.1