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Subject[tip:timers/core] timer: Convert schedule_timeout() to use from_timer()
Commit-ID:  58e1177b4cd10b0d358faf7d7ebb3779f98bc3ea
Gitweb: https://git.kernel.org/tip/58e1177b4cd10b0d358faf7d7ebb3779f98bc3ea
Author: Kees Cook <keescook@chromium.org>
AuthorDate: Wed, 4 Oct 2017 16:26:55 -0700
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 5 Oct 2017 15:01:16 +0200

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 <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mips@linux-mips.org
Cc: Petr Mladek <pmladek@suse.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Kalle Valo <kvalo@qca.qualcomm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: linux1394-devel@lists.sourceforge.net
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: linux-s390@vger.kernel.org
Cc: linux-wireless@vger.kernel.org
Cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ursula Braun <ubraun@linux.vnet.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Harish Patil <harish.patil@cavium.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Manish Chopra <manish.chopra@cavium.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-pm@vger.kernel.org
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mark Gross <mark.gross@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linux-watchdog@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Michael Reed <mdr@sgi.com>
Cc: netdev@vger.kernel.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: https://lkml.kernel.org/r/1507159627-127660-2-git-send-email-keescook@chromium.org

---
include/linux/timer.h | 8 ++++++++
kernel/time/timer.c | 26 +++++++++++++++++++-------
2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/include/linux/timer.h b/include/linux/timer.h
index 6383c52..5ef5c9e 100644
--- a/include/linux/timer.h
+++ b/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)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index f2674a0..38613ce 100644
--- a/kernel/time/timer.c
+++ b/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;

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