Re: [Linux-ia64] ptrace behavior accessing ar.lc and ar.ec

[David Mosberger <davidm@hpl.hp.com>]

 > Hi folks,
 > I'm using the ptrace interface to create a
 > "architectural" processor state tracing tool.  When I
 > access AR.LC and AR.EC, I *usually* get the expected
 > result, but every once and a while it returns a bogus
 > result.

 > Is there a known bug, or am I using ptrace
 > incorrectly?

Not a known bug.

 > Here's how its used:
 > lc = ptrace (PTRACE_PEEKUSER, state->pid, PT_AR_LC,
 > 0);

 > The tracing program observes some sort of behavior
 > like:

 > mov.i ar.lc = r61    (I'm pretty sure r61 is 6), and  
 >                        ptrace returns 0 
 > sxt4  r22=r60        ptrace returns -1
 > .....                "
 > (swp kernel code)    "
 > .....                "
 > br.ctop.sptk.few .b9 ptrace returns -1, br taken 
 > (p17) st8 [r15]=r34  ptrace returns 5

Do you have a self-contained and small test program that reproduces
the problem?  That would make it easier to investigate the problem.

	--david