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authorFrans Kaashoek <[email protected]>2017-02-01 20:36:41 -0500
committerFrans Kaashoek <[email protected]>2017-02-01 20:36:41 -0500
commitc9fa90f7e514f27fa1ac071cd9795f3830ab6a1b (patch)
tree2bfaf92fbd2a649247af758c8e8967f7df3c45ac
parent2e2d14c235b570a6beb222fc1bfa53de85a98de3 (diff)
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A tiny bit of clean up (e.g., move code searching cpu array from lapic.c into
mycpu() in proc.c.
-rw-r--r--console.c2
-rw-r--r--defs.h2
-rw-r--r--lapic.c15
-rw-r--r--proc.c15
4 files changed, 17 insertions, 17 deletions
diff --git a/console.c b/console.c
index da28f9f..ca00a5f 100644
--- a/console.c
+++ b/console.c
@@ -112,7 +112,7 @@ panic(char *s)
cli();
cons.locking = 0;
// use lapiccpunum so that we can call panic from mycpu()
- cprintf("cpu %d: panic: ", lapiccpunum());
+ cprintf("lapicid %d: panic: ", lapicid());
cprintf(s);
cprintf("\n");
getcallerpcs(&s, pcs);
diff --git a/defs.h b/defs.h
index c4870d0..82fb982 100644
--- a/defs.h
+++ b/defs.h
@@ -74,7 +74,7 @@ void kbdintr(void);
// lapic.c
void cmostime(struct rtcdate *r);
-int lapiccpunum(void);
+int lapicid(void);
extern volatile uint* lapic;
void lapiceoi(void);
void lapicinit(void);
diff --git a/lapic.c b/lapic.c
index 9a12f17..dc69eb6 100644
--- a/lapic.c
+++ b/lapic.c
@@ -9,7 +9,6 @@
#include "traps.h"
#include "mmu.h"
#include "x86.h"
-#include "proc.h" // ncpu
// Local APIC registers, divided by 4 for use as uint[] indices.
#define ID (0x0020/4) // ID
@@ -98,22 +97,12 @@ lapicinit(void)
lapicw(TPR, 0);
}
-// Should be called with interrupts disabled: the calling thread shouldn't be
-// rescheduled between reading lapic[ID] and checking against cpu array.
int
-lapiccpunum(void)
+lapicid(void)
{
- int apicid, i;
-
if (!lapic)
return 0;
-
- apicid = lapic[ID] >> 24;
- for (i = 0; i < ncpu; ++i) {
- if (cpus[i].apicid == apicid)
- return i;
- }
- panic("unknown apicid\n");
+ return lapic[ID] >> 24;
}
// Acknowledge interrupt.
diff --git a/proc.c b/proc.c
index ca343cb..aac7523 100644
--- a/proc.c
+++ b/proc.c
@@ -32,13 +32,24 @@ cpuid() {
return mycpu()-cpus;
}
-// Must be called with interrupts disabled
+// Must be called with interrupts disabled to avoid the caller being rescheduled
+// between reading lapicid and running through the loop.
struct cpu*
mycpu(void)
{
+ int apicid, i;
+
if(readeflags()&FL_IF)
panic("mycpu called with interrupts enabled\n");
- return &cpus[lapiccpunum()];
+
+ apicid = lapicid();
+ // APIC IDs are not guaranteed to be contiguous. Maybe we should have
+ // a reverse map, or reserve a register to store &cpus[i].
+ for (i = 0; i < ncpu; ++i) {
+ if (cpus[i].apicid == apicid)
+ return &cpus[i];
+ }
+ panic("unknown apicid\n");
}
// Disable interrupts so that we are not rescheduled