From owner-cvs-all  Mon Apr 16 19:44:39 2001
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From: John Baldwin <jhb@FreeBSD.org>
Date: Mon, 16 Apr 2001 19:44:36 -0700 (PDT)
To: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: cvs commit: src/sys/alpha/alpha exception.s
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jhb         2001/04/16 19:44:35 PDT

  Modified files:
    sys/alpha/alpha      exception.s 
  Log:
  In exception_return(), test for usermode before testing the IPL to see if
  we should call ast().  This allows us to branch to a separate Lkernelret
  label so we can fixup the saved t7 register in the trapframe.  Otherwise
  we can run into a problem on SMP systems where a process is interrupted by
  a trap or interrupt on one CPU, migrates to another CPU, and then returns
  with the t7 in the stack clobbering the CPU's t7.  As a result, two CPU's
  would both point to the same per-CPU data and things would go downhill from
  there.
  
  Sleuthing help by:	gallatin
  
  Revision  Changes    Path
  1.8       +8 -4      src/sys/alpha/alpha/exception.s


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