From 097f9cf735ffa1212b828682ad92f0f6c5f1c552 Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Mon, 11 Nov 2019 23:50:03 +0100
Subject: irq: Add disabling counter

* linux/dev/arch/i386/kernel/irq.c (ndisabled_irq): New array.
(__disable_irq, __enable_irq): New functions, count with ndisabled_irq
before really calling mask_irq/unmask_irq.
(linux_pic_mask): New variable.
(disable_irq, enable_irq): Manage linux_pic_mask and call
__disable_irq/__enable_irq instead of calling mask_irq/unmask_irq.
* linux/src/include/asm-i386/irq.h (__disable_irq, __enable_irq): New
prototypes.
---
 linux/dev/arch/i386/kernel/irq.c | 55 +++++++++++++++++++++++++++++++++++++---
 linux/src/include/asm-i386/irq.h |  2 ++
 2 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/linux/dev/arch/i386/kernel/irq.c b/linux/dev/arch/i386/kernel/irq.c
index 75f8f812..18448638 100644
--- a/linux/dev/arch/i386/kernel/irq.c
+++ b/linux/dev/arch/i386/kernel/irq.c
@@ -158,8 +158,13 @@ unmask_irq (unsigned int irq_nr)
     }
 }
 
+/* Count how many subsystems requested to disable each IRQ */
+static unsigned ndisabled_irq[NR_IRQS];
+
+/* These disable/enable IRQs for real after counting how many subsystems
+ * requested that */
 void
-disable_irq (unsigned int irq_nr)
+__disable_irq (unsigned int irq_nr)
 {
   unsigned long flags;
 
@@ -167,12 +172,15 @@ disable_irq (unsigned int irq_nr)
 
   save_flags (flags);
   cli ();
-  mask_irq (irq_nr);
+  ndisabled_irq[irq_nr]++;
+  assert (ndisabled_irq[irq_nr] > 0);
+  if (ndisabled_irq[irq_nr] == 1)
+    mask_irq (irq_nr);
   restore_flags (flags);
 }
 
 void
-enable_irq (unsigned int irq_nr)
+__enable_irq (unsigned int irq_nr)
 {
   unsigned long flags;
 
@@ -180,7 +188,46 @@ enable_irq (unsigned int irq_nr)
 
   save_flags (flags);
   cli ();
-  unmask_irq (irq_nr);
+  assert (ndisabled_irq[irq_nr] > 0);
+  ndisabled_irq[irq_nr]--;
+  if (ndisabled_irq[irq_nr] == 0)
+    unmask_irq (irq_nr);
+  restore_flags (flags);
+}
+
+/* IRQ mask according to Linux drivers */
+static unsigned linux_pic_mask;
+
+/* These only record that Linux requested to mask IRQs */
+void
+disable_irq (unsigned int irq_nr)
+{
+  unsigned long flags;
+  unsigned mask = 1U << irq_nr;
+
+  save_flags (flags);
+  cli ();
+  if (!(linux_pic_mask & mask))
+  {
+    linux_pic_mask |= mask;
+    __disable_irq(irq_nr);
+  }
+  restore_flags (flags);
+}
+
+void
+enable_irq (unsigned int irq_nr)
+{
+  unsigned long flags;
+  unsigned mask = 1U << irq_nr;
+
+  save_flags (flags);
+  cli ();
+  if (linux_pic_mask & mask)
+  {
+    linux_pic_mask &= ~mask;
+    __enable_irq(irq_nr);
+  }
   restore_flags (flags);
 }
 
diff --git a/linux/src/include/asm-i386/irq.h b/linux/src/include/asm-i386/irq.h
index c75744a5..d7d1e3c5 100644
--- a/linux/src/include/asm-i386/irq.h
+++ b/linux/src/include/asm-i386/irq.h
@@ -16,6 +16,8 @@
 
 #define TIMER_IRQ 0
 
+extern void __disable_irq(unsigned int);
+extern void __enable_irq(unsigned int);
 extern void disable_irq(unsigned int);
 extern void enable_irq(unsigned int);
 
-- 
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