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authorPeter Zijlstra <peterz@infradead.org>2014-09-23 17:06:41 +0200
committerIngo Molnar <mingo@kernel.org>2014-09-24 14:47:05 +0200
commitc55f5158f5606f8a62e694b7e009f59b92ac6258 (patch)
treef51365aca7822ecf82a03c65c919b84274ff86a2 /kernel/sched
parent5bd96ab6fef66ec6b9f54134364e618fd0f8f2f3 (diff)
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sched, mips, ia64: Remove __ARCH_WANT_UNLOCKED_CTXSW
Kirill found that there's a subtle race in the __ARCH_WANT_UNLOCKED_CTXSW code, and instead of fixing it, remove the entire exception because neither arch that uses it seems to actually still require it. Boot tested on mips64el (qemu) only. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Kirill Tkhai <tkhai@yandex.ru> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Davidlohr Bueso <davidlohr@hp.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: James Hogan <james.hogan@imgtec.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Qais Yousef <qais.yousef@imgtec.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Tony Luck <tony.luck@intel.com> Cc: oleg@redhat.com Cc: linux@roeck-us.net Cc: linux-ia64@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-mips@linux-mips.org Link: http://lkml.kernel.org/r/20140923150641.GH3312@worktop.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/core.c6
-rw-r--r--kernel/sched/sched.h30
2 files changed, 0 insertions, 36 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d65566d..5b0eac9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2331,10 +2331,6 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev)
*/
post_schedule(rq);
-#ifdef __ARCH_WANT_UNLOCKED_CTXSW
- /* In this case, finish_task_switch does not reenable preemption */
- preempt_enable();
-#endif
if (current->set_child_tid)
put_user(task_pid_vnr(current), current->set_child_tid);
}
@@ -2377,9 +2373,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
* of the scheduler it's an obvious special-case), so we
* do an early lockdep release here:
*/
-#ifndef __ARCH_WANT_UNLOCKED_CTXSW
spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
-#endif
context_tracking_task_switch(prev, next);
/* Here we just switch the register state and the stack. */
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 16e1ca9..6130251 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -975,7 +975,6 @@ static inline int task_on_rq_migrating(struct task_struct *p)
# define finish_arch_post_lock_switch() do { } while (0)
#endif
-#ifndef __ARCH_WANT_UNLOCKED_CTXSW
static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
#ifdef CONFIG_SMP
@@ -1013,35 +1012,6 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
raw_spin_unlock_irq(&rq->lock);
}
-#else /* __ARCH_WANT_UNLOCKED_CTXSW */
-static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
-{
-#ifdef CONFIG_SMP
- /*
- * We can optimise this out completely for !SMP, because the
- * SMP rebalancing from interrupt is the only thing that cares
- * here.
- */
- next->on_cpu = 1;
-#endif
- raw_spin_unlock(&rq->lock);
-}
-
-static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
-{
-#ifdef CONFIG_SMP
- /*
- * After ->on_cpu is cleared, the task can be moved to a different CPU.
- * We must ensure this doesn't happen until the switch is completely
- * finished.
- */
- smp_wmb();
- prev->on_cpu = 0;
-#endif
- local_irq_enable();
-}
-#endif /* __ARCH_WANT_UNLOCKED_CTXSW */
-
/*
* wake flags
*/
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