diff options
| -rw-r--r-- | fs/eventfd.c | 20 | ||||
| -rw-r--r-- | include/linux/eventfd.h | 12 |
2 files changed, 22 insertions, 10 deletions
diff --git a/fs/eventfd.c b/fs/eventfd.c index 5de2c2d..91c0829 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -28,6 +28,7 @@ struct eventfd_ctx { * issue a wakeup. */ __u64 count; + unsigned int flags; }; /* @@ -87,22 +88,20 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, { struct eventfd_ctx *ctx = file->private_data; ssize_t res; - __u64 ucnt; + __u64 ucnt = 0; DECLARE_WAITQUEUE(wait, current); if (count < sizeof(ucnt)) return -EINVAL; spin_lock_irq(&ctx->wqh.lock); res = -EAGAIN; - ucnt = ctx->count; - if (ucnt > 0) + if (ctx->count > 0) res = sizeof(ucnt); else if (!(file->f_flags & O_NONBLOCK)) { __add_wait_queue(&ctx->wqh, &wait); for (res = 0;;) { set_current_state(TASK_INTERRUPTIBLE); if (ctx->count > 0) { - ucnt = ctx->count; res = sizeof(ucnt); break; } @@ -117,8 +116,9 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, __remove_wait_queue(&ctx->wqh, &wait); __set_current_state(TASK_RUNNING); } - if (res > 0) { - ctx->count = 0; + if (likely(res > 0)) { + ucnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count; + ctx->count -= ucnt; if (waitqueue_active(&ctx->wqh)) wake_up_locked(&ctx->wqh); } @@ -166,7 +166,7 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c __remove_wait_queue(&ctx->wqh, &wait); __set_current_state(TASK_RUNNING); } - if (res > 0) { + if (likely(res > 0)) { ctx->count += ucnt; if (waitqueue_active(&ctx->wqh)) wake_up_locked(&ctx->wqh); @@ -207,7 +207,7 @@ SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags) BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC); BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK); - if (flags & ~(EFD_CLOEXEC | EFD_NONBLOCK)) + if (flags & ~EFD_FLAGS_SET) return -EINVAL; ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); @@ -216,13 +216,14 @@ SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags) init_waitqueue_head(&ctx->wqh); ctx->count = count; + ctx->flags = flags; /* * When we call this, the initialization must be complete, since * anon_inode_getfd() will install the fd. */ fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx, - flags & (O_CLOEXEC | O_NONBLOCK)); + flags & EFD_SHARED_FCNTL_FLAGS); if (fd < 0) kfree(ctx); return fd; @@ -232,3 +233,4 @@ SYSCALL_DEFINE1(eventfd, unsigned int, count) { return sys_eventfd2(count, 0); } + diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h index a667637..f45a8ae 100644 --- a/include/linux/eventfd.h +++ b/include/linux/eventfd.h @@ -13,10 +13,20 @@ /* For O_CLOEXEC and O_NONBLOCK */ #include <linux/fcntl.h> -/* Flags for eventfd2. */ +/* + * CAREFUL: Check include/asm-generic/fcntl.h when defining + * new flags, since they might collide with O_* ones. We want + * to re-use O_* flags that couldn't possibly have a meaning + * from eventfd, in order to leave a free define-space for + * shared O_* flags. + */ +#define EFD_SEMAPHORE (1 << 0) #define EFD_CLOEXEC O_CLOEXEC #define EFD_NONBLOCK O_NONBLOCK +#define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK) +#define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE) + struct file *eventfd_fget(int fd); int eventfd_signal(struct file *file, int n); |