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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 12 May 2010 10:29:35 +0000 (UTC)
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Subject: cvs commit: src/sys/amd64/amd64 apic_vector.S exception.S
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kib         2010-05-12 10:29:35 UTC

  FreeBSD src repository

  Modified files:
    sys/amd64/amd64      apic_vector.S exception.S 
  Log:
  SVN rev 207958 on 2010-05-12 10:29:35Z by kib
  
  Route all returns from the interrupts and faults through the doreti_iret
  labeled iretq instruction.
  
  Suppose that multithreaded process executes two threads, currently
  scheduled on different processors. Let assume that thread A executes
  using %cs or %ss pointing into the descriptor from LDT. If IPI comes
  which handler does not return by jump to doreti, and meantime thread B
  invalidates descriptor pointed to by %cs or %ss, then iretq from IPI
  handler could fault.
  
  Routing the return by doreti_iret allows kernel to catch the situation
  and recover from it by sending signal to the usermode.
  
  Tested by:      pho
  MFC after:      1 week
  
  Revision  Changes    Path
  1.114     +7 -6      src/sys/amd64/amd64/apic_vector.S
  1.146     +1 -1      src/sys/amd64/amd64/exception.S