Re: [PATCH 1/7] cpu-timers: high-resolution CPU clocks for POSIX clock_* syscalls

[Ulrich Drepper <drepper@redhat.com>]

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Christoph Lameter wrote:

> Posix does not prescribe any access limitations for those clocks and as
> far as I understand the standard, access to all process clocks needs to
> be possible.

And how exactly do you plan to address clocks of various threads in 
another process?  Threads are only identified by the pthread_t 
descriptor.  These values have no meaning outside the process the 
threads are in.  The TIDs we use in the implementation cannot be used. 
They are an implementation detail and a thread might very well have 
different TIDs over time in future versions of the thread library.

The pthread_getcpuclockid() and similar uses return clock IDs which are 
only meaningful in the calling process.  Using the value in another 
process has undefined results.  I.e., what Roland says is correct, the 
limitation is needed.

-- 
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖

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