Commit f80c5b39 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/idle, x86: Switch from TS_POLLING to TIF_POLLING_NRFLAG 



Standardize the idle polling indicator to TIF_POLLING_NRFLAG such that
both TIF_NEED_RESCHED and TIF_POLLING_NRFLAG are in the same word.
This will allow us, using fetch_or(), to both set NEED_RESCHED and
check for POLLING_NRFLAG in a single operation and avoid pointless
wakeups.

Changing from the non-atomic thread_info::status flags to the atomic
thread_info::flags shouldn't be a big issue since most polling state
changes were followed/preceded by a full memory barrier anyway.

Also, fix up the apm_32 idle function, clearly that was forgotten in
the last conversion. The default idle state is !POLLING so just kill
the lot.

Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Link: http://lkml.kernel.org/n/tip-7yksmqtlv4nfowmlqr1rifoi@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 04075425

arch/x86/include/asm/thread_info.h

+2 −2
Original line number Diff line number Diff line
@@ -83,6 +83,7 @@ struct thread_info { 
#define TIF_FORK		18	/* ret_from_fork */

#define TIF_NOHZ		19	/* in adaptive nohz mode */

#define TIF_MEMDIE		20	/* is terminating due to OOM killer */

#define TIF_POLLING_NRFLAG	21	/* idle is polling for TIF_NEED_RESCHED */

#define TIF_IO_BITMAP		22	/* uses I/O bitmap */

#define TIF_FORCED_TF		24	/* true if TF in eflags artificially */

#define TIF_BLOCKSTEP		25	/* set when we want DEBUGCTLMSR_BTF */
@@ -106,6 +107,7 @@ struct thread_info { 
#define _TIF_IA32		(1 << TIF_IA32)

#define _TIF_FORK		(1 << TIF_FORK)

#define _TIF_NOHZ		(1 << TIF_NOHZ)

#define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)

#define _TIF_IO_BITMAP		(1 << TIF_IO_BITMAP)

#define _TIF_FORCED_TF		(1 << TIF_FORCED_TF)

#define _TIF_BLOCKSTEP		(1 << TIF_BLOCKSTEP)
@@ -191,8 +193,6 @@ static inline struct thread_info *current_thread_info(void) 
 * have to worry about atomic accesses.

 */

#define TS_COMPAT		0x0002	/* 32bit syscall active (64BIT)*/

#define TS_POLLING		0x0004	/* idle task polling need_resched,

					   skip sending interrupt */

#define TS_RESTORE_SIGMASK	0x0008	/* restore signal mask in do_signal() */



#ifndef __ASSEMBLY__

arch/x86/kernel/apm_32.c

+0 −11
Original line number Diff line number Diff line
@@ -844,21 +844,10 @@ static int apm_do_idle(void) 
	int polling;

	int err = 0;



	polling = !!(current_thread_info()->status & TS_POLLING);

	if (polling) {

		current_thread_info()->status &= ~TS_POLLING;

		/*

		 * TS_POLLING-cleared state must be visible before we

		 * test NEED_RESCHED:

		 */

		smp_mb();

	}

	if (!need_resched()) {

		idled = 1;

		ret = apm_bios_call_simple(APM_FUNC_IDLE, 0, 0, &eax, &err);

	}

	if (polling)

		current_thread_info()->status |= TS_POLLING;



	if (!idled)

		return 0;

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