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authorRobert Morris <[email protected]>2010-08-05 21:16:55 -0400
committerRobert Morris <[email protected]>2010-08-05 21:16:55 -0400
commit1afc9d3fcaa7c5992659bb8b69f639b746dda2bc (patch)
treee60a41707282ba0ef2c1e00b9cba97bb71339284 /main.c
parentc99599784e950169d85bf1e4446e7dbfb1a40f59 (diff)
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add some comments
find out the hard way why user and kernel must have separate segment descriptors
Diffstat (limited to 'main.c')
-rw-r--r--main.c22
1 files changed, 12 insertions, 10 deletions
diff --git a/main.c b/main.c
index 8be66e3..a6088cb 100644
--- a/main.c
+++ b/main.c
@@ -16,13 +16,13 @@ main(void)
{
mpinit(); // collect info about this machine
lapicinit(mpbcpu());
- ksegment();
+ ksegment(); // set up segments
picinit(); // interrupt controller
ioapicinit(); // another interrupt controller
consoleinit(); // I/O devices & their interrupts
uartinit(); // serial port
- pminit(); // physical memory for kernel
- jkstack(); // Jump to mainc on a properly-allocated stack
+ pminit(); // discover how much memory there is
+ jkstack(); // call mainc() on a properly-allocated stack
}
void
@@ -41,7 +41,7 @@ void
mainc(void)
{
cprintf("\ncpu%d: starting xv6\n\n", cpu->id);
- kvmalloc(); // allocate the kernel page table
+ kvmalloc(); // initialze the kernel page table
pinit(); // process table
tvinit(); // trap vectors
binit(); // buffer cache
@@ -57,8 +57,9 @@ mainc(void)
mpmain();
}
-// Bootstrap processor gets here after setting up the hardware.
-// Additional processors start here.
+// Common CPU setup code.
+// Bootstrap CPU comes here from mainc().
+// Other CPUs jump here from bootother.S.
static void
mpmain(void)
{
@@ -66,11 +67,11 @@ mpmain(void)
ksegment();
lapicinit(cpunum());
}
- vminit(); // Run with paging on each processor
+ vminit(); // turn on paging
cprintf("cpu%d: starting\n", cpu->id);
- idtinit();
+ idtinit(); // load idt register
xchg(&cpu->booted, 1);
- scheduler();
+ scheduler(); // start running processes
}
static void
@@ -85,6 +86,7 @@ bootothers(void)
// placed the start of bootother.S there.
code = (uchar *) 0x7000;
memmove(code, _binary_bootother_start, (uint)_binary_bootother_size);
+
for(c = cpus; c < cpus+ncpu; c++){
if(c == cpus+cpunum()) // We've started already.
continue;
@@ -95,7 +97,7 @@ bootothers(void)
*(void**)(code-8) = mpmain;
lapicstartap(c->id, (uint)code);
- // Wait for cpu to get through bootstrap.
+ // Wait for cpu to finish mpmain()
while(c->booted == 0)
;
}