1. 08 8月, 2015 6 次提交
  2. 21 7月, 2015 3 次提交
  3. 16 7月, 2015 3 次提交
  4. 13 7月, 2015 11 次提交
  5. 08 7月, 2015 1 次提交
  6. 07 7月, 2015 1 次提交
    • S
      powerpc/powernv: Fix race in updating core_idle_state · b32aadc1
      Shreyas B. Prabhu 提交于
      core_idle_state is maintained for each core. It uses 0-7 bits to track
      whether a thread in the core has entered fastsleep or winkle. 8th bit is
      used as a lock bit.
      The lock bit is set in these 2 scenarios-
       - The thread is first in subcore to wakeup from sleep/winkle.
       - If its the last thread in the core about to enter sleep/winkle
      
      While the lock bit is set, if any other thread in the core wakes up, it
      loops until the lock bit is cleared before proceeding in the wakeup
      path. This helps prevent race conditions w.r.t fastsleep workaround and
      prevents threads from switching to process context before core/subcore
      resources are restored.
      
      But, in the path to sleep/winkle entry, we currently don't check for
      lock-bit. This exposes us to following race when running with subcore
      on-
      
      First thread in the subcorea		Another thread in the same
      waking up		   		core entering sleep/winkle
      
      lwarx   r15,0,r14
      ori     r15,r15,PNV_CORE_IDLE_LOCK_BIT
      stwcx.  r15,0,r14
      [Code to restore subcore state]
      
      						lwarx   r15,0,r14
      						[clear thread bit]
      						stwcx.  r15,0,r14
      
      andi.   r15,r15,PNV_CORE_IDLE_THREAD_BITS
      stw     r15,0(r14)
      
      Here, after the thread entering sleep clears its thread bit in
      core_idle_state, the value is overwritten by the thread waking up.
      In such cases when the core enters fastsleep, code mistakes an idle
      thread as running. Because of this, the first thread waking up from
      fastsleep which is supposed to resync timebase skips it. So we can
      end up having a core with stale timebase value.
      
      This patch fixes the above race by looping on the lock bit even while
      entering the idle states.
      Signed-off-by: NShreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
      Fixes: 7b54e9f213f76 'powernv/powerpc: Add winkle support for offline cpus'
      Cc: stable@vger.kernel.org # 3.19+
      Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
      b32aadc1
  7. 06 7月, 2015 5 次提交
  8. 26 6月, 2015 1 次提交
  9. 25 6月, 2015 8 次提交
  10. 24 6月, 2015 1 次提交