From 6bbc2b2245c5b006824eb42ef33d5b296158a693 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Thu, 11 Jul 2019 10:38:56 -0400
Subject: [PATCH] cosmetic changes

---
 kernel/trap.c        | 20 ++++++++++++++------
 kernel/virtio_disk.c | 16 ++++++++--------
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/kernel/trap.c b/kernel/trap.c
index eb7f6cf..ea5799f 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -158,6 +158,15 @@ kerneltrap()
   w_sstatus(sstatus);
 }
 
+void
+clockintr()
+{
+  acquire(&tickslock);
+  ticks++;
+  wakeup(&ticks);
+  release(&tickslock);
+}
+
 // check if it's an external interrupt or software interrupt,
 // and handle it.
 // returns 2 if timer interrupt,
@@ -182,16 +191,15 @@ devintr()
     plic_complete(irq);
     return 1;
   } else if(scause == 0x8000000000000001){
-    // software interrupt from a machine-mode timer interrupt.
+    // software interrupt from a machine-mode timer interrupt,
+    // forwarded by machinevec in kernelvec.S.
 
     if(cpuid() == 0){
-      acquire(&tickslock);
-      ticks++;
-      wakeup(&ticks);
-      release(&tickslock);
+      clockintr();
     }
     
-    // acknowledge.
+    // acknowledge the software interrupt by clearing
+    // the SSIP bit in sip.
     w_sip(r_sip() & ~2);
 
     return 2;
diff --git a/kernel/virtio_disk.c b/kernel/virtio_disk.c
index 8637b56..1a29ce7 100644
--- a/kernel/virtio_disk.c
+++ b/kernel/virtio_disk.c
@@ -20,7 +20,7 @@
 // the address of virtio mmio register r.
 #define R(r) ((volatile uint32 *)(VIRTIO0 + (r)))
 
-struct spinlock virtio_disk_lock;
+struct spinlock vdisk_lock;
 
 // memory for virtio descriptors &c for queue 0.
 // this is a global instead of allocated because it has
@@ -49,7 +49,7 @@ virtio_disk_init(void)
 {
   uint32 status = 0;
 
-  initlock(&virtio_disk_lock, "virtio_disk");
+  initlock(&vdisk_lock, "virtio_disk");
 
   if(*R(VIRTIO_MMIO_MAGIC_VALUE) != 0x74726976 ||
      *R(VIRTIO_MMIO_VERSION) != 1 ||
@@ -168,7 +168,7 @@ virtio_disk_rw(struct buf *b)
 {
   uint64 sector = b->blockno * (BSIZE / 512);
 
-  acquire(&virtio_disk_lock);
+  acquire(&vdisk_lock);
 
   // the spec says that legacy block operations use three
   // descriptors: one for type/reserved/sector, one for
@@ -180,7 +180,7 @@ virtio_disk_rw(struct buf *b)
     if(alloc3_desc(idx) == 0) {
       break;
     }
-    sleep(&free[0], &virtio_disk_lock);
+    sleep(&free[0], &vdisk_lock);
   }
   
   // format the three descriptors.
@@ -234,16 +234,16 @@ virtio_disk_rw(struct buf *b)
 
   // Wait for virtio_disk_intr() to say request has finished.
   while((b->flags & (B_VALID|B_DIRTY)) != B_VALID){
-    sleep(b, &virtio_disk_lock);
+    sleep(b, &vdisk_lock);
   }
 
-  release(&virtio_disk_lock);
+  release(&vdisk_lock);
 }
 
 void
 virtio_disk_intr()
 {
-  acquire(&virtio_disk_lock);
+  acquire(&vdisk_lock);
 
   while((used_idx % NUM) != (used->id % NUM)){
     int id = used->elems[used_idx].id;
@@ -262,5 +262,5 @@ virtio_disk_intr()
     used_idx = (used_idx + 1) % NUM;
   }
 
-  release(&virtio_disk_lock);
+  release(&vdisk_lock);
 }