[Bug translator/7033] New: Optimize locking reginon of global variables

[Bug translator/7033] New: Optimize locking reginon of global variables

[mhiramat at redhat dot com]

Currently, systemtap locks whole of a probe handler which uses global variables.
However, I think translator can shrink the locking region to the best size.

{ 
 (lock(a) and lock(b))
 ...
 a = xxx  <- only here, we actually needs a's lock.
 ...
 if (yyy)
   b = zzz <- only here, we actually needs b's lock.
 ...
 (unlock(a) and unlock(b))
}

-- 
           Summary: Optimize locking reginon of global variables
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: translator
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: mhiramat at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=7033

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[Bug translator/7033] Optimize locking reginon of global variables

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-11-14 23:42 -------
A long time ago, this is how we used to do things.
Some reasons against it:

- generated code was much longer, as each use of those
  globals had to be protected individually
- greater likelihood of deadlocks (which would be detected by
  *trylock timeout loops, but that still takes time)
- by the time such a deadlock is detected, we can't roll back
  the prior code run by the probe handler, so we end up with
  inconsistent state


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


http://sourceware.org/bugzilla/show_bug.cgi?id=7033

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[Bug translator/7033] Optimize locking reginon of global variables

[fche at redhat dot com]

------- Additional Comments From fche at redhat dot com  2008-11-27 17:11 -------
For the reasons listed above, this idea is probably not worth pursuing.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |WORKSFORME


http://sourceware.org/bugzilla/show_bug.cgi?id=7033

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