* Now using anonymous inode source.
* Thanks to Oleg Nesterov for useful code review and suggestions.
* More comments and suggestions from Arnd Bergmann.
+ * Retrieve multiple signals with one read() call
+ * Attach to the sighand only during read() and poll().
*/
#include <linux/file.h>
#include <linux/list.h>
#include <linux/anon_inodes.h>
#include <linux/signalfd.h>
+#include <linux/syscalls.h>
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 && !ctx->tsk) {
- unlock_task_sighand(lk->tsk, &lk->flags);
- sighand = NULL;
- }
-
- return sighand != NULL;
-}
-
-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;
}
{
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 (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;
}
BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
/*
- * Unused memebers should be zero ...
+ * Unused members should be zero ...
*/
err = __clear_user(uinfo, sizeof(*uinfo));
* If you change siginfo_t structure, please be sure
* this code is fixed accordingly.
*/
- err |= __put_user(kinfo->si_signo, &uinfo->signo);
- err |= __put_user(kinfo->si_errno, &uinfo->err);
- err |= __put_user((short)kinfo->si_code, &uinfo->code);
+ err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
+ err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
+ err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
switch (kinfo->si_code & __SI_MASK) {
case __SI_KILL:
- err |= __put_user(kinfo->si_pid, &uinfo->pid);
- err |= __put_user(kinfo->si_uid, &uinfo->uid);
+ err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
+ err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
break;
case __SI_TIMER:
- err |= __put_user(kinfo->si_tid, &uinfo->tid);
- err |= __put_user(kinfo->si_overrun, &uinfo->overrun);
- err |= __put_user((long)kinfo->si_ptr, &uinfo->svptr);
+ err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
+ err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
+ err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
break;
case __SI_POLL:
- err |= __put_user(kinfo->si_band, &uinfo->band);
- err |= __put_user(kinfo->si_fd, &uinfo->fd);
+ err |= __put_user(kinfo->si_band, &uinfo->ssi_band);
+ err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd);
break;
case __SI_FAULT:
- err |= __put_user((long)kinfo->si_addr, &uinfo->addr);
+ err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr);
#ifdef __ARCH_SI_TRAPNO
- err |= __put_user(kinfo->si_trapno, &uinfo->trapno);
+ err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno);
#endif
break;
case __SI_CHLD:
- err |= __put_user(kinfo->si_pid, &uinfo->pid);
- err |= __put_user(kinfo->si_uid, &uinfo->uid);
- err |= __put_user(kinfo->si_status, &uinfo->status);
- err |= __put_user(kinfo->si_utime, &uinfo->utime);
- err |= __put_user(kinfo->si_stime, &uinfo->stime);
+ err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
+ err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
+ err |= __put_user(kinfo->si_status, &uinfo->ssi_status);
+ err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime);
+ err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime);
break;
case __SI_RT: /* This is not generated by the kernel as of now. */
case __SI_MESGQ: /* But this is */
- err |= __put_user(kinfo->si_pid, &uinfo->pid);
- err |= __put_user(kinfo->si_uid, &uinfo->uid);
- err |= __put_user((long)kinfo->si_ptr, &uinfo->svptr);
+ err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
+ err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
+ err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
break;
- default: /* this is just in case for now ... */
- err |= __put_user(kinfo->si_pid, &uinfo->pid);
- err |= __put_user(kinfo->si_uid, &uinfo->uid);
+ default:
+ /*
+ * This case catches also the signals queued by sigqueue().
+ */
+ err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
+ err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
+ err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
+ err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
break;
}
return err ? -EFAULT: sizeof(*uinfo);
}
+static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
+ int nonblock)
+{
+ ssize_t ret;
+ DECLARE_WAITQUEUE(wait, current);
+
+ spin_lock_irq(¤t->sighand->siglock);
+ ret = dequeue_signal(current, &ctx->sigmask, info);
+ switch (ret) {
+ case 0:
+ if (!nonblock)
+ break;
+ ret = -EAGAIN;
+ default:
+ spin_unlock_irq(¤t->sighand->siglock);
+ return ret;
+ }
+
+ add_wait_queue(¤t->sighand->signalfd_wqh, &wait);
+ for (;;) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ 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();
+ spin_lock_irq(¤t->sighand->siglock);
+ }
+ spin_unlock_irq(¤t->sighand->siglock);
+
+ 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)
{
struct signalfd_ctx *ctx = file->private_data;
- ssize_t res = 0;
- int locked, signo;
+ struct signalfd_siginfo __user *siginfo;
+ int nonblock = file->f_flags & O_NONBLOCK;
+ ssize_t ret, total = 0;
siginfo_t info;
- struct signalfd_lockctx lk;
- DECLARE_WAITQUEUE(wait, current);
- if (count < sizeof(struct signalfd_siginfo))
+ count /= sizeof(struct signalfd_siginfo);
+ if (!count)
return -EINVAL;
- locked = signalfd_lock(ctx, &lk);
- if (!locked)
- return 0;
- res = -EAGAIN;
- signo = dequeue_signal(lk.tsk, &ctx->sigmask, &info);
- if (signo == 0 && !(file->f_flags & O_NONBLOCK)) {
- add_wait_queue(&ctx->wqh, &wait);
- for (;;) {
- set_current_state(TASK_INTERRUPTIBLE);
- signo = dequeue_signal(lk.tsk, &ctx->sigmask, &info);
- if (signo != 0)
- break;
- if (signal_pending(current)) {
- res = -ERESTARTSYS;
- break;
- }
- signalfd_unlock(&lk);
- schedule();
- locked = signalfd_lock(ctx, &lk);
- if (unlikely(!locked)) {
- /*
- * 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.
- */
- res = 0;
- break;
- }
- }
- remove_wait_queue(&ctx->wqh, &wait);
- __set_current_state(TASK_RUNNING);
- }
- if (likely(locked))
- signalfd_unlock(&lk);
- if (likely(signo))
- res = signalfd_copyinfo((struct signalfd_siginfo __user *) buf,
- &info);
- return res;
+ siginfo = (struct signalfd_siginfo __user *) buf;
+ do {
+ ret = signalfd_dequeue(ctx, &info, nonblock);
+ if (unlikely(ret <= 0))
+ break;
+ ret = signalfd_copyinfo(siginfo, &info);
+ if (ret < 0)
+ break;
+ siginfo++;
+ total += ret;
+ nonblock = 1;
+ } while (--count);
+
+ return total ? total: ret;
}
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)))
- return error = -EINVAL;
+ return -EINVAL;
sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
signotset(&sigmask);
if (!ctx)
return -ENOMEM;
- init_waitqueue_head(&ctx->wqh);
ctx->sigmask = sigmask;
- ctx->tsk = current;
-
- 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
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;
}
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