Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal

Pull second pile of signal handling patches from Al Viro:
 "This one is just task_work_add() series + remaining prereqs for it.

  There probably will be another pull request from that tree this
  cycle - at least for helpers, to get them out of the way for per-arch
  fixes remaining in the tree."

Fix trivial conflict in kernel/irq/manage.c: the merge of Andrew's pile
had brought in commit 97fd75b7b8e0 ("kernel/irq/manage.c: use the
pr_foo() infrastructure to prefix printks") which changed one of the
pr_err() calls that this merge moves around.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal:
  keys: kill task_struct->replacement_session_keyring
  keys: kill the dummy key_replace_session_keyring()
  keys: change keyctl_session_to_parent() to use task_work_add()
  genirq: reimplement exit_irq_thread() hook via task_work_add()
  task_work_add: generic process-context callbacks
  avr32: missed _TIF_NOTIFY_RESUME on one of do_notify_resume callers
  parisc: need to check NOTIFY_RESUME when exiting from syscall
  move key_repace_session_keyring() into tracehook_notify_resume()
  TIF_NOTIFY_RESUME is defined on all targets now

6 files changed, 122 insertions, 47 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 80be6ca0cc75..6f3d0ae044b2 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -5,7 +5,7 @@
 obj-y     = fork.o exec_domain.o panic.o printk.o \
             cpu.o exit.o itimer.o time.o softirq.o resource.o \
             sysctl.o sysctl_binary.o capability.o ptrace.o timer.o user.o \
-            signal.o sys.o kmod.o workqueue.o pid.o \
+            signal.o sys.o kmod.o workqueue.o pid.o task_work.o \
             rcupdate.o extable.o params.o posix-timers.o \
             kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
             hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
diff --git a/kernel/cred.c b/kernel/cred.c
index 430557ea488f..de728ac50d82 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -207,13 +207,6 @@ void exit_creds(struct task_struct *tsk)
         validate_creds(cred);
         alter_cred_subscribers(cred, -1);
         put_cred(cred);
-
-        cred = (struct cred *) tsk->replacement_session_keyring;
-        if (cred) {
-                tsk->replacement_session_keyring = NULL;
-                validate_creds(cred);
-                put_cred(cred);
-        }
 }
 
 /**
@@ -396,8 +389,6 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
         struct cred *new;
         int ret;
 
-        p->replacement_session_keyring = NULL;
-
         if (
 #ifdef CONFIG_KEYS
                 !p->cred->thread_keyring &&
diff --git a/kernel/exit.c b/kernel/exit.c
index 6d85655353e9..34867cc5b42a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -946,12 +946,13 @@ void do_exit(long code)
         exit_signals(tsk);  /* sets PF_EXITING */
         /*
          * tsk->flags are checked in the futex code to protect against
-         * an exiting task cleaning up the robust pi futexes.
+         * an exiting task cleaning up the robust pi futexes, and in
+         * task_work_add() to avoid the race with exit_task_work().
          */
         smp_mb();
         raw_spin_unlock_wait(&tsk->pi_lock);
 
-        exit_irq_thread();
+        exit_task_work(tsk);
 
         if (unlikely(in_atomic()))
                 printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
diff --git a/kernel/fork.c b/kernel/fork.c
index c55b61ab6d64..ab5211b9e622 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1415,6 +1415,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
          */
         p->group_leader = p;
         INIT_LIST_HEAD(&p->thread_group);
+        INIT_HLIST_HEAD(&p->task_works);
 
         /* Now that the task is set up, run cgroup callbacks if
          * necessary. We need to run them before the task is visible
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 7c475cd3f6e6..ea0c6c2ae6f7 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -16,6 +16,7 @@
 #include <linux/interrupt.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/task_work.h>
 
 #include "internals.h"
 
@@ -775,11 +776,39 @@ static void wake_threads_waitq(struct irq_desc *desc)
                 wake_up(&desc->wait_for_threads);
 }
 
+static void irq_thread_dtor(struct task_work *unused)
+{
+        struct task_struct *tsk = current;
+        struct irq_desc *desc;
+        struct irqaction *action;
+
+        if (WARN_ON_ONCE(!(current->flags & PF_EXITING)))
+                return;
+
+        action = kthread_data(tsk);
+
+        pr_err("exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n",
+               tsk->comm ? tsk->comm : "", tsk->pid, action->irq);
+
+
+        desc = irq_to_desc(action->irq);
+        /*
+         * If IRQTF_RUNTHREAD is set, we need to decrement
+         * desc->threads_active and wake possible waiters.
+         */
+        if (test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags))
+                wake_threads_waitq(desc);
+
+        /* Prevent a stale desc->threads_oneshot */
+        irq_finalize_oneshot(desc, action);
+}
+
 /*
  * Interrupt handler thread
  */
 static int irq_thread(void *data)
 {
+        struct task_work on_exit_work;
         static const struct sched_param param = {
                 .sched_priority = MAX_USER_RT_PRIO/2,
         };
@@ -795,7 +824,9 @@ static int irq_thread(void *data)
                 handler_fn = irq_thread_fn;
 
         sched_setscheduler(current, SCHED_FIFO, &param);
-        current->irq_thread = 1;
+
+        init_task_work(&on_exit_work, irq_thread_dtor, NULL);
+        task_work_add(current, &on_exit_work, false);
 
         while (!irq_wait_for_interrupt(action)) {
                 irqreturn_t action_ret;
@@ -817,44 +848,11 @@ static int irq_thread(void *data)
          * cannot touch the oneshot mask at this point anymore as
          * __setup_irq() might have given out currents thread_mask
          * again.
-         *
-         * Clear irq_thread. Otherwise exit_irq_thread() would make
-         * fuzz about an active irq thread going into nirvana.
          */
-        current->irq_thread = 0;
+        task_work_cancel(current, irq_thread_dtor);
         return 0;
 }
 
-/*
- * Called from do_exit()
- */
-void exit_irq_thread(void)
-{
-        struct task_struct *tsk = current;
-        struct irq_desc *desc;
-        struct irqaction *action;
-
-        if (!tsk->irq_thread)
-                return;
-
-        action = kthread_data(tsk);
-
-        pr_err("exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n",
-               tsk->comm ? tsk->comm : "", tsk->pid, action->irq);
-
-        desc = irq_to_desc(action->irq);
-
-        /*
-         * If IRQTF_RUNTHREAD is set, we need to decrement
-         * desc->threads_active and wake possible waiters.
-         */
-        if (test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags))
-                wake_threads_waitq(desc);
-
-        /* Prevent a stale desc->threads_oneshot */
-        irq_finalize_oneshot(desc, action);
-}
-
 static void irq_setup_forced_threading(struct irqaction *new)
 {
         if (!force_irqthreads)
diff --git a/kernel/task_work.c b/kernel/task_work.c
new file mode 100644
index 000000000000..82d1c794066d
--- /dev/null
+++ b/kernel/task_work.c
@@ -0,0 +1,84 @@
+#include <linux/spinlock.h>
+#include <linux/task_work.h>
+#include <linux/tracehook.h>
+
+int
+task_work_add(struct task_struct *task, struct task_work *twork, bool notify)
+{
+        unsigned long flags;
+        int err = -ESRCH;
+
+#ifndef TIF_NOTIFY_RESUME
+        if (notify)
+                return -ENOTSUPP;
+#endif
+        /*
+         * We must not insert the new work if the task has already passed
+         * exit_task_work(). We rely on do_exit()->raw_spin_unlock_wait()
+         * and check PF_EXITING under pi_lock.
+         */
+        raw_spin_lock_irqsave(&task->pi_lock, flags);
+        if (likely(!(task->flags & PF_EXITING))) {
+                hlist_add_head(&twork->hlist, &task->task_works);
+                err = 0;
+        }
+        raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+
+        /* test_and_set_bit() implies mb(), see tracehook_notify_resume(). */
+        if (likely(!err) && notify)
+                set_notify_resume(task);
+        return err;
+}
+
+struct task_work *
+task_work_cancel(struct task_struct *task, task_work_func_t func)
+{
+        unsigned long flags;
+        struct task_work *twork;
+        struct hlist_node *pos;
+
+        raw_spin_lock_irqsave(&task->pi_lock, flags);
+        hlist_for_each_entry(twork, pos, &task->task_works, hlist) {
+                if (twork->func == func) {
+                        hlist_del(&twork->hlist);
+                        goto found;
+                }
+        }
+        twork = NULL;
+ found:
+        raw_spin_unlock_irqrestore(&task->pi_lock, flags);
+
+        return twork;
+}
+
+void task_work_run(void)
+{
+        struct task_struct *task = current;
+        struct hlist_head task_works;
+        struct hlist_node *pos;
+
+        raw_spin_lock_irq(&task->pi_lock);
+        hlist_move_list(&task->task_works, &task_works);
+        raw_spin_unlock_irq(&task->pi_lock);
+
+        if (unlikely(hlist_empty(&task_works)))
+                return;
+        /*
+         * We use hlist to save the space in task_struct, but we want fifo.
+         * Find the last entry, the list should be short, then process them
+         * in reverse order.
+         */
+        for (pos = task_works.first; pos->next; pos = pos->next)
+                ;
+
+        for (;;) {
+                struct hlist_node **pprev = pos->pprev;
+                struct task_work *twork = container_of(pos, struct task_work,
+                                                        hlist);
+                twork->func(twork);
+
+                if (pprev == &task_works.first)
+                        break;
+                pos = container_of(pprev, struct hlist_node, next);
+        }
+}