Noah Watkins <[EMAIL PROTECTED]> writes: > [...] > The locks are aquired and released in each _start and _end marker, so > the equilibrium is not a issue.
But it becomes an issue should preemption, or control flow upset such as an early return or recursion, occurs between the start and end markers. > A more sane example is the insertion of values into a histogram. Instead > of the instrumenation point logging the values and having the histogram > constructed during a post-process step, data structures implemented the > histogrm are associated with the instrumenation point. The lock protects > this structure in a more intuitive way than the interval example. A better way may be to do what we do in systemtap scripts: in a interval-start type probe, store the start value in a table indexed by thread-id and nesting-level; in the interval-end type probe, find the corresponding value, compute the difference (as appropriate), and store the result only then into your long-term lookup table. This approach requires *no locks* to survive between start & end: the probes remain atomic. > I think most of problems involving non atomicity of the > connection/disconnection of probes can be accomplished by good house > keeping and settings things up in phases which insure consistency. A marker callback can take shortcuts, I guess, if it allows itself to make assumptions about the ways it can be called. I scanned over the thread, but still haven't seen a specific argument for extra marker-type annotations that would relate to this issue. What tool would need to scan the available markers, and how would extra information allow it to do its job? - FChE - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
