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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Sebastian Siewior <bigeasy@linutronix.de>,
	Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: [patch 1/2] x86/ioapic: Prevent inconsistent state when moving an interrupt
Date: Thu, 17 Oct 2019 12:19:01 +0200
Message-ID: <20191017101938.321393687@linutronix.de> (raw)
In-Reply-To: <20191017101900.925994783@linutronix.de>

There is an issue with threaded interrupts which are marked ONESHOT
and using the fasteoi handler.

  if (IS_ONESHOT())
    mask_irq();
  ....
  cond_unmask_eoi_irq()
    chip->irq_eoi();
      if (setaffinity_pending) {
         mask_ioapic();
         ...
	 move_affinity();
	 unmask_ioapic();
      }

So if setaffinity is pending the interrupt will be moved and then
unconditionally unmasked at the ioapic level, which is wrong in two
aspects:

 1) It should be kept masked up to the point where the threaded handler
    finished.

 2) The physical chip state and the software masked state are inconsistent

Guard both the mask and the unmask with a check for the software masked
state. If the line is marked masked then the ioapic line is also masked, so
both mask_ioapic() and unmask_ioapic() can be skipped safely.

Fixes: 3aa551c9b4c4 ("genirq: add threaded interrupt handler support")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/apic/io_apic.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1729,7 +1729,8 @@ static inline bool ioapic_irqd_mask(stru
 {
 	/* If we are moving the irq we need to mask it */
 	if (unlikely(irqd_is_setaffinity_pending(data))) {
-		mask_ioapic_irq(data);
+		if (!irqd_irq_masked(data))
+			mask_ioapic_irq(data);
 		return true;
 	}
 	return false;
@@ -1766,7 +1767,9 @@ static inline void ioapic_irqd_unmask(st
 		 */
 		if (!io_apic_level_ack_pending(data->chip_data))
 			irq_move_masked_irq(data);
-		unmask_ioapic_irq(data);
+		/* If the irq is masked in the core, leave it */
+		if (!irqd_irq_masked(data))
+			unmask_ioapic_irq(data);
 	}
 }
 #else



  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-17 10:19 [patch 0/2] x86/ioapic: Prevent inconsistent state Thomas Gleixner
2019-10-17 10:19 ` Thomas Gleixner [this message]
2019-10-24 10:13   ` [tip: x86/apic] x86/ioapic: Prevent inconsistent state when moving an interrupt tip-bot2 for Thomas Gleixner
2019-10-17 10:19 ` [patch 2/2] x86/ioapic: Rename misnamed functions Thomas Gleixner
2019-10-24 10:13   ` [tip: x86/apic] " tip-bot2 for Thomas Gleixner

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