Messages in this thread | | | Date | Tue, 13 Nov 2007 23:25:34 +0100 | From | Andi Kleen <> | Subject | Re: [perfmon] Re: [perfmon2] perfmon2 merge news |
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On Tue, Nov 13, 2007 at 02:22:34PM -0800, Stephane Eranian wrote: > Andi, > On Tue, Nov 13, 2007 at 10:50:56PM +0100, Andi Kleen wrote: > > > Yes, horribly more complicated because of locking issues within perfmon. > > > As soon as you expose a file descriptor, you need some locking to prevent > > > multiple user threads (malicious or not) to compete to access the PMU state. > > > > Why do you need the file descriptor? > > > > To identify your monitoring session be it system-wide (i.e., per-cpu) or per-thread. > file descriptor allows you to use close, read, select, poll and you leverage the
Surely that could be done with a flag for each call too? Keeping file descriptors to pass essentially a boolean seems overkill.
> existing file descriptor sharing/inheritance sematics. At the kernel level, a > descriptor provides all the callback necessary to make sure you clean up the perfmon > session state on exit.
Didn't you already have a thread destructor for it?
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