Commit-ID: c55f5158f5606f8a62e694b7e009f59b92ac6258
Gitweb: http://git.kernel.org/tip/c55f5158f5606f8a62e694b7e009f59b92ac6258
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 23 Sep 2014 17:06:41 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 24 Sep 2014 14:47:05 +0200
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@xxxxxxxxxxxxx>
Reviewed-by: Kirill Tkhai <tkhai@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Davidlohr Bueso <davidlohr@xxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxxxx>
Cc: Qais Yousef <qais.yousef@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: oleg@xxxxxxxxxx
Cc: linux@xxxxxxxxxxxx
Cc: linux-ia64@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-mips@xxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20140923150641.GH3312@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/ia64/include/asm/processor.h | 1 -
arch/mips/include/asm/processor.h | 6 ------
kernel/sched/core.c | 6 ------
kernel/sched/sched.h | 30 ------------------------------
4 files changed, 43 deletions(-)
diff --git a/arch/ia64/include/asm/processor.h b/arch/ia64/include/asm/processor.h
index c736713..ce53c50 100644
--- a/arch/ia64/include/asm/processor.h
+++ b/arch/ia64/include/asm/processor.h
@@ -19,7 +19,6 @@
#include <asm/ptrace.h>
#include <asm/ustack.h>
-#define __ARCH_WANT_UNLOCKED_CTXSW
#define ARCH_HAS_PREFETCH_SWITCH_STACK
#define IA64_NUM_PHYS_STACK_REG 96
diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index 05f0843..f1df4cb 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -397,12 +397,6 @@ unsigned long get_wchan(struct task_struct *p);
#define ARCH_HAS_PREFETCHW
#define prefetchw(x) __builtin_prefetch((x), 1, 1)
-/*
- * See Documentation/scheduler/sched-arch.txt; prevents deadlock on SMP
- * systems.
- */
-#define __ARCH_WANT_UNLOCKED_CTXSW
-
#endif
#endif /* _ASM_PROCESSOR_H */
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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