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https://github.com/torvalds/linux
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e2336f6e51
task_preempt_count() is pointless if preemption counter is per-cpu, currently this is x86 only. It is only valid if the task is not running, and even in this case the only info it can provide is the state of PREEMPT_ACTIVE bit. Change its single caller to check p->on_rq instead, this should be the same if p->state != TASK_RUNNING, and kill this helper. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Kirill Tkhai <tkhai@yandex.ru> Cc: Alexander Graf <agraf@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-arch@vger.kernel.org Link: http://lkml.kernel.org/r/20141008183348.GC17495@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
110 lines
2.9 KiB
C
110 lines
2.9 KiB
C
#ifndef __ASM_PREEMPT_H
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#define __ASM_PREEMPT_H
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#include <asm/rmwcc.h>
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#include <asm/percpu.h>
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#include <linux/thread_info.h>
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DECLARE_PER_CPU(int, __preempt_count);
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/*
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* We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
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* that a decrement hitting 0 means we can and should reschedule.
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*/
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#define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
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/*
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* We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
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* that think a non-zero value indicates we cannot preempt.
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*/
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static __always_inline int preempt_count(void)
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{
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return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
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}
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static __always_inline void preempt_count_set(int pc)
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{
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raw_cpu_write_4(__preempt_count, pc);
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}
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/*
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* must be macros to avoid header recursion hell
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*/
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#define init_task_preempt_count(p) do { \
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task_thread_info(p)->saved_preempt_count = PREEMPT_DISABLED; \
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} while (0)
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#define init_idle_preempt_count(p, cpu) do { \
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task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \
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per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
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} while (0)
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/*
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* We fold the NEED_RESCHED bit into the preempt count such that
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* preempt_enable() can decrement and test for needing to reschedule with a
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* single instruction.
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*
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* We invert the actual bit, so that when the decrement hits 0 we know we both
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* need to resched (the bit is cleared) and can resched (no preempt count).
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*/
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static __always_inline void set_preempt_need_resched(void)
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{
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raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
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}
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static __always_inline void clear_preempt_need_resched(void)
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{
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raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
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}
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static __always_inline bool test_preempt_need_resched(void)
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{
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return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
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}
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/*
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* The various preempt_count add/sub methods
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*/
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static __always_inline void __preempt_count_add(int val)
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{
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raw_cpu_add_4(__preempt_count, val);
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}
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static __always_inline void __preempt_count_sub(int val)
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{
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raw_cpu_add_4(__preempt_count, -val);
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}
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/*
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* Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
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* a decrement which hits zero means we have no preempt_count and should
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* reschedule.
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*/
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static __always_inline bool __preempt_count_dec_and_test(void)
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{
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GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
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}
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/*
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* Returns true when we need to resched and can (barring IRQ state).
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*/
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static __always_inline bool should_resched(void)
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{
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return unlikely(!raw_cpu_read_4(__preempt_count));
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}
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#ifdef CONFIG_PREEMPT
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extern asmlinkage void ___preempt_schedule(void);
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# define __preempt_schedule() asm ("call ___preempt_schedule")
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extern asmlinkage void preempt_schedule(void);
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# ifdef CONFIG_CONTEXT_TRACKING
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extern asmlinkage void ___preempt_schedule_context(void);
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# define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
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extern asmlinkage void preempt_schedule_context(void);
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# endif
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#endif
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#endif /* __ASM_PREEMPT_H */
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