The patch titled
migrate_timers: add comment, use spinlock_irq()
has been added to the -mm tree. Its filename is
migrate_timers-add-comment-use-spinlock_irq.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: migrate_timers: add comment, use spinlock_irq()
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Add the comment to explain why the double lock in migrate_timers()
can't deadlock.
Change the code to use spinlock_irq() instead of local_irq_disable()
+ spin_lock().
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Steven Rostedt <srostedt@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/hrtimer.c | 11 ++++++-----
kernel/timer.c | 11 ++++++-----
2 files changed, 12 insertions(+), 10 deletions(-)
diff -puN kernel/hrtimer.c~migrate_timers-add-comment-use-spinlock_irq kernel/hrtimer.c
--- a/kernel/hrtimer.c~migrate_timers-add-comment-use-spinlock_irq
+++ a/kernel/hrtimer.c
@@ -1612,9 +1612,11 @@ static void migrate_hrtimers(int cpu)
new_base = &get_cpu_var(hrtimer_bases);
tick_cancel_sched_timer(cpu);
-
- local_irq_disable();
- spin_lock(&new_base->lock);
+ /*
+ * The caller is globally serialized and nobody else
+ * takes two locks at once, deadlock is not possible.
+ */
+ spin_lock_irq(&new_base->lock);
spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
@@ -1623,8 +1625,7 @@ static void migrate_hrtimers(int cpu)
}
spin_unlock(&old_base->lock);
- spin_unlock(&new_base->lock);
- local_irq_enable();
+ spin_unlock_irq(&new_base->lock);
put_cpu_var(hrtimer_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */
diff -puN kernel/timer.c~migrate_timers-add-comment-use-spinlock_irq kernel/timer.c
--- a/kernel/timer.c~migrate_timers-add-comment-use-spinlock_irq
+++ a/kernel/timer.c
@@ -1435,9 +1435,11 @@ static void __cpuinit migrate_timers(int
BUG_ON(cpu_online(cpu));
old_base = per_cpu(tvec_bases, cpu);
new_base = get_cpu_var(tvec_bases);
-
- local_irq_disable();
- spin_lock(&new_base->lock);
+ /*
+ * The caller is globally serialized and nobody else
+ * takes two locks at once, deadlock is not possible.
+ */
+ spin_lock_irq(&new_base->lock);
spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
BUG_ON(old_base->running_timer);
@@ -1452,8 +1454,7 @@ static void __cpuinit migrate_timers(int
}
spin_unlock(&old_base->lock);
- spin_unlock(&new_base->lock);
- local_irq_enable();
+ spin_unlock_irq(&new_base->lock);
put_cpu_var(tvec_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
get_user_pages-fix-possible-page-leak-on-oom.patch
posix-timers-timer_delete-remove-the-bogus-it_process-=-null-check.patch
posix-timers-release_posix_timer-kill-the-bogus-put_task_struct-it_process.patch
signals-collect_signal-remove-the-unneeded-sigismember-check.patch
signals-collect_signal-simplify-the-still_pending-logic.patch
signals-change-collect_signal-to-return-void.patch
__exit_signal-dont-take-rcu-lock.patch
signals-dequeue_signal-dont-check-signal_group_exit-when-setting-signal_stop_dequeued.patch
signals-do_signal_stop-kill-the-signal_unkillable-check.patch
coredump-zap_threads-comments-use-while_each_thread.patch
signals-make-siginfo_t-si_utime-si_sstime-report-times-in-user_hz-not-hz.patch
kernel-signalc-change-vars-pid-and-tgid-types-to-pid_t.patch
include-asm-ptraceh-userspace-headers-cleanup.patch
ptrace-give-more-respect-to-sigkill.patch
ptrace-never-sleep-in-task_traced-if-sigkilled.patch
ptrace-kill-may_ptrace_stop.patch
introduce-pf_kthread-flag.patch
kill-pf_borrowed_mm-in-favour-of-pf_kthread.patch
coredump-zap_threads-must-skip-kernel-threads.patch
coredump-elf_core_dump-skip-kernel-threads.patch
pidns-remove-now-unused-kill_proc-function.patch
pidns-remove-now-unused-find_pid-function.patch
pidns-remove-find_task_by_pid-unused-for-a-long-time.patch
distinct-tgid-tid-i-o-statistics.patch
migrate_timers-add-comment-use-spinlock_irq.patch
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