Re: Stats collection on Windows

On Tue, Apr 04, 2006 at 11:17:49PM -0400, Tom Lane wrote:
> "Qingqing Zhou" <zhouqq(at)cs(dot)toronto(dot)edu> writes:
> > "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote
> >> Redmond crowd should be able to figure out that recycling process IDs
> >> instantly would be a stupid idea...)
> > Can you explain more of this? IMHO, if we rely on feature like this, the
> > difference is unstable-every-day vs. unstable-every-year.
> The mere existence of the kill() primitive should bring to mind reasons
> why it's a bad idea.

CreateProcess - "The process is assigned a process identifier. The
identifier is valid until the process terminates. It can be used to
identify the process, or specified in the OpenProcess function to open
a handle to the process. The initial thread in the process is also
assigned a thread identifier. ..."

TerminateProcess - "Terminates the specified process and all of its
threads."

TerminateProcess takes a HANDLE, not a process identifier. Yes, they
provide the "kill" primitive, but only as a compatibility measure. A
"good" Windows process, should maintain a HANDLE to the process, and
kill the process using the HANDLE. This way, there is no race. The
HANDLE is also how you wait for the process to terminate normally.

I prefer the "Redmond" way, in that I find UNIX's use of integer
identifiers to be encouraging of race conditions. UNIX requires hacks
like minimizing PID reuse, because UNIX is the one that is broken. :-)

Cheers,
mark

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