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Commit d87b7a33 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/core, sched/x86: Kill thread_info::saved_preempt_count 



With the introduction of the context switch preempt_count invariant,
and the demise of PREEMPT_ACTIVE, its pointless to save/restore the
per-cpu preemption count, it must always be 2.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent da7142e2

arch/x86/include/asm/preempt.h

+1 −4
Original line number Diff line number Diff line
@@ -30,12 +30,9 @@ static __always_inline void preempt_count_set(int pc) 
/*

 * must be macros to avoid header recursion hell

 */

#define init_task_preempt_count(p) do { \

	task_thread_info(p)->saved_preempt_count = FORK_PREEMPT_COUNT; \

} while (0)

#define init_task_preempt_count(p) do { } while (0)



#define init_idle_preempt_count(p, cpu) do { \

	task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \

	per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \

} while (0)

arch/x86/include/asm/thread_info.h

+0 −2
Original line number Diff line number Diff line
@@ -57,7 +57,6 @@ struct thread_info { 
	__u32			flags;		/* low level flags */

	__u32			status;		/* thread synchronous flags */

	__u32			cpu;		/* current CPU */

	int			saved_preempt_count;

	mm_segment_t		addr_limit;

	void __user		*sysenter_return;

	unsigned int		sig_on_uaccess_error:1;
@@ -69,7 +68,6 @@ struct thread_info { 
	.task		= &tsk,			\

	.flags		= 0,			\

	.cpu		= 0,			\

	.saved_preempt_count = INIT_PREEMPT_COUNT,	\

	.addr_limit	= KERNEL_DS,		\

}

arch/x86/kernel/process_32.c

+0 −8
Original line number Diff line number Diff line
@@ -279,14 +279,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
	if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))

		set_iopl_mask(next->iopl);



	/*

	 * If it were not for PREEMPT_ACTIVE we could guarantee that the

	 * preempt_count of all tasks was equal here and this would not be

	 * needed.

	 */

	task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);

	this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);



	/*

	 * Now maybe handle debug registers and/or IO bitmaps

	 */

arch/x86/kernel/process_64.c

+0 −8
Original line number Diff line number Diff line
@@ -401,14 +401,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
	 */

	this_cpu_write(current_task, next_p);



	/*

	 * If it were not for PREEMPT_ACTIVE we could guarantee that the

	 * preempt_count of all tasks was equal here and this would not be

	 * needed.

	 */

	task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);

	this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);



	/* Reload esp0 and ss1.  This changes current_thread_info(). */

	load_sp0(tss, next);