RE: [patch] ia64: fix potential NaT bit error for sys_pipe().

From: David Mosberger <davidm_at_napali.hpl.hp.com>
Date: 2005-01-21 10:51:22
>>>>> On Thu, 20 Jan 2005 15:22:59 -0800, "Seth, Rohit" <rohit.seth@intel.com> said:

  Rohit> We are also thinking of reseting the mfh bit on every syscall
  Rohit> entry as an optimization.

  Rohit> Comments?

Sounds OK with me.  We should delete this comment from process.c then,
too:

        /*
         * NOTE: The calling convention considers all floating point
         * registers in the high partition (fph) to be scratch.  Since
         * the only way to get to this point is through a system call,
         * we know that the values in fph are all dead.  Hence, there
         * is no need to inherit the fph state from the parent to the
         * child and all we have to do is to make sure that
         * IA64_THREAD_FPH_VALID is cleared in the child.
         *
         * XXX We could push this optimization a bit further by
         * clearing IA64_THREAD_FPH_VALID on ANY system call.
         * However, it's not clear this is worth doing.  Also, it
         * would be a slight deviation from the normal Linux system
         * call behavior where scratch registers are preserved across
         * system calls (unless used by the system call itself).
         */

and change:

#define THREAD_FLAGS_TO_CLEAR (IA64_THREAD_FPH_VALID | IA64_THREAD_DBG_VALID \
                               | IA64_THREAD_PM_VALID)

to:

#define THREAD_FLAGS_TO_CLEAR (IA64_THREAD_DBG_VALID | IA64_THREAD_PM_VALID)

	--david
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Received on Thu Jan 20 18:54:15 2005

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