[patch v4 14/27] signal: Provide posixtimer_sigqueue_init()

[Thomas Gleixner <tglx@linutronix.de>]

From: Thomas Gleixner <tglx@linutronix.de>

To cure the SIG_IGN handling for posix interval timers, the preallocated
sigqueue needs to be embedded into struct k_itimer to prevent life time
races of all sorts.

Provide a new function to initialize the embedded sigqueue to prepare for
that.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

---
 include/linux/posix-timers.h |  2 ++
 kernel/signal.c              | 11 +++++++++++
 2 files changed, 13 insertions(+)
---
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 9740fd0c2933..200098d27cc0 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -12,6 +12,7 @@
 
 struct kernel_siginfo;
 struct task_struct;
+struct sigqueue;
 struct k_itimer;
 
 static inline clockid_t make_process_cpuclock(const unsigned int pid,
@@ -106,6 +107,7 @@ static inline void posix_cputimers_rt_watchdog(struct posix_cputimers *pct,
 }
 
 void posixtimer_rearm_itimer(struct task_struct *p);
+bool posixtimer_init_sigqueue(struct sigqueue *q);
 bool posixtimer_deliver_signal(struct kernel_siginfo *info);
 void posixtimer_free_timer(struct k_itimer *timer);
 
diff --git a/kernel/signal.c b/kernel/signal.c
index 87c349a2ddf7..a857f6628e77 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1905,6 +1905,17 @@ void flush_itimer_signals(void)
 	__flush_itimer_signals(&tsk->signal->shared_pending);
 }
 
+bool posixtimer_init_sigqueue(struct sigqueue *q)
+{
+	struct ucounts *ucounts = sig_get_ucounts(current, -1, 0);
+
+	if (!ucounts)
+		return false;
+	clear_siginfo(&q->info);
+	__sigqueue_init(q, ucounts, SIGQUEUE_PREALLOC);
+	return true;
+}
+
 struct sigqueue *sigqueue_alloc(void)
 {
 	return __sigqueue_alloc(-1, current, GFP_KERNEL, 0, SIGQUEUE_PREALLOC);