diff options
| -rw-r--r-- | bio.c | 45 | ||||
| -rw-r--r-- | buf.h | 7 | ||||
| -rw-r--r-- | defs.h | 5 | ||||
| -rw-r--r-- | file.c | 6 | ||||
| -rw-r--r-- | file.h | 6 | ||||
| -rw-r--r-- | fs.c | 32 | ||||
| -rw-r--r-- | ide.c | 2 | ||||
| -rw-r--r-- | log.c | 14 | ||||
| -rw-r--r-- | pipe.c | 2 | ||||
| -rw-r--r-- | spinlock.c | 42 | ||||
| -rw-r--r-- | spinlock.h | 7 | ||||
| -rw-r--r-- | sysfile.c | 1 |
12 files changed, 106 insertions, 63 deletions
@@ -13,9 +13,7 @@ // * Only one process at a time can use a buffer, // so do not keep them longer than necessary. // -// The implementation uses three state flags internally: -// * B_BUSY: the block has been returned from bread -// and has not been passed back to brelse. +// The implementation uses two state flags internally: // * B_VALID: the buffer data has been initialized // with the associated disk block contents. // * B_DIRTY: the buffer data has been modified @@ -51,6 +49,8 @@ binit(void) b->next = bcache.head.next; b->prev = &bcache.head; b->dev = -1; + initlock(&b->lock, "buf"); + initsleeplock(&b->sleeplock); bcache.head.next->prev = b; bcache.head.next = b; } @@ -58,42 +58,43 @@ binit(void) // Look through buffer cache for sector on device dev. // If not found, allocate fresh block. -// In either case, return locked buffer. +// In either case, return sleep-locked buffer. static struct buf* bget(uint dev, uint sector) { struct buf *b; acquire(&bcache.lock); - - loop: // Try for cached block. for(b = bcache.head.next; b != &bcache.head; b = b->next){ + acquire(&b->lock); if(b->dev == dev && b->sector == sector){ - if(!(b->flags & B_BUSY)){ - b->flags |= B_BUSY; - release(&bcache.lock); - return b; - } - sleep(b, &bcache.lock); - goto loop; + release(&bcache.lock); + acquire_sleeplock(&b->sleeplock, &b->lock); + release(&b->lock); + return b; } + release(&b->lock); } // Allocate fresh block. for(b = bcache.head.prev; b != &bcache.head; b = b->prev){ - if((b->flags & B_BUSY) == 0){ + acquire(&b->lock); + if (!acquired_sleeplock(&b->sleeplock)) { + release(&bcache.lock); b->dev = dev; b->sector = sector; - b->flags = B_BUSY; - release(&bcache.lock); + b->flags = 0; + acquire_sleeplock(&b->sleeplock, &b->lock); + release(&b->lock); return b; } + release(&b->lock); } panic("bget: no buffers"); } -// Return a B_BUSY buf with the contents of the indicated disk sector. +// Return a locked buf with the contents of the indicated disk sector. struct buf* bread(uint dev, uint sector) { @@ -109,7 +110,7 @@ bread(uint dev, uint sector) void bwrite(struct buf *b) { - if((b->flags & B_BUSY) == 0) + if(!acquired_sleeplock(&b->sleeplock)) panic("bwrite"); b->flags |= B_DIRTY; iderw(b); @@ -119,11 +120,11 @@ bwrite(struct buf *b) void brelse(struct buf *b) { - if((b->flags & B_BUSY) == 0) + if(!acquired_sleeplock(&b->sleeplock)) panic("brelse"); acquire(&bcache.lock); - + acquire(&b->lock); b->next->prev = b->prev; b->prev->next = b->next; b->next = bcache.head.next; @@ -131,8 +132,8 @@ brelse(struct buf *b) bcache.head.next->prev = b; bcache.head.next = b; - b->flags &= ~B_BUSY; - wakeup(b); + release_sleeplock(&b->sleeplock); + release(&b->lock); release(&bcache.lock); } @@ -2,12 +2,13 @@ struct buf { int flags; uint dev; uint sector; + struct spinlock lock; + struct sleeplock sleeplock; struct buf *prev; // LRU cache list struct buf *next; struct buf *qnext; // disk queue uchar data[512]; }; -#define B_BUSY 0x1 // buffer is locked by some process -#define B_VALID 0x2 // buffer has been read from disk -#define B_DIRTY 0x4 // buffer needs to be written to disk +#define B_VALID 0x1 // buffer has been read from disk +#define B_DIRTY 0x2 // buffer needs to be written to disk @@ -5,6 +5,7 @@ struct inode; struct pipe; struct proc; struct spinlock; +struct sleeplock; struct stat; struct superblock; @@ -129,6 +130,10 @@ void initlock(struct spinlock*, char*); void release(struct spinlock*); void pushcli(void); void popcli(void); +void initsleeplock(struct sleeplock*); +void acquire_sleeplock(struct sleeplock*,struct spinlock*); +void release_sleeplock(struct sleeplock*); +int acquired_sleeplock(struct sleeplock*); // string.c int memcmp(const void*, const void*, uint); @@ -2,8 +2,8 @@ #include "defs.h" #include "param.h" #include "fs.h" -#include "file.h" #include "spinlock.h" +#include "file.h" struct devsw devsw[NDEV]; struct { @@ -133,7 +133,8 @@ filewrite(struct file *f, char *addr, int n) begin_trans(); ilock(f->ip); - r = writei(f->ip, addr + i, f->off, n1); + if ((r = writei(f->ip, addr + i, f->off, n1)) > 0) + f->off += r; iunlock(f->ip); commit_trans(); @@ -141,7 +142,6 @@ filewrite(struct file *f, char *addr, int n) break; if(r != n1) panic("short filewrite"); - f->off += r; i += r; } return i == n ? n : -1; @@ -15,7 +15,9 @@ struct inode { uint dev; // Device number uint inum; // Inode number int ref; // Reference count - int flags; // I_BUSY, I_VALID + int flags; // I_VALID + struct spinlock lock; + struct sleeplock sleeplock; short type; // copy of disk inode short major; @@ -25,10 +27,8 @@ struct inode { uint addrs[NDIRECT+1]; }; -#define I_BUSY 0x1 #define I_VALID 0x2 - // device implementations struct devsw { @@ -113,11 +113,8 @@ bfree(int dev, uint b) // It is an error to use an inode without holding a reference to it. // // Processes are only allowed to read and write inode -// metadata and contents when holding the inode's lock, -// represented by the I_BUSY flag in the in-memory copy. -// Because inode locks are held during disk accesses, -// they are implemented using a flag rather than with -// spin locks. Callers are responsible for locking +// metadata and contents when holding the inode's sleeplock. +// Callers are responsible for locking // inodes before passing them to routines in this file; leaving // this responsibility with the caller makes it possible for them // to create arbitrarily-sized atomic operations. @@ -216,6 +213,7 @@ iget(uint dev, uint inum) ip->inum = inum; ip->ref = 1; ip->flags = 0; + initsleeplock(&ip->sleeplock); release(&icache.lock); return ip; @@ -232,7 +230,7 @@ idup(struct inode *ip) return ip; } -// Lock the given inode. +// Acquire the sleeplock for a given inode. void ilock(struct inode *ip) { @@ -243,9 +241,7 @@ ilock(struct inode *ip) panic("ilock"); acquire(&icache.lock); - while(ip->flags & I_BUSY) - sleep(ip, &icache.lock); - ip->flags |= I_BUSY; + acquire_sleeplock(&ip->sleeplock, &icache.lock); release(&icache.lock); if(!(ip->flags & I_VALID)){ @@ -268,12 +264,11 @@ ilock(struct inode *ip) void iunlock(struct inode *ip) { - if(ip == 0 || !(ip->flags & I_BUSY) || ip->ref < 1) + if(ip == 0 || !acquired_sleeplock(&ip->sleeplock) || ip->ref < 1) panic("iunlock"); acquire(&icache.lock); - ip->flags &= ~I_BUSY; - wakeup(ip); + release_sleeplock(&ip->sleeplock); release(&icache.lock); } @@ -284,14 +279,15 @@ iput(struct inode *ip) acquire(&icache.lock); if(ip->ref == 1 && (ip->flags & I_VALID) && ip->nlink == 0){ // inode is no longer used: truncate and free inode. - if(ip->flags & I_BUSY) + if(acquired_sleeplock(&ip->sleeplock)) panic("iput busy"); - ip->flags |= I_BUSY; + acquire_sleeplock(&ip->sleeplock, &icache.lock); release(&icache.lock); itrunc(ip); ip->type = 0; iupdate(ip); acquire(&icache.lock); + release_sleeplock(&ip->sleeplock); ip->flags = 0; wakeup(ip); } @@ -433,10 +429,14 @@ writei(struct inode *ip, char *src, uint off, uint n) return devsw[ip->major].write(ip, src, n); } - if(off > ip->size || off + n < off) + if(off > ip->size || off + n < off) { + panic("writei1"); return -1; - if(off + n > MAXFILE*BSIZE) + } + if(off + n > MAXFILE*BSIZE) { + panic("writei2"); return -1; + } for(tot=0; tot<n; tot+=m, off+=m, src+=m){ bp = bread(ip->dev, bmap(ip, off/BSIZE)); @@ -127,7 +127,7 @@ iderw(struct buf *b) { struct buf **pp; - if(!(b->flags & B_BUSY)) + if(!acquired_sleeplock(&b->sleeplock)) panic("iderw: buf not busy"); if((b->flags & (B_VALID|B_DIRTY)) == B_VALID) panic("iderw: nothing to do"); @@ -43,9 +43,9 @@ struct logheader { struct { struct spinlock lock; + struct sleeplock sleeplock; int start; int size; - int intrans; int dev; struct logheader lh; } log; @@ -60,6 +60,7 @@ initlog(void) struct superblock sb; initlock(&log.lock, "log"); + initsleeplock(&log.sleeplock); readsb(ROOTDEV, &sb); log.start = sb.size - sb.nlog; log.size = sb.nlog; @@ -133,10 +134,7 @@ void begin_trans(void) { acquire(&log.lock); - while (log.intrans) { - sleep(&log, &log.lock); - } - log.intrans = 1; + acquire_sleeplock(&log.sleeplock, &log.lock); release(&log.lock); } @@ -149,10 +147,8 @@ commit_trans(void) log.lh.n = 0; write_head(); // Reclaim log } - acquire(&log.lock); - log.intrans = 0; - wakeup(&log); + release_sleeplock(&log.sleeplock); release(&log.lock); } @@ -171,7 +167,7 @@ log_write(struct buf *b) if (log.lh.n >= LOGSIZE || log.lh.n >= log.size - 1) panic("too big a transaction"); - if (!log.intrans) + if (!acquired_sleeplock(&log.sleeplock)) panic("write outside of trans"); // cprintf("log_write: %d %d\n", b->sector, log.lh.n); @@ -4,8 +4,8 @@ #include "mmu.h" #include "proc.h" #include "fs.h" -#include "file.h" #include "spinlock.h" +#include "file.h" #define PIPESIZE 512 @@ -17,10 +17,9 @@ initlock(struct spinlock *lk, char *name) lk->cpu = 0; } -// Acquire the lock. -// Loops (spins) until the lock is acquired. -// Holding a lock for a long time may cause -// other CPUs to waste time spinning to acquire it. +// Acquire a spin lock. Loops (spins) until the lock is acquired. +// Holding a lock for a long time may cause other CPUs to waste time spinning to acquire it. +// Spinlocks shouldn't be held across sleep(); for those cases, use sleeplocks. void acquire(struct spinlock *lk) { @@ -115,3 +114,38 @@ popcli(void) sti(); } +void +initsleeplock(struct sleeplock *l) +{ + l->locked = 0; +} + +// Grab the sleeplock that is protected by spinl. Sleeplocks allow a process to lock +// a data structure for long times, including across sleeps. Other processes that try +// to acquire a sleeplock will be put to sleep when another process hold the sleeplock. +// To update status of the sleeplock atomically, the caller must hold spinl +void +acquire_sleeplock(struct sleeplock *sleepl, struct spinlock *spinl) +{ + while (sleepl->locked) { + sleep(sleepl, spinl); + } + sleepl->locked = 1; +} + +// Release the sleeplock that is protected by a spin lock +// Caller must hold the spinlock that protects the sleeplock +void +release_sleeplock(struct sleeplock *sleepl) +{ + sleepl->locked = 0; + wakeup(sleepl); +} + +// Is the sleeplock acquired? +// Caller must hold the spinlock that protects the sleeplock +int +acquired_sleeplock(struct sleeplock *sleepl) +{ + return sleepl->locked; +} @@ -1,4 +1,4 @@ -// Mutual exclusion lock. +// Mutual exclusion lock for short code fragments struct spinlock { uint locked; // Is the lock held? @@ -9,3 +9,8 @@ struct spinlock { // that locked the lock. }; +// Lock that maybe held across sleeps +struct sleeplock { + uint locked; // Is the lock held? +}; + @@ -5,6 +5,7 @@ #include "mmu.h" #include "proc.h" #include "fs.h" +#include "spinlock.h" #include "file.h" #include "fcntl.h" |