1. 05 6月, 2014 7 次提交
  2. 22 5月, 2014 12 次提交
  3. 08 5月, 2014 1 次提交
    • P
      sched/idle: Avoid spurious wakeup IPIs · fd99f91a
      Peter Zijlstra 提交于
      Because mwait_idle_with_hints() gets called from !idle context it must
      call current_clr_polling(). This however means that resched_task() is
      very likely to send an IPI even when we were polling:
      
        CPU0					CPU1
      
        if (current_set_polling_and_test())
          goto out;
      
        __monitor(&ti->flags);
        if (!need_resched())
          __mwait(eax, ecx);
      					set_tsk_need_resched(p);
      					smp_mb();
      out:
        current_clr_polling();
      					if (!tsk_is_polling(p))
      					  smp_send_reschedule(cpu);
      
      So while it is correct (extra IPIs aren't a problem, whereas a missed
      IPI would be) it is a performance problem (for some).
      
      Avoid this issue by using fetch_or() to atomically set NEED_RESCHED
      and test if POLLING_NRFLAG is set.
      
      Since a CPU stuck in mwait is unlikely to modify the flags word,
      contention on the cmpxchg is unlikely and thus we should mostly
      succeed in a single go.
      Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
      Acked-by: NNicolas Pitre <nico@linaro.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Link: http://lkml.kernel.org/n/tip-kf5suce6njh5xf5d3od13rr0@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>
      fd99f91a
  4. 07 5月, 2014 7 次提交
  5. 06 5月, 2014 1 次提交
  6. 24 4月, 2014 1 次提交
  7. 08 4月, 2014 2 次提交
  8. 20 3月, 2014 1 次提交
  9. 13 3月, 2014 1 次提交
  10. 12 3月, 2014 1 次提交
    • S
      sched: Fix broken setscheduler() · 383afd09
      Steven Rostedt 提交于
      I decided to run my tests on linux-next, and my wakeup_rt tracer was
      broken. After running a bisect, I found that the problem commit was:
      
         linux-next commit c365c292
         "sched: Consider pi boosting in setscheduler()"
      
      And the reason the wake_rt tracer test was failing, was because it had
      no RT task to trace. I first noticed this when running with
      sched_switch event and saw that my RT task still had normal SCHED_OTHER
      priority. Looking at the problem commit, I found:
      
       -       p->normal_prio = normal_prio(p);
       -       p->prio = rt_mutex_getprio(p);
      
      With no
      
       +       p->normal_prio = normal_prio(p);
       +       p->prio = rt_mutex_getprio(p);
      
      Reading what the commit is suppose to do, I realize that the p->prio
      can't be set if the task is boosted with a higher prio, but the
      p->normal_prio still needs to be set regardless, otherwise, when the
      task is deboosted, it wont get the new priority.
      
      The p->prio has to be set before "check_class_changed()" is called,
      otherwise the class wont be changed.
      
      Also added fix to newprio to include a check for deadline policy that
      was missing. This change was suggested by Juri Lelli.
      Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      Cc: SebastianAndrzej Siewior <bigeasy@linutronix.de>
      Cc: Juri Lelli <juri.lelli@gmail.com>
      Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/20140306120438.638bfe94@gandalf.local.homeSigned-off-by: NIngo Molnar <mingo@kernel.org>
      383afd09
  11. 11 3月, 2014 2 次提交
  12. 27 2月, 2014 1 次提交
  13. 25 2月, 2014 2 次提交
    • F
      smp: Rename __smp_call_function_single() to smp_call_function_single_async() · c46fff2a
      Frederic Weisbecker 提交于
      The name __smp_call_function_single() doesn't tell much about the
      properties of this function, especially when compared to
      smp_call_function_single().
      
      The comments above the implementation are also misleading. The main
      point of this function is actually not to be able to embed the csd
      in an object. This is actually a requirement that result from the
      purpose of this function which is to raise an IPI asynchronously.
      
      As such it can be called with interrupts disabled. And this feature
      comes at the cost of the caller who then needs to serialize the
      IPIs on this csd.
      
      Lets rename the function and enhance the comments so that they reflect
      these properties.
      Suggested-by: NChristoph Hellwig <hch@infradead.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@fb.com>
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      Signed-off-by: NJens Axboe <axboe@fb.com>
      c46fff2a
    • F
      smp: Remove wait argument from __smp_call_function_single() · fce8ad15
      Frederic Weisbecker 提交于
      The main point of calling __smp_call_function_single() is to send
      an IPI in a pure asynchronous way. By embedding a csd in an object,
      a caller can send the IPI without waiting for a previous one to complete
      as is required by smp_call_function_single() for example. As such,
      sending this kind of IPI can be safe even when irqs are disabled.
      
      This flexibility comes at the expense of the caller who then needs to
      synchronize the csd lifecycle by himself and make sure that IPIs on a
      single csd are serialized.
      
      This is how __smp_call_function_single() works when wait = 0 and this
      usecase is relevant.
      
      Now there don't seem to be any usecase with wait = 1 that can't be
      covered by smp_call_function_single() instead, which is safer. Lets look
      at the two possible scenario:
      
      1) The user calls __smp_call_function_single(wait = 1) on a csd embedded
         in an object. It looks like a nice and convenient pattern at the first
         sight because we can then retrieve the object from the IPI handler easily.
      
         But actually it is a waste of memory space in the object since the csd
         can be allocated from the stack by smp_call_function_single(wait = 1)
         and the object can be passed an the IPI argument.
      
         Besides that, embedding the csd in an object is more error prone
         because the caller must take care of the serialization of the IPIs
         for this csd.
      
      2) The user calls __smp_call_function_single(wait = 1) on a csd that
         is allocated on the stack. It's ok but smp_call_function_single()
         can do it as well and it already takes care of the allocation on the
         stack. Again it's more simple and less error prone.
      
      Therefore, using the underscore prepend API version with wait = 1
      is a bad pattern and a sign that the caller can do safer and more
      simple.
      
      There was a single user of that which has just been converted.
      So lets remove this option to discourage further users.
      
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Christoph Hellwig <hch@infradead.org>
      Cc: Ingo Molnar <mingo@kernel.org>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@fb.com>
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      Signed-off-by: NJens Axboe <axboe@fb.com>
      fce8ad15
  14. 23 2月, 2014 1 次提交