diff --git a/fs/exec.c b/fs/exec.c index c21a8cc0627709db512597ff2af82ab7c094e67d..073b0b8c6d055a3fd947f16fbdbe5552a6bc34c8 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -50,7 +50,6 @@ #include #include #include -#include #include #include @@ -784,7 +783,6 @@ static int de_thread(struct task_struct *tsk) * and we can just re-use it all. */ if (atomic_read(&oldsighand->count) <= 1) { - signalfd_detach(tsk); exit_itimers(sig); return 0; } @@ -923,7 +921,6 @@ static int de_thread(struct task_struct *tsk) sig->flags = 0; no_thread_group: - signalfd_detach(tsk); exit_itimers(sig); if (leader) release_task(leader); diff --git a/fs/signalfd.c b/fs/signalfd.c index a8e293d3003432ff493eff7069f32305fa35006a..aefb0be07942d735de747ad8697834368f8a907a 100644 --- a/fs/signalfd.c +++ b/fs/signalfd.c @@ -11,8 +11,10 @@ * Now using anonymous inode source. * Thanks to Oleg Nesterov for useful code review and suggestions. * More comments and suggestions from Arnd Bergmann. - * Sat May 19, 2007: Davi E. M. Arnaut + * Sat May 19, 2007: Davi E. M. Arnaut * Retrieve multiple signals with one read() call + * Sun Jul 15, 2007: Davide Libenzi + * Attach to the sighand only during read() and poll(). */ #include @@ -27,102 +29,12 @@ #include struct signalfd_ctx { - struct list_head lnk; - wait_queue_head_t wqh; sigset_t sigmask; - struct task_struct *tsk; }; -struct signalfd_lockctx { - struct task_struct *tsk; - unsigned long flags; -}; - -/* - * Tries to acquire the sighand lock. We do not increment the sighand - * use count, and we do not even pin the task struct, so we need to - * do it inside an RCU read lock, and we must be prepared for the - * ctx->tsk going to NULL (in signalfd_deliver()), and for the sighand - * being detached. We return 0 if the sighand has been detached, or - * 1 if we were able to pin the sighand lock. - */ -static int signalfd_lock(struct signalfd_ctx *ctx, struct signalfd_lockctx *lk) -{ - struct sighand_struct *sighand = NULL; - - rcu_read_lock(); - lk->tsk = rcu_dereference(ctx->tsk); - if (likely(lk->tsk != NULL)) - sighand = lock_task_sighand(lk->tsk, &lk->flags); - rcu_read_unlock(); - - if (!sighand) - return 0; - - if (!ctx->tsk) { - unlock_task_sighand(lk->tsk, &lk->flags); - return 0; - } - - if (lk->tsk->tgid == current->tgid) - lk->tsk = current; - - return 1; -} - -static void signalfd_unlock(struct signalfd_lockctx *lk) -{ - unlock_task_sighand(lk->tsk, &lk->flags); -} - -/* - * This must be called with the sighand lock held. - */ -void signalfd_deliver(struct task_struct *tsk, int sig) -{ - struct sighand_struct *sighand = tsk->sighand; - struct signalfd_ctx *ctx, *tmp; - - BUG_ON(!sig); - list_for_each_entry_safe(ctx, tmp, &sighand->signalfd_list, lnk) { - /* - * We use a negative signal value as a way to broadcast that the - * sighand has been orphaned, so that we can notify all the - * listeners about this. Remember the ctx->sigmask is inverted, - * so if the user is interested in a signal, that corresponding - * bit will be zero. - */ - if (sig < 0) { - if (ctx->tsk == tsk) { - ctx->tsk = NULL; - list_del_init(&ctx->lnk); - wake_up(&ctx->wqh); - } - } else { - if (!sigismember(&ctx->sigmask, sig)) - wake_up(&ctx->wqh); - } - } -} - -static void signalfd_cleanup(struct signalfd_ctx *ctx) -{ - struct signalfd_lockctx lk; - - /* - * This is tricky. If the sighand is gone, we do not need to remove - * context from the list, the list itself won't be there anymore. - */ - if (signalfd_lock(ctx, &lk)) { - list_del(&ctx->lnk); - signalfd_unlock(&lk); - } - kfree(ctx); -} - static int signalfd_release(struct inode *inode, struct file *file) { - signalfd_cleanup(file->private_data); + kfree(file->private_data); return 0; } @@ -130,23 +42,15 @@ static unsigned int signalfd_poll(struct file *file, poll_table *wait) { struct signalfd_ctx *ctx = file->private_data; unsigned int events = 0; - struct signalfd_lockctx lk; - poll_wait(file, &ctx->wqh, wait); + poll_wait(file, ¤t->sighand->signalfd_wqh, wait); - /* - * Let the caller get a POLLIN in this case, ala socket recv() when - * the peer disconnects. - */ - if (signalfd_lock(ctx, &lk)) { - if ((lk.tsk == current && - next_signal(&lk.tsk->pending, &ctx->sigmask) > 0) || - next_signal(&lk.tsk->signal->shared_pending, - &ctx->sigmask) > 0) - events |= POLLIN; - signalfd_unlock(&lk); - } else + spin_lock_irq(¤t->sighand->siglock); + if (next_signal(¤t->pending, &ctx->sigmask) || + next_signal(¤t->signal->shared_pending, + &ctx->sigmask)) events |= POLLIN; + spin_unlock_irq(¤t->sighand->siglock); return events; } @@ -219,59 +123,46 @@ static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, int nonblock) { ssize_t ret; - struct signalfd_lockctx lk; DECLARE_WAITQUEUE(wait, current); - if (!signalfd_lock(ctx, &lk)) - return 0; - - ret = dequeue_signal(lk.tsk, &ctx->sigmask, info); + spin_lock_irq(¤t->sighand->siglock); + ret = dequeue_signal(current, &ctx->sigmask, info); switch (ret) { case 0: if (!nonblock) break; ret = -EAGAIN; default: - signalfd_unlock(&lk); + spin_unlock_irq(¤t->sighand->siglock); return ret; } - add_wait_queue(&ctx->wqh, &wait); + add_wait_queue(¤t->sighand->signalfd_wqh, &wait); for (;;) { set_current_state(TASK_INTERRUPTIBLE); - ret = dequeue_signal(lk.tsk, &ctx->sigmask, info); - signalfd_unlock(&lk); + ret = dequeue_signal(current, &ctx->sigmask, info); if (ret != 0) break; if (signal_pending(current)) { ret = -ERESTARTSYS; break; } + spin_unlock_irq(¤t->sighand->siglock); schedule(); - ret = signalfd_lock(ctx, &lk); - if (unlikely(!ret)) { - /* - * Let the caller read zero byte, ala socket - * recv() when the peer disconnect. This test - * must be done before doing a dequeue_signal(), - * because if the sighand has been orphaned, - * the dequeue_signal() call is going to crash - * because ->sighand will be long gone. - */ - break; - } + spin_lock_irq(¤t->sighand->siglock); } + spin_unlock_irq(¤t->sighand->siglock); - remove_wait_queue(&ctx->wqh, &wait); + remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); __set_current_state(TASK_RUNNING); return ret; } /* - * Returns either the size of a "struct signalfd_siginfo", or zero if the - * sighand we are attached to, has been orphaned. The "count" parameter - * must be at least the size of a "struct signalfd_siginfo". + * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative + * error code. The "count" parameter must be at least the size of a + * "struct signalfd_siginfo". */ static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) @@ -287,7 +178,6 @@ static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, return -EINVAL; siginfo = (struct signalfd_siginfo __user *) buf; - do { ret = signalfd_dequeue(ctx, &info, nonblock); if (unlikely(ret <= 0)) @@ -300,7 +190,7 @@ static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, nonblock = 1; } while (--count); - return total ? total : ret; + return total ? total: ret; } static const struct file_operations signalfd_fops = { @@ -309,20 +199,13 @@ static const struct file_operations signalfd_fops = { .read = signalfd_read, }; -/* - * Create a file descriptor that is associated with our signal - * state. We can pass it around to others if we want to, but - * it will always be _our_ signal state. - */ asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemask) { int error; sigset_t sigmask; struct signalfd_ctx *ctx; - struct sighand_struct *sighand; struct file *file; struct inode *inode; - struct signalfd_lockctx lk; if (sizemask != sizeof(sigset_t) || copy_from_user(&sigmask, user_mask, sizeof(sigmask))) @@ -335,17 +218,7 @@ asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemas if (!ctx) return -ENOMEM; - init_waitqueue_head(&ctx->wqh); ctx->sigmask = sigmask; - ctx->tsk = current->group_leader; - - sighand = current->sighand; - /* - * Add this fd to the list of signal listeners. - */ - spin_lock_irq(&sighand->siglock); - list_add_tail(&ctx->lnk, &sighand->signalfd_list); - spin_unlock_irq(&sighand->siglock); /* * When we call this, the initialization must be complete, since @@ -364,23 +237,18 @@ asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemas fput(file); return -EINVAL; } - /* - * We need to be prepared of the fact that the sighand this fd - * is attached to, has been detched. In that case signalfd_lock() - * will return 0, and we'll just skip setting the new mask. - */ - if (signalfd_lock(ctx, &lk)) { - ctx->sigmask = sigmask; - signalfd_unlock(&lk); - } - wake_up(&ctx->wqh); + spin_lock_irq(¤t->sighand->siglock); + ctx->sigmask = sigmask; + spin_unlock_irq(¤t->sighand->siglock); + + wake_up(¤t->sighand->signalfd_wqh); fput(file); } return ufd; err_fdalloc: - signalfd_cleanup(ctx); + kfree(ctx); return error; } diff --git a/include/linux/init_task.h b/include/linux/init_task.h index cab741c2d6033ad937b761852def3fbbf60b763b..f8abfa349ef924344a11b1fd9739e68bd4d72b24 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -86,7 +86,7 @@ extern struct nsproxy init_nsproxy; .count = ATOMIC_INIT(1), \ .action = { { { .sa_handler = NULL, } }, }, \ .siglock = __SPIN_LOCK_UNLOCKED(sighand.siglock), \ - .signalfd_list = LIST_HEAD_INIT(sighand.signalfd_list), \ + .signalfd_wqh = __WAIT_QUEUE_HEAD_INITIALIZER(sighand.signalfd_wqh), \ } extern struct group_info init_groups; diff --git a/include/linux/sched.h b/include/linux/sched.h index 3de79016f2a669dbbb5bd16395d3458032be2b86..a01ac6dd5f5e1c07d9a54a8f879512db2eac3905 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -438,7 +438,7 @@ struct sighand_struct { atomic_t count; struct k_sigaction action[_NSIG]; spinlock_t siglock; - struct list_head signalfd_list; + wait_queue_head_t signalfd_wqh; }; struct pacct_struct { diff --git a/include/linux/signalfd.h b/include/linux/signalfd.h index 5104294956906c038e4359ab4e37c35632e2e478..4c9ff0910ae01d39f691a23c9acf5d1db48b06d2 100644 --- a/include/linux/signalfd.h +++ b/include/linux/signalfd.h @@ -45,49 +45,17 @@ struct signalfd_siginfo { #ifdef CONFIG_SIGNALFD /* - * Deliver the signal to listening signalfd. This must be called - * with the sighand lock held. Same are the following that end up - * calling signalfd_deliver(). - */ -void signalfd_deliver(struct task_struct *tsk, int sig); - -/* - * No need to fall inside signalfd_deliver() if no signal listeners - * are available. + * Deliver the signal to listening signalfd. */ static inline void signalfd_notify(struct task_struct *tsk, int sig) { - if (unlikely(!list_empty(&tsk->sighand->signalfd_list))) - signalfd_deliver(tsk, sig); -} - -/* - * The signal -1 is used to notify the signalfd that the sighand - * is on its way to be detached. - */ -static inline void signalfd_detach_locked(struct task_struct *tsk) -{ - if (unlikely(!list_empty(&tsk->sighand->signalfd_list))) - signalfd_deliver(tsk, -1); -} - -static inline void signalfd_detach(struct task_struct *tsk) -{ - struct sighand_struct *sighand = tsk->sighand; - - if (unlikely(!list_empty(&sighand->signalfd_list))) { - spin_lock_irq(&sighand->siglock); - signalfd_deliver(tsk, -1); - spin_unlock_irq(&sighand->siglock); - } + if (unlikely(waitqueue_active(&tsk->sighand->signalfd_wqh))) + wake_up(&tsk->sighand->signalfd_wqh); } #else /* CONFIG_SIGNALFD */ -#define signalfd_deliver(t, s) do { } while (0) -#define signalfd_notify(t, s) do { } while (0) -#define signalfd_detach_locked(t) do { } while (0) -#define signalfd_detach(t) do { } while (0) +static inline void signalfd_notify(struct task_struct *tsk, int sig) { } #endif /* CONFIG_SIGNALFD */ diff --git a/kernel/exit.c b/kernel/exit.c index 06b24b3aa370c69577012023b12573d4c7624d19..993369ee94d1ebb8d4c7675a821e90abf8a1737e 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -24,7 +24,6 @@ #include #include #include -#include #include #include #include @@ -86,14 +85,6 @@ static void __exit_signal(struct task_struct *tsk) sighand = rcu_dereference(tsk->sighand); spin_lock(&sighand->siglock); - /* - * Notify that this sighand has been detached. This must - * be called with the tsk->sighand lock held. Also, this - * access tsk->sighand internally, so it must be called - * before tsk->sighand is reset. - */ - signalfd_detach_locked(tsk); - posix_cpu_timers_exit(tsk); if (atomic_dec_and_test(&sig->count)) posix_cpu_timers_exit_group(tsk); diff --git a/kernel/fork.c b/kernel/fork.c index 7332e236d3676153dc9f40c1a78848e6e2810632..33f12f48684a0053a82d72506c1d7ec1e7ca6a15 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1438,7 +1438,7 @@ static void sighand_ctor(void *data, struct kmem_cache *cachep, struct sighand_struct *sighand = data; spin_lock_init(&sighand->siglock); - INIT_LIST_HEAD(&sighand->signalfd_list); + init_waitqueue_head(&sighand->signalfd_wqh); } void __init proc_caches_init(void) diff --git a/kernel/signal.c b/kernel/signal.c index 3169bed0b4d0e44166b37c48ed663d516a9ccba5..9fb91a32eddaddfd47d09cb0aa66586a5635a39e 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -378,8 +378,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info) /* We only dequeue private signals from ourselves, we don't let * signalfd steal them */ - if (likely(tsk == current)) - signr = __dequeue_signal(&tsk->pending, mask, info); + signr = __dequeue_signal(&tsk->pending, mask, info); if (!signr) { signr = __dequeue_signal(&tsk->signal->shared_pending, mask, info); @@ -407,8 +406,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info) } } } - if (likely(tsk == current)) - recalc_sigpending(); + recalc_sigpending(); if (signr && unlikely(sig_kernel_stop(signr))) { /* * Set a marker that we have dequeued a stop signal. Our @@ -425,7 +423,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info) if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT)) tsk->signal->flags |= SIGNAL_STOP_DEQUEUED; } - if (signr && likely(tsk == current) && + if (signr && ((info->si_code & __SI_MASK) == __SI_TIMER) && info->si_sys_private){ /*