1. 16 Mar, 2011 3 commits
  2. 15 Mar, 2011 2 commits
    • Mathieu Desnoyers's avatar
      x86: stop_machine_text_poke() should issue sync_core() · 0e00f7ae
      Mathieu Desnoyers authored
      Intel Archiecture Software Developer's Manual section 7.1.3 specifies that a
      core serializing instruction such as "cpuid" should be executed on _each_ core
      before the new instruction is made visible.
      
      Failure to do so can lead to unspecified behavior (Intel XMC erratas include
      General Protection Fault in the list), so we should avoid this at all cost.
      
      This problem can affect modified code executed by interrupt handlers after
      interrupt are re-enabled at the end of stop_machine, because no core serializing
      instruction is executed between the code modification and the moment interrupts
      are reenabled.
      
      Because stop_machine_text_poke performs the text modification from the first CPU
      decrementing stop_machine_first, modified code executed in thread context is
      also affected by this problem. To explain why, we have to split the CPUs in two
      categories: the CPU that initiates the text modification (calls text_poke_smp)
      and all the others. The scheduler, executed on all other CPUs after
      stop_machine, issues an "iret" core serializing instruction, and therefore
      handles core serialization for all these CPUs. However, the text modification
      initiator can continue its execution on the same thread and access the modified
      text without any scheduler call. Given that the CPU that initiates the code
      modification is not guaranteed to be the one actually performing the code
      modification, it falls into the XMC errata.
      
      Q: Isn't this executed from an IPI handler, which will return with IRET (a
         serializing instruction) anyway?
      A: No, now stop_machine uses per-cpu workqueue, so that handler will be
         executed from worker threads. There is no iret anymore.
      Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
      LKML-Reference: <20110303160137.GB1590@Krystal>
      Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
      Cc: <stable@kernel.org>
      Cc: Arjan van de Ven <arjan@infradead.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
      0e00f7ae
    • Linus Torvalds's avatar
      Linux 2.6.38 · 521cb40b
      Linus Torvalds authored
      521cb40b
  3. 14 Mar, 2011 35 commits