1. 02 12月, 2008 1 次提交
  2. 29 11月, 2008 2 次提交
  3. 27 11月, 2008 1 次提交
    • S
      sched: prevent divide by zero error in cpu_avg_load_per_task · 4cd42620
      Steven Rostedt 提交于
      Impact: fix divide by zero crash in scheduler rebalance irq
      
      While testing the branch profiler, I hit this crash:
      
      divide error: 0000 [#1] PREEMPT SMP
      [...]
      RIP: 0010:[<ffffffff8024a008>]  [<ffffffff8024a008>] cpu_avg_load_per_task+0x50/0x7f
      [...]
      Call Trace:
       <IRQ> <0> [<ffffffff8024fd43>] find_busiest_group+0x3e5/0xcaa
       [<ffffffff8025da75>] rebalance_domains+0x2da/0xa21
       [<ffffffff80478769>] ? find_next_bit+0x1b2/0x1e6
       [<ffffffff8025e2ce>] run_rebalance_domains+0x112/0x19f
       [<ffffffff8026d7c2>] __do_softirq+0xa8/0x232
       [<ffffffff8020ea7c>] call_softirq+0x1c/0x3e
       [<ffffffff8021047a>] do_softirq+0x94/0x1cd
       [<ffffffff8026d5eb>] irq_exit+0x6b/0x10e
       [<ffffffff8022e6ec>] smp_apic_timer_interrupt+0xd3/0xff
       [<ffffffff8020e4b3>] apic_timer_interrupt+0x13/0x20
      
      The code for cpu_avg_load_per_task has:
      
      	if (rq->nr_running)
      		rq->avg_load_per_task = rq->load.weight / rq->nr_running;
      
      The runqueue lock is not held here, and there is nothing that prevents
      the rq->nr_running from going to zero after it passes the if condition.
      
      The branch profiler simply made the race window bigger.
      
      This patch saves off the rq->nr_running to a local variable and uses that
      for both the condition and the division.
      Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
      Peter Zijlstra <peterz@infradead.org>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      4cd42620
  4. 25 11月, 2008 1 次提交
  5. 21 11月, 2008 26 次提交
  6. 20 11月, 2008 9 次提交