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sched/idle, x86: Switch from TS_POLLING to TIF_POLLING_NRFLAG

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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: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-04-11 09:59:05 +02:00 committed by Ingo Molnar
parent 0407542533
commit f80c5b39b8
2 changed files with 2 additions and 13 deletions
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4
arch/x86/include/asm/thread_info.h
View file

@ -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__

11
arch/x86/kernel/apm_32.c
View file

@ -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;