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  1. 17 Apr, 2008 2 commits
  2. 10 Apr, 2008 1 commit
  3. 29 Feb, 2008 1 commit
  4. 08 Feb, 2008 2 commits
  5. 04 Feb, 2008 1 commit
  6. 30 Jan, 2008 20 commits
  7. 14 Jan, 2008 1 commit
    • Steven Rostedt's avatar
      Kick CPUS that might be sleeping in cpus_idle_wait · 40d6a146
      Steven Rostedt authored
      Sometimes cpu_idle_wait gets stuck because it might miss CPUS that are
      already in idle, have no tasks waiting to run and have no interrupts going
      to them.  This is common on bootup when switching cpu idle governors.
      
      This patch gives those CPUS that don't check in an IPI kick.
      
       Background:
       -----------
      I notice this while developing the mcount patches, that every once in a
      while the system would hang. Looking deeper, the hang was always at boot
      up when registering init_menu of the cpu_idle menu governor. Talking
      with Thomas Gliexner, we discovered that one of the CPUS had no timer
      events scheduled for it and it was in idle (running with NO_HZ). So the
      CPU would not set the cpu_idle_state bit.
      
      Hitting sysrq-t a few times would eventually route the interrupt to the
      stuck CPU and the system would continue.
      
      Note, I would have used the PDA isidle but that is set after the
      cpu_idle_state bit is cleared, and would leave a window open where we
      may miss being kicked.
      
      hmm, looking closer at this, we still have a small race window between
      clearing the cpu_idle_state and disabling interrupts (hence the RFC).
      
          CPU0:                          CPU 1:
        ---------                       ---------
       cpu_idle_wait():                 cpu_idle():
            |                           __cpu_cpu_var(is_idle) = 1;
            |                           if (__get_cpu_var(cpu_idle_state)) /* == 0 */
       per_cpu(cpu_idle_state, 1) = 1;         |
       if (per_cpu(is_idle, 1)) /* == 1 */     |
       smp_call_function(1)                    |
            |                             receives ipi and runs do_nothing.
       wait on map == empty               idle();
         /* waits forever */
      
      So really we need interrupts off for most of this then. One might think
      that we could simply clear the cpu_idle_state from do_nothing, but I'm
      assuming that cpu_idle governors can be removed, and this might cause a
      race that a governor might be used after the module was removed.
      
      Venki said:
      
        I think your RFC patch is the right solution here.  As I see it, there is
        no race with your RFC patch.  As long as you call a dummy smp_call_function
        on all CPUs, we should be OK.  We can get rid of cpu_idle_state and the
        current wait forever logic altogether with dummy smp_call_function.  And so
        there wont be any wait forever scenario.
      
        The whole point of cpu_idle_wait() is to make all CPUs come out of idle
        loop atleast once.  The caller will use cpu_idle_wait something like this.
      
        // Want to change idle handler
      
        - Switch global idle handler to always present default_idle
      
        - call cpu_idle_wait so that all cpus come out of idle for an instant
          and stop using old idle pointer and start using default idle
      
        - Change the idle handler to a new handler
      
        - optional cpu_idle_wait if you want all cpus to start using the new
          handler immediately.
      
      Maybe the below 1s patch is safe bet for .24.  But for .25, I would say we
      just replace all complicated logic by simple dummy smp_call_function and
      remove cpu_idle_state altogether.
      Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
      Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
      Acked-by: default avatarIngo Molnar <mingo@elte.hu>
      Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Andi Kleen <ak@suse.de>
      Cc: Len Brown <lenb@kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      40d6a146
  8. 19 Dec, 2007 1 commit
  9. 19 Oct, 2007 2 commits
  10. 13 Oct, 2007 1 commit
    • Dave Jones's avatar
      Delete filenames in comments. · 835c34a1
      Dave Jones authored
      Since the x86 merge, lots of files that referenced their own filenames
      are no longer correct.  Rather than keep them up to date, just delete
      them, as they add no real value.
      
      Additionally:
      - fix up comment formatting in scx200_32.c
      - Remove a credit from myself in setup_64.c from a time when we had no SCM
      - remove longwinded history from tsc_32.c which can be figured out from
        git.
      Signed-off-by: default avatarDave Jones <davej@redhat.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      835c34a1
  11. 11 Oct, 2007 2 commits
  12. 22 Jul, 2007 1 commit
  13. 16 Jul, 2007 1 commit
  14. 12 May, 2007 1 commit
  15. 08 May, 2007 1 commit
  16. 02 May, 2007 2 commits
    • Jeremy Fitzhardinge's avatar
      [PATCH] i386: Convert PDA into the percpu section · 7c3576d2
      Jeremy Fitzhardinge authored
      Currently x86 (similar to x84-64) has a special per-cpu structure
      called "i386_pda" which can be easily and efficiently referenced via
      the %fs register.  An ELF section is more flexible than a structure,
      allowing any piece of code to use this area.  Indeed, such a section
      already exists: the per-cpu area.
      
      So this patch:
      (1) Removes the PDA and uses per-cpu variables for each current member.
      (2) Replaces the __KERNEL_PDA segment with __KERNEL_PERCPU.
      (3) Creates a per-cpu mirror of __per_cpu_offset called this_cpu_off, which
          can be used to calculate addresses for this CPU's variables.
      (4) Simplifies startup, because %fs doesn't need to be loaded with a
          special segment at early boot; it can be deferred until the first
          percpu area is allocated (or never for UP).
      
      The result is less code and one less x86-specific concept.
      Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
      Signed-off-by: default avatarAndi Kleen <ak@suse.de>
      Cc: Andi Kleen <ak@suse.de>
      7c3576d2
    • Rusty Russell's avatar
      [PATCH] i386: i386 separate hardware-defined TSS from Linux additions · a75c54f9
      Rusty Russell authored
      On Thu, 2007-03-29 at 13:16 +0200, Andi Kleen wrote:
      > Please clean it up properly with two structs.
      
      Not sure about this, now I've done it.  Running it here.
      
      If you like it, I can do x86-64 as well.
      
      ==
      lguest defines its own TSS struct because the "struct tss_struct"
      contains linux-specific additions.  Andi asked me to split the struct
      in processor.h.
      
      Unfortunately it makes usage a little awkward.
      Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      Signed-off-by: default avatarAndi Kleen <ak@suse.de>
      a75c54f9