timer: Convert schedule_timeout() to use from_timer()

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new from_timer() helper and passing
the timer pointer explicitly. Since this special timer is on the stack, it
needs to have a wrapper structure to carry state once .data is eliminated.

Signed-off-by: Kees Cook <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: Petr Mladek <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Sebastian Reichel <[email protected]>
Cc: Kalle Valo <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: [email protected]
Cc: Chris Metcalf <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Wim Van Sebroeck <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Ursula Braun <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Viresh Kumar <[email protected]>
Cc: Harish Patil <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: Manish Chopra <[email protected]>
Cc: Len Brown <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: [email protected]
Cc: Heiko Carstens <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Julian Wiedmann <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Mark Gross <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: "Martin K. Petersen" <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Stephen Boyd <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Stefan Richter <[email protected]>
Cc: Michael Reed <[email protected]>
Cc: [email protected]
Cc: Martin Schwidefsky <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: [email protected]
Cc: Sudip Mukherjee <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

include/linux/timer.h

@@ -179,6 +179,14 @@ static inline void timer_setup(struct timer_list *timer,
 		      (TIMER_DATA_TYPE)timer, flags);
 }
 
+static inline void timer_setup_on_stack(struct timer_list *timer,
+			       void (*callback)(struct timer_list *),
+			       unsigned int flags)
+{
+	__setup_timer_on_stack(timer, (TIMER_FUNC_TYPE)callback,
+			       (TIMER_DATA_TYPE)timer, flags);
+}
+
 #define from_timer(var, callback_timer, timer_fieldname) \
 	container_of(callback_timer, typeof(*var), timer_fieldname)
 

kernel/time/timer.c

@@ -1668,9 +1668,20 @@ void run_local_timers(void)
 	raise_softirq(TIMER_SOFTIRQ);
 }
 
-static void process_timeout(unsigned long __data)
+/*
+ * Since schedule_timeout()'s timer is defined on the stack, it must store
+ * the target task on the stack as well.
+ */
+struct process_timer {
+	struct timer_list timer;
+	struct task_struct *task;
+};
+
+static void process_timeout(struct timer_list *t)
 {
-	wake_up_process((struct task_struct *)__data);
+	struct process_timer *timeout = from_timer(timeout, t, timer);
+
+	wake_up_process(timeout->task);
 }
 
 /**
@@ -1704,7 +1715,7 @@ static void process_timeout(unsigned long __data)
  */
 signed long __sched schedule_timeout(signed long timeout)
 {
-	struct timer_list timer;
+	struct process_timer timer;
 	unsigned long expire;
 
 	switch (timeout)
@@ -1738,13 +1749,14 @@ signed long __sched schedule_timeout(signed long timeout)
 
 	expire = timeout + jiffies;
 
-	setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
-	__mod_timer(&timer, expire, false);
+	timer.task = current;
+	timer_setup_on_stack(&timer.timer, process_timeout, 0);
+	__mod_timer(&timer.timer, expire, false);
 	schedule();
-	del_singleshot_timer_sync(&timer);
+	del_singleshot_timer_sync(&timer.timer);
 
 	/* Remove the timer from the object tracker */
-	destroy_timer_on_stack(&timer);
+	destroy_timer_on_stack(&timer.timer);
 
 	timeout = expire - jiffies;