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: 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>

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 47e5de2..8540538 100644 (file)
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -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__

diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c
index 3ab0343..f3a1f04 100644 (file)
--- a/arch/x86/kernel/apm_32.c
+++ b/arch/x86/kernel/apm_32.c
@@ -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;