Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull core signal handling updates from Eric Biederman:
 "It was observed that a periodic timer in combination with a
  sufficiently expensive fork could prevent fork from every completing.
  This contains the changes to remove the need for that restart.

  This set of changes is split into several parts:

   - The first part makes PIDTYPE_TGID a proper pid type instead
     something only for very special cases. The part starts using
     PIDTYPE_TGID enough so that in __send_signal where signals are
     actually delivered we know if the signal is being sent to a a group
     of processes or just a single process.

   - With that prep work out of the way the logic in fork is modified so
     that fork logically makes signals received while it is running
     appear to be received after the fork completes"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (22 commits)
  signal: Don't send signals to tasks that don't exist
  signal: Don't restart fork when signals come in.
  fork: Have new threads join on-going signal group stops
  fork: Skip setting TIF_SIGPENDING in ptrace_init_task
  signal: Add calculate_sigpending()
  fork: Unconditionally exit if a fatal signal is pending
  fork: Move and describe why the code examines PIDNS_ADDING
  signal: Push pid type down into complete_signal.
  signal: Push pid type down into __send_signal
  signal: Push pid type down into send_signal
  signal: Pass pid type into do_send_sig_info
  signal: Pass pid type into send_sigio_to_task & send_sigurg_to_task
  signal: Pass pid type into group_send_sig_info
  signal: Pass pid and pid type into send_sigqueue
  posix-timers: Noralize good_sigevent
  signal: Use PIDTYPE_TGID to clearly store where file signals will be sent
  pid: Implement PIDTYPE_TGID
  pids: Move the pgrp and session pid pointers from task_struct to signal_struct
  kvm: Don't open code task_pid in kvm_vcpu_ioctl
  pids: Compute task_tgid using signal->leader_pid
  ...

6 files changed, 58 insertions, 50 deletions

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index a454b8aeb938..a7083a45a26c 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -46,15 +46,6 @@ extern struct cred init_cred;
 #define INIT_CPU_TIMERS(s)
 #endif
 
-#define INIT_PID_LINK(type) 					\
-{								\
-	.node = {						\
-		.next = NULL,					\
-		.pprev = NULL,					\
-	},							\
-	.pid = &init_struct_pid,				\
-}
-
 #define INIT_TASK_COMM "swapper"
 
 /* Attach to the init_task data structure for proper alignment */
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 7633d55d9a24..14a9a39da9c7 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -7,11 +7,10 @@
 enum pid_type
 {
 	PIDTYPE_PID,
+	PIDTYPE_TGID,
 	PIDTYPE_PGID,
 	PIDTYPE_SID,
 	PIDTYPE_MAX,
-	/* only valid to __task_pid_nr_ns() */
-	__PIDTYPE_TGID
 };
 
 /*
@@ -67,12 +66,6 @@ struct pid
 
 extern struct pid init_struct_pid;
 
-struct pid_link
-{
-	struct hlist_node node;
-	struct pid *pid;
-};
-
 static inline struct pid *get_pid(struct pid *pid)
 {
 	if (pid)
@@ -177,7 +170,7 @@ pid_t pid_vnr(struct pid *pid);
 	do {								\
 		if ((pid) != NULL)					\
 			hlist_for_each_entry_rcu((task),		\
-				&(pid)->tasks[type], pids[type].node) {
+				&(pid)->tasks[type], pid_links[type]) {
 
 			/*
 			 * Both old and new leaders may be attached to
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 037bf0ef1ae9..4f36431c380b 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -214,8 +214,6 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
 			task_set_jobctl_pending(child, JOBCTL_TRAP_STOP);
 		else
 			sigaddset(&child->pending.signal, SIGSTOP);
-
-		set_tsk_thread_flag(child, TIF_SIGPENDING);
 	}
 	else
 		child->ptracer_cred = NULL;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 789923fbee3a..00de3e950dd4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -779,7 +779,8 @@ struct task_struct {
 	struct list_head		ptrace_entry;
 
 	/* PID/PID hash table linkage. */
-	struct pid_link			pids[PIDTYPE_MAX];
+	struct pid			*thread_pid;
+	struct hlist_node		pid_links[PIDTYPE_MAX];
 	struct list_head		thread_group;
 	struct list_head		thread_node;
 
@@ -1209,27 +1210,7 @@ struct task_struct {
 
 static inline struct pid *task_pid(struct task_struct *task)
 {
-	return task->pids[PIDTYPE_PID].pid;
-}
-
-static inline struct pid *task_tgid(struct task_struct *task)
-{
-	return task->group_leader->pids[PIDTYPE_PID].pid;
-}
-
-/*
- * Without tasklist or RCU lock it is not safe to dereference
- * the result of task_pgrp/task_session even if task == current,
- * we can race with another thread doing sys_setsid/sys_setpgid.
- */
-static inline struct pid *task_pgrp(struct task_struct *task)
-{
-	return task->group_leader->pids[PIDTYPE_PGID].pid;
-}
-
-static inline struct pid *task_session(struct task_struct *task)
-{
-	return task->group_leader->pids[PIDTYPE_SID].pid;
+	return task->thread_pid;
 }
 
 /*
@@ -1278,7 +1259,7 @@ static inline pid_t task_tgid_nr(struct task_struct *tsk)
  */
 static inline int pid_alive(const struct task_struct *p)
 {
-	return p->pids[PIDTYPE_PID].pid != NULL;
+	return p->thread_pid != NULL;
 }
 
 static inline pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
@@ -1304,12 +1285,12 @@ static inline pid_t task_session_vnr(struct task_struct *tsk)
 
 static inline pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
 {
-	return __task_pid_nr_ns(tsk, __PIDTYPE_TGID, ns);
+	return __task_pid_nr_ns(tsk, PIDTYPE_TGID, ns);
 }
 
 static inline pid_t task_tgid_vnr(struct task_struct *tsk)
 {
-	return __task_pid_nr_ns(tsk, __PIDTYPE_TGID, NULL);
+	return __task_pid_nr_ns(tsk, PIDTYPE_TGID, NULL);
 }
 
 static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns)
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 113d1ad1ced7..4e9b77fb702d 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -69,6 +69,11 @@ struct thread_group_cputimer {
 	bool checking_timer;
 };
 
+struct multiprocess_signals {
+	sigset_t signal;
+	struct hlist_node node;
+};
+
 /*
  * NOTE! "signal_struct" does not have its own
  * locking, because a shared signal_struct always
@@ -90,6 +95,9 @@ struct signal_struct {
 	/* shared signal handling: */
 	struct sigpending	shared_pending;
 
+	/* For collecting multiprocess signals during fork */
+	struct hlist_head	multiprocess;
+
 	/* thread group exit support */
 	int			group_exit_code;
 	/* overloaded:
@@ -146,7 +154,8 @@ struct signal_struct {
 
 #endif
 
-	struct pid *leader_pid;
+	/* PID/PID hash table linkage. */
+	struct pid *pids[PIDTYPE_MAX];
 
 #ifdef CONFIG_NO_HZ_FULL
 	atomic_t tick_dep_mask;
@@ -329,7 +338,7 @@ extern int send_sig(int, struct task_struct *, int);
 extern int zap_other_threads(struct task_struct *p);
 extern struct sigqueue *sigqueue_alloc(void);
 extern void sigqueue_free(struct sigqueue *);
-extern int send_sigqueue(struct sigqueue *,  struct task_struct *, int group);
+extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
 extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
 
 static inline int restart_syscall(void)
@@ -371,6 +380,7 @@ static inline int signal_pending_state(long state, struct task_struct *p)
  */
 extern void recalc_sigpending_and_wake(struct task_struct *t);
 extern void recalc_sigpending(void);
+extern void calculate_sigpending(void);
 
 extern void signal_wake_up_state(struct task_struct *t, unsigned int state);
 
@@ -383,6 +393,8 @@ static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)
 	signal_wake_up_state(t, resume ? __TASK_TRACED : 0);
 }
 
+void task_join_group_stop(struct task_struct *task);
+
 #ifdef TIF_RESTORE_SIGMASK
 /*
  * Legacy restore_sigmask accessors.  These are inefficient on
@@ -556,6 +568,37 @@ extern bool current_is_single_threaded(void);
 typedef int (*proc_visitor)(struct task_struct *p, void *data);
 void walk_process_tree(struct task_struct *top, proc_visitor, void *);
 
+static inline
+struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
+{
+	struct pid *pid;
+	if (type == PIDTYPE_PID)
+		pid = task_pid(task);
+	else
+		pid = task->signal->pids[type];
+	return pid;
+}
+
+static inline struct pid *task_tgid(struct task_struct *task)
+{
+	return task->signal->pids[PIDTYPE_TGID];
+}
+
+/*
+ * Without tasklist or RCU lock it is not safe to dereference
+ * the result of task_pgrp/task_session even if task == current,
+ * we can race with another thread doing sys_setsid/sys_setpgid.
+ */
+static inline struct pid *task_pgrp(struct task_struct *task)
+{
+	return task->signal->pids[PIDTYPE_PGID];
+}
+
+static inline struct pid *task_session(struct task_struct *task)
+{
+	return task->signal->pids[PIDTYPE_SID];
+}
+
 static inline int get_nr_threads(struct task_struct *tsk)
 {
 	return tsk->signal->nr_threads;
@@ -574,7 +617,7 @@ static inline bool thread_group_leader(struct task_struct *p)
  */
 static inline bool has_group_leader_pid(struct task_struct *p)
 {
-	return task_pid(p) == p->signal->leader_pid;
+	return task_pid(p) == task_tgid(p);
 }
 
 static inline
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 3c5200137b24..fe125b0335f7 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -254,11 +254,13 @@ static inline int valid_signal(unsigned long sig)
 
 struct timespec;
 struct pt_regs;
+enum pid_type;
 
 extern int next_signal(struct sigpending *pending, sigset_t *mask);
 extern int do_send_sig_info(int sig, struct siginfo *info,
-				struct task_struct *p, bool group);
-extern int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p);
+				struct task_struct *p, enum pid_type type);
+extern int group_send_sig_info(int sig, struct siginfo *info,
+			       struct task_struct *p, enum pid_type type);
 extern int __group_send_sig_info(int, struct siginfo *, struct task_struct *);
 extern int sigprocmask(int, sigset_t *, sigset_t *);
 extern void set_current_blocked(sigset_t *);