Date: Thu, 08 Feb 2007 21:29:07 -0800 From: Garrett Cooper <youshi10@u.washington.edu> To: freebsd-hackers@freebsd.org Subject: Re: Trying to join an already exited pthread Message-ID: <45CC06A3.5080909@u.washington.edu> In-Reply-To: <45CC01B0.8050502@u.washington.edu> References: <Pine.LNX.4.43.0702071314560.22034@hymn08.u.washington.edu> <eqdhl2$1tmb$1@wattres.Watt.COM> <87D4B047-DC72-427B-863F-A082C3A4E5CD@u.washington.edu> <45CB38D8.1000706@u.washington.edu> <45CC014B.9020303@u.washington.edu> <45CC01B0.8050502@u.washington.edu>
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Garrett Cooper wrote: > Garrett Cooper wrote: >> Garrett Cooper wrote: >>> Garrett Cooper wrote: >>>> On Feb 7, 2007, at 1:51 PM, Steve Watt wrote: >>>> >>>>> In <Pine.LNX.4.43.0702071314560.22034@hymn08.u.washington.edu>, >>>>> <youshi10@u.washington.edu> wrote: >>>>>> Just wondering: >>>>>> >>>>>> If I was to try and join a pthread that already exited, would >>>>>> there be an error >>>>>> message output and/or errno set to an error value, or would a >>>>>> system hang? >>>>> >>>>> Was the thread created with detach state set >>>>> PTHREAD_CREATE_DETACHED or >>>>> PTHREAD_CREATE_JOINABLE? If it was PTHREAD_CREATE_JOINABLE, has the >>>>> thread already been joined? >>>>> >>>>> You should be able to join a thread that was created joinable, only >>>>> once. >>>>> If you join it again, or join a thread that was created detached, the >>>>> results are unspecified in POSIX. There is an error status that may >>>>> be returned, but it may do other bad things to your system. >>>>> >>>>> Note that pthread_join doesn't set errno; it returns an error value >>>>> directly. I would never expect the system to hang, though the >>>>> application >>>>> might. If your application is hanging, make sure that you're not >>>>> trying >>>>> to call pthread_join from within a signal handler. >>>>> >>>>>> It this variable on Unix OSes? >>>>> >>>>> That the results are unspecified? No. What "unspecified" means? >>>>> Absolutely. >>>>> --Steve Watt KD6GGD PP-ASEL-IA ICBM: 121W 56' 57.5" / 37N >>>>> 20' 15.3" >>>>> Internet: steve @ Watt.COM Whois: SW32-ARIN >>>>> Free time? There's no such thing. It just comes in varying >>>>> prices... >>>> >>>> I asked this because I was short on time and so was the person >>>> who asked me earlier. I'm going to try giving the pthread exit and >>>> join a shot just to see whether or not this is true or not and then >>>> I'll report my results to the list. >>>> Thanks for the insight though--hopefully my results will yield a >>>> solid positive or negative to this being a problem. >>>> -Garrett >>> >>> Under Suse Linux there were absolutely no errors when I tried to do >>> this. I'll post a code snippet later. >>> -Garrett >> >> Ok, here's a link to my code: >> >> http://students.washington.edu/youshi10/posted/thread_test.c >> >> My results (FreeBSD): >> >> [root@hoover /home/gcooper]# ./tt >> Thread join detached >> Thread kill detached >> Joined thread yielded error code: 2 >> Trying to join the already joined thread yields error code: 0 >> >> My results (Suse Linux): >> >> # ./tt >> Thread join detached >> Thread kill detached >> Joined thread yielded error code: 0 >> Trying to join the already joined thread yields error code: 0 >> >> That was sure interesting.. is it supposed to error out or was it the >> remnant of an old error call? >> >> Probably the latter, but I was just curious.. >> >> -Garrett Actually, now that I think about it the calls I made with ps in the program are valid for Linux but not for FreeBSD (they're for getting thread listings). Hence error code 2. From intro(2): 2 ENOENT No such file or directory. A component of a specified pathname did not exist, or the pathname was an empty string. Didn't think that a bad command would return errno=2 though.. -Garrett
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