Date: Thu, 08 Feb 2007 21:06:19 -0800 From: Garrett Cooper <youshi10@u.washington.edu> To: freebsd-questions@freebsd.org Subject: Re: Trying to join an already exited pthread Message-ID: <45CC014B.9020303@u.washington.edu> In-Reply-To: <45CB38D8.1000706@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>
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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
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