diff options
| -rw-r--r-- | bootasm.S | 2 | ||||
| -rw-r--r-- | buf.h | 4 | ||||
| -rw-r--r-- | fs.c | 2 | ||||
| -rw-r--r-- | init.c | 4 | ||||
| -rw-r--r-- | kalloc.c | 2 | ||||
| -rw-r--r-- | main.c | 4 | ||||
| -rw-r--r-- | spinlock.c | 13 |
7 files changed, 15 insertions, 16 deletions
@@ -5,7 +5,7 @@ .set CR0_PE_ON,0x1 # protected mode enable flag ######################################################################### -# ENTRY POINT +# ENTRY POINT for the bootstrap processor # This code should be stored in the first sector of the hard disk. # After the BIOS initializes the hardware on startup or system reset, # it loads this code at physical address 0x7c00 - 0x7d00 (512 bytes). @@ -6,5 +6,5 @@ struct buf { struct buf *next; uchar data[512]; }; -#define B_BUSY 0x1 -#define B_VALID 0x2 +#define B_BUSY 0x1 // buffer is locked by some process +#define B_VALID 0x2 // buffer contains the data of the sector @@ -160,7 +160,7 @@ iget(uint dev, uint inum) return nip; } -// Copy ip->d, which has changed, to disk. +// Copy inode in memory, which has changed, to disk. // Caller must have locked ip. void iupdate(struct inode *ip) @@ -17,8 +17,8 @@ main(void) mknod("console", T_DEV, 1, 1); open("console", O_RDWR); } - dup(0); - dup(0); + dup(0); // stdout + dup(0); // stderr for(;;){ pid = fork(); @@ -35,7 +35,7 @@ kinit(void) initlock(&kalloc_lock, "kalloc"); start = (char*) &end; start = (char*) (((uint)start + PAGE) & ~(PAGE-1)); - mem = 256; // assume 256 pages of RAM + mem = 256; // assume computer has 256 pages of RAM cprintf("mem = %d\n", mem * PAGE); kfree(start, mem * PAGE); } @@ -15,7 +15,7 @@ extern uchar _binary__init_start[], _binary__init_size[]; void process0(); -// CPU 0 starts running C code here. +// Bootstrap processor starts running C code here. // This is called main0 not main so that it can have // a void return type. Gcc can't handle functions named // main that don't return int. Really. @@ -28,7 +28,7 @@ main0(void) // clear BSS memset(edata, 0, end - edata); - // switch to cpu0's cpu stack + // switch to bootstrap processor's stack asm volatile("movl %0, %%esp" : : "r" (cpus[0].mpstack + MPSTACK - 32)); asm volatile("movl %0, %%ebp" : : "r" (cpus[0].mpstack + MPSTACK)); @@ -51,10 +51,9 @@ acquire(struct spinlock *lock) while(cmpxchg(0, 1, &lock->locked) == 1) ; - // Now that lock is acquired, make sure - // we wait for all pending writes from other - // processors. - cpuid(0, 0, 0, 0, 0); // memory barrier + // Serialize instructions: now that lock is acquired, make sure + // we wait for all pending writes from other processors. + cpuid(0, 0, 0, 0, 0); // memory barrier (see Ch 7 of IA-32 manual, vol 3) // Record info about lock acquisition for debugging. // The +10 is only so that we can tell the difference @@ -74,9 +73,9 @@ release(struct spinlock *lock) lock->pcs[0] = 0; lock->cpu = 0xffffffff; - // Before unlocking the lock, make sure to flush - // any pending memory writes from this processor. - cpuid(0, 0, 0, 0, 0); // memory barrier + // Serialize instructions: before unlocking the lock, make sure + // to flush any pending memory writes from this processor. + cpuid(0, 0, 0, 0, 0); // memory barrier (see Ch 7 of IA-32 manual, vol 3) lock->locked = 0; if(--cpus[cpu()].nlock == 0) |