linux-kernel - [PATCH 5/7] um: irqs: allow invoking time-travel handler multiple times

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Date:   Tue, 23 Feb 2021 16:27:05 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     linux-um@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...nel.org>,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 5/7] um: irqs: allow invoking time-travel handler multiple times

From: Johannes Berg <johannes.berg@...el.com>

If we happen to get multiple messages while IRQS are already
suspended, we still need to handle them, since otherwise the
simulation blocks.

Remove the "prevent nesting" part, time_travel_add_irq_event()
will deal with being called multiple times just fine.

Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 arch/um/kernel/irq.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 76448b85292f..3718a5cdbc85 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -101,10 +101,12 @@ static bool irq_do_timetravel_handler(struct irq_entry *entry,
 	if (!reg->timetravel_handler)
 		return false;
 
-	/* prevent nesting - we'll get it again later when we SIGIO ourselves */
-	if (reg->pending_on_resume)
-		return true;
-
+	/*
+	 * Handle all messages - we might get multiple even while
+	 * interrupts are already suspended, due to suspend order
+	 * etc. Note that time_travel_add_irq_event() will not add
+	 * an event twice, if it's pending already "first wins".
+	 */
 	reg->timetravel_handler(reg->irq, entry->fd, reg->id, &reg->event);
 
 	if (!reg->event.pending)
-- 
2.26.2