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Re: [PATCH] Fix mutex pretty printer test and pretty printer output.
2017-01-11 7:32 GMT-03:00 Torvald Riegel <triegel@redhat.com>:
> Do you have a concrete suggestion for alternative wording, or do you
> think that "(if known)" is okay?
Perhaps there could be a check for __owner being zero, and in that
case print "unknown" instead of "0". That way we could drop the "(if
known)". Maybe we could check whether __elision exists and inform the
user that lock elision is enabled, so that they have a better idea of
what's going on. What do you think?
> Maybe. If you want to go ahead and explain what the pretty printers
> reveal, and how they should not be misunderstood (which is an important
> part of this -- users should be aware that they get simplified
> information), then please propose a patch.
There wouldn't be a need for further explanation if we just said that
the owner is unknown to us when __owner is zero.
> It might also be worth to clearly state the design goals for the pretty
> printers, which in my opinion is roughly:
> * Provide simplified information about the state of synchronization
> constructs to users.
> * There is no guarantee that this information is complete and covers
> everything a particular thread might do (e.g., the pretty printers do
> not show if a thread is spin-waiting in an attempt to acquire a mutex).
> * It is not aimed at understanding the details of the implementation of
> the synchronization construct.
I thought that was implicitly clear. Printers exist precisely to
abstract away the implementation details of the sync constructs, and
yes, some details might be left off. If the user wants to know what's
going on under the hood, they can just disable the printers and try to
make sense of what gdb shows.