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  1. 20 Nov, 2008 1 commit
    • Steven Rostedt's avatar
      powerpc: ftrace, do not latency trace idle · 6d07bb47
      Steven Rostedt authored 
      
Impact: fix for irq off latency tracer

When idle is called, interrupts are disabled, but the idle function
will still wake up on an interrupt. The problem is that the interrupt
disabled latency tracer will take this call to idle as a latency.

This patch disables the latency tracing when going into idle.
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
      6d07bb47
  3. 30 Sep, 2008 1 commit
  5. 18 Jul, 2008 1 commit
    • Thomas Gleixner's avatar
      nohz: prevent tick stop outside of the idle loop · b8f8c3cf
      Thomas Gleixner authored 
      
Jack Ren and Eric Miao tracked down the following long standing
problem in the NOHZ code:

	scheduler switch to idle task
	enable interrupts

Window starts here

	----> interrupt happens (does not set NEED_RESCHED)
	      	irq_exit() stops the tick

	----> interrupt happens (does set NEED_RESCHED)

	return from schedule()
	
	cpu_idle(): preempt_disable();

Window ends here

The interrupts can happen at any point inside the race window. The
first interrupt stops the tick, the second one causes the scheduler to
rerun and switch away from idle again and we end up with the tick
disabled.

The fact that it needs two interrupts where the first one does not set
NEED_RESCHED and the second one does made the bug obscure and extremly
hard to reproduce and analyse. Kudos to Jack and Eric.

Solution: Limit the NOHZ functionality to the idle loop to make sure
that we can not run into such a situation ever again.

cpu_idle()
{
	preempt_disable();

	while(1) {
		 tick_nohz_stop_sched_tick(1); <- tell NOHZ code that we
		 			          are in the idle loop

		 while (!need_resched())
		       halt();

		 tick_nohz_restart_sched_tick(); <- disables NOHZ mode
		 preempt_enable_no_resched();
		 schedule();
		 preempt_disable();
	}
}

In hindsight we should have done this forever, but ... 

/me grabs a large brown paperbag.

Debugged-by: Jack Ren <jack.ren@marvell.com>, 
Debugged-by: default avatareric miao <eric.y.miao@gmail.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      b8f8c3cf
  7. 08 Nov, 2007 1 commit
  9. 03 Oct, 2007 1 commit
  11. 07 May, 2007 1 commit
  13. 14 Feb, 2007 2 commits
  15. 25 Oct, 2006 1 commit
  17. 30 Jun, 2006 1 commit
  19. 13 Apr, 2006 1 commit
  21. 27 Mar, 2006 1 commit
    • Paul Mackerras's avatar
      powerpc: Unify the 32 and 64 bit idle loops · a0652fc9
      Paul Mackerras authored 
      
This unifies the 32-bit (ARCH=ppc and ARCH=powerpc) and 64-bit idle
loops.  It brings over the concept of having a ppc_md.power_save
function from 32-bit to ARCH=powerpc, which lets us get rid of
native_idle().  With this we will also be able to simplify the idle
handling for pSeries and cell.
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
      a0652fc9
  23. 18 Nov, 2005 1 commit
  25. 10 Nov, 2005 1 commit
  27. 09 Nov, 2005 2 commits
    • Nick Piggin's avatar
      [PATCH] sched: resched and cpu_idle rework · 64c7c8f8
      Nick Piggin authored 
      
Make some changes to the NEED_RESCHED and POLLING_NRFLAG to reduce
confusion, and make their semantics rigid.  Improves efficiency of
resched_task and some cpu_idle routines.

* In resched_task:
- TIF_NEED_RESCHED is only cleared with the task's runqueue lock held,
  and as we hold it during resched_task, then there is no need for an
  atomic test and set there. The only other time this should be set is
  when the task's quantum expires, in the timer interrupt - this is
  protected against because the rq lock is irq-safe.

- If TIF_NEED_RESCHED is set, then we don't need to do anything. It
  won't get unset until the task get's schedule()d off.

- If we are running on the same CPU as the task we resched, then set
  TIF_NEED_RESCHED and no further action is required.

- If we are running on another CPU, and TIF_POLLING_NRFLAG is *not* set
  after TIF_NEED_RESCHED has been set, then we need to send an IPI.

Using these rules, we are able to remove the test and set operation in
resched_task, and make clear the previously vague semantics of
POLLING_NRFLAG.

* In idle routines:
- Enter cpu_idle with preempt disabled. When the need_resched() condition
  becomes true, explicitly call schedule(). This makes things a bit clearer
  (IMO), but haven't updated all architectures yet.

- Many do a test and clear of TIF_NEED_RESCHED for some reason. According
  to the resched_task rules, this isn't needed (and actually breaks the
  assumption that TIF_NEED_RESCHED is only cleared with the runqueue lock
  held). So remove that. Generally one less locked memory op when switching
  to the idle thread.

- Many idle routines clear TIF_POLLING_NRFLAG, and only set it in the inner
  most polling idle loops. The above resched_task semantics allow it to be
  set until before the last time need_resched() is checked before going into
  a halt requiring interrupt wakeup.

  Many idle routines simply never enter such a halt, and so POLLING_NRFLAG
  can be always left set, completely eliminating resched IPIs when rescheduling
  the idle task.

  POLLING_NRFLAG width can be increased, to reduce the chance of resched IPIs.
Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Con Kolivas <kernel@kolivas.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      64c7c8f8
    • Nick Piggin's avatar
      [PATCH] sched: disable preempt in idle tasks · 5bfb5d69
      Nick Piggin authored 
      
Run idle threads with preempt disabled.

Also corrected a bugs in arm26's cpu_idle (make it actually call schedule()).
How did it ever work before?

Might fix the CPU hotplugging hang which Nigel Cunningham noted.

We think the bug hits if the idle thread is preempted after checking
need_resched() and before going to sleep, then the CPU offlined.

After calling stop_machine_run, the CPU eventually returns from preemption and
into the idle thread and goes to sleep.  The CPU will continue executing
previous idle and have no chance to call play_dead.

By disabling preemption until we are ready to explicitly schedule, this bug is
fixed and the idle threads generally become more robust.

From: alexs <ashepard@u.washington.edu>

  PPC build fix

From: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>

  MIPS build fix
Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarYoichi Yuasa <yuasa@hh.iij4u.or.jp>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: Linus To...
      5bfb5d69
  29. 07 Nov, 2005 1 commit
    • Paul Mackerras's avatar
      powerpc: Various UP build fixes · 2249ca9d
      Paul Mackerras authored 
      
Mostly this involves adding #include <asm/smp.h>, since that defines
things like boot_cpuid[_phys] and [gs]et_hard_smp_processor_id, which
are SMP-related but still needed on UP.  This incorporates fixes
posted by Olof Johansson and Heikki Lindholm.
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
      2249ca9d
  31. 19 Oct, 2005 1 commit
    • Paul Mackerras's avatar
      powerpc: Merge machdep.h · 143a1dec
      Paul Mackerras authored 
      
A few things change for consistency between ppc32 and ppc64:
idle functions return void; *_get_boot_time functions return
unsigned long (i.e. time_t) rather than filling in a struct rtc_time
(since that's useful to the callers and easier for pmac to
generate); *_get_rtc_time and *_set_rtc_time functions take
a struct rtc_time; irq_canonicalize is gone; nvram_sync returns
void.
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
      143a1dec
  33. 08 Jul, 2005 5 commits
  35. 30 Jun, 2005 3 commits
  37. 22 Jun, 2005 2 commits
    • Stephen Rothwell's avatar
      [PATCH] ppc64 iSeries: cleanup ItLpQueue.h · c92877e0
      Stephen Rothwell authored 
      
Just white space cleaups and move process_iSeries_events into its only caller.
Signed-off-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      c92877e0
    • Ingo Molnar's avatar
      [PATCH] smp_processor_id() cleanup · 39c715b7
      Ingo Molnar authored 
      
This patch implements a number of smp_processor_id() cleanup ideas that
Arjan van de Ven and I came up with.

The previous __smp_processor_id/_smp_processor_id/smp_processor_id API
spaghetti was hard to follow both on the implementational and on the
usage side.

Some of the complexity arose from picking wrong names, some of the
complexity comes from the fact that not all architectures defined
__smp_processor_id.

In the new code, there are two externally visible symbols:

 - smp_processor_id(): debug variant.

 - raw_smp_processor_id(): nondebug variant. Replaces all existing
   uses of _smp_processor_id() and __smp_processor_id(). Defined
   by every SMP architecture in include/asm-*/smp.h.

There is one new internal symbol, dependent on DEBUG_PREEMPT:

 - debug_smp_processor_id(): internal debug variant, mapped to
                             smp_processor_id().

Also, i moved debug_smp_processor_id() from lib/kernel_lock.c into a new
lib/smp_processor_id.c file.  All related comments got updated and/or
clarified.

I have build/boot tested the following 8 .config combinations on x86:

 {SMP,UP} x {PREEMPT,!PREEMPT} x {DEBUG_PREEMPT,!DEBUG_PREEMPT}

I have also build/boot tested x64 on UP/PREEMPT/DEBUG_PREEMPT.  (Other
architectures are untested, but should work just fine.)
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarArjan van de Ven <arjan@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      39c715b7
  39. 02 Jun, 2005 1 commit
  41. 16 Apr, 2005 1 commit
    • Linus Torvalds's avatar
      Linux-2.6.12-rc2 · 1da177e4
      Linus Torvalds authored 
      Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
      1da177e4