threads/81258: Thread specific data is sometimes assigned to
multiple keys and/or threads
deischen at freebsd.org
Thu May 19 05:52:25 PDT 2005
On Thu, 19 May 2005, Jens Nilsson wrote:
> Thread specific data is sometimes assinged to multiple keys
> and/or threads. In the attached test program two threads getting
> the same tsd for the same key seems to be the most usual.
> Run the attached test program a couple of times. One of the
> threads will wait for input, the bug is most likely to show up if
> enter is pressed in about half a second after the thread asked
> for data.
> I ran into the bug some time ago while developing a bit more
> complex application that involved a couple of threads all of them
> with TSD and some doing RPC-calls. In that application I had the
> same problem with any of the thread libs libpthread, libthr, and
> libc_r. This test program only seems to be able to repeat the
> problem with libpthread.
Thread-specific data is destroyed when the thread exits. Your
TSD is allocated using malloc() and destroyed using free(). Your
test program does nothing to ensure that all threads have started
running and have all created/initialized their TSD before the
first thread exits. malloc() is probably reusing a prior
allocation that has been free()'d.
Thread exiting != Thread being joined.
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