1. 17 11月, 2009 6 次提交
  2. 16 11月, 2009 1 次提交
    • P
      perf_event: Optimize perf_output_lock() · 559fdc3c
      Peter Zijlstra 提交于
      The purpose of perf_output_{un,}lock() is to:
      
       1) avoid publishing incomplete data
          [ possible when publishing a head that is ahead of an entry
            that is still being written ]
      
       2) guarantee fwd progress
          [ a simple refcount on pending writers doesn't need to drop to
            0, making it so would end up implementing something like forced
            quiecent states of RCU ]
      
      To satisfy the above without undue complexity it serializes
      between CPUs, this means that a pending writer can only be the
      same cpu in a nested context, and since (under normal operation)
      a cpu always makes progress we're good -- if the head is only
      published when the bottom  most writer completes.
      
      Now we don't need to disable IRQs in order to serialize between
      CPUs, disabling preemption ought to be sufficient, esp since we
      already deal with nesting due to NMIs.
      
      This avoids potentially expensive (and needless) local IRQ
      disable/enable ops.
      Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      LKML-Reference: <1258373161.26714.254.camel@laptop>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      559fdc3c
  3. 15 11月, 2009 4 次提交
  4. 14 11月, 2009 1 次提交
  5. 13 11月, 2009 3 次提交
  6. 12 11月, 2009 25 次提交
新手
引导
客服 返回
顶部