diff options
| -rw-r--r-- | kernel/kalloc.c | 4 | ||||
| -rw-r--r-- | kernel/spinlock.c | 9 | ||||
| -rw-r--r-- | user/usertests.c | 39 |
3 files changed, 47 insertions, 5 deletions
diff --git a/kernel/kalloc.c b/kernel/kalloc.c index afadb02..d72e0ab 100644 --- a/kernel/kalloc.c +++ b/kernel/kalloc.c @@ -55,8 +55,9 @@ kfree(void *pa) // Fill with junk to catch dangling refs. memset(pa, 1, PGSIZE); - acquire(&kmem.lock); r = (struct run*)pa; + + acquire(&kmem.lock); r->next = kmem.freelist; kmem.freelist = r; release(&kmem.lock); @@ -75,6 +76,7 @@ kalloc(void) if(r) kmem.freelist = r->next; release(&kmem.lock); + if(r) memset((char*)r, 5, PGSIZE); // fill with junk return (void*)r; diff --git a/kernel/spinlock.c b/kernel/spinlock.c index 52bd504..83512bb 100644 --- a/kernel/spinlock.c +++ b/kernel/spinlock.c @@ -25,7 +25,7 @@ acquire(struct spinlock *lk) if(holding(lk)) panic("acquire"); - // On RISC-V, this turns into an atomic swap: + // On RISC-V, sync_lock_test_and_set turns into an atomic swap: // a5 = 1 // s1 = &lk->locked // amoswap.w.aq a5, a5, (s1) @@ -57,9 +57,10 @@ release(struct spinlock *lk) __sync_synchronize(); // Release the lock, equivalent to lk->locked = 0. - // This code can't use a C assignment, since it might - // not be atomic. - // On RISC-V, this turns into an atomic swap: + // This code doesn't use a C assignment, since the C standard + // implies that an assignment might be implemented with + // multiple store instructions. + // On RISC-V, sync_lock_release turns into an atomic swap: // s1 = &lk->locked // amoswap.w zero, zero, (s1) __sync_lock_release(&lk->locked); diff --git a/user/usertests.c b/user/usertests.c index 9d46b1a..5cc5099 100644 --- a/user/usertests.c +++ b/user/usertests.c @@ -506,6 +506,44 @@ twochildren(void) printf(1, "twochildren ok\n"); } +// concurrent forks to try to expose locking bugs. +void +forkfork(void) +{ + int ppid = getpid(); + + printf(1, "forkfork test\n"); + + for(int i = 0; i < 2; i++){ + int pid = fork(); + if(pid < 0){ + printf(1, "fork failed"); + exit(); + } + if(pid == 0){ + for(int j = 0; j < 200; j++){ + int pid1 = fork(); + if(pid1 < 0){ + printf(1, "fork failed\n"); + kill(ppid); + exit(); + } + if(pid1 == 0){ + exit(); + } + wait(); + } + exit(); + } + } + + for(int i = 0; i < 2; i++){ + wait(); + } + + printf(1, "forkfork ok\n"); +} + void forkforkfork(void) { @@ -1858,6 +1896,7 @@ main(int argc, char *argv[]) reparent(); twochildren(); + forkfork(); forkforkfork(); argptest(); |