Date: Sat, 27 Nov 2004 12:08:57 +0300 From: Alexander Bubnov <alek@mts-nn.ru> To: =?ISO-8859-1?Q?Mikko_Ty=F6l=E4j=E4rvi?= <mbsd@pacbell.net> Cc: freebsd-threads@freebsd.org Subject: Re: deadlock Message-ID: <41A84429.8010805@mts-nn.ru> In-Reply-To: <20041126143048.U9837@sotec.home> References: <41A72410.9080500@mail.ru> <20041126143048.U9837@sotec.home>
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Many thanks! Mikko Tyo"la"ja"rvi wrote: > > Hi Alexander, > > On Fri, 26 Nov 2004, Alexander Bubnov wrote: > >> /* >> Hello! >> Could you tell me why this exemple is deadlocked under FreeBSD, not >> Linux? >> (FreeBSD 4.10 and 5.2 , I have not tried under other versions) >> >> a string that includes this problem marked, see below the main function >> >> */ >> #include<sys/types.h> >> #include<sys/ipc.h> >> #include<sys/sem.h> >> #include<errno.h> >> #include<pthread.h> >> #include<stdlib.h> >> #include<stdio.h> >> >> int Exit=0;/* uses in hand(), changes in main() */ >> int ReStart,Start;/* semaphores ID which returns semget() */ >> /* >> Start semphore controls starting threads, >> EXETHREADS - how many threads can start in one time >> ReStart semaphore for wait when the starting threads display a string >> */ >> struct sembuf dec={0},inc={0},op={0};/* they initilize in the main >> function*/ >> void*hand(void*p){ >> do{ >> semop(Start,&dec,1); >> if(Exit)break; >> puts(p); >> semop(ReStart,&inc,1); >> }while(1); >> fprintf(stderr,"bye, %s!\n",p); >> return NULL; >> } >> >> #define MAXTHREADS 5 >> #define EXETHREADS 2 /* number of threads which is executed in one >> time*/ >> #define ITERAT 2 /* number of iterations, see the main function */ >> >> int main(void){ >> char*s[MAXTHREADS]={"Mike","Leo","Don","Raph","Splinter"}; >> int i; >> pthread_t thread[MAXTHREADS]; >> /* to initlize semaphores operations */ >> dec.sem_op=-1,inc.sem_op=1,op.sem_op=EXETHREADS; >> if( -1==(Start=semget('A',1,0666|IPC_CREAT)) || >> -1==(ReStart=semget('B',1,0666|IPC_CREAT)) >> ){perror("semget");return EXIT_FAILURE;} >> /* to initilize semaphores value */ >> semctl(Start,0,SETVAL,0); >> semctl(ReStart,0,SETVAL,0); >> #ifndef linux /* may be this string is not needed, I do not know*/ >> if(pthread_setconcurrency(MAXTHREADS+1))perror("concurrency"); >> #endif > > > Not needed. Also, it does not set errno, it returns the error value. > Use strerror(). > >> >> /* to create the threads */ >> for(i=0;i<MAXTHREADS;++i) >> pthread_create(thread+i,NULL,hand,s[i]); >> for(i=0;i<ITERAT;++i){ >> puts("____START____"); >> semop(Start,&op,1); >> /* to wait EXETHREADS threads */ >> op.sem_op*=-1; >> /* >> !!! this problem is here !!! >> if I insert 'pause()' or 'while(1)' instend of 'semop(ReStart,&op,1)' >> that only one thread is executed two time, why? >> this code does not help too (but I can see names that is printed by >> hand()) >> op.sem_flg=IPC_NOWAIT >> while(-1==semop(ReStart,&op,1) && EAGAIN); >> */ >> semop(ReStart,&op,1); >> op.sem_op*=-1; >> puts("____FINISH____"); >> } >> /* to wait the threads to exit*/ >> semctl(Start,0,SETVAL,MAXTHREADS); >> Exit=1; >> for(i=0;i<MAXTHREADS;++i) >> pthread_join(thread[i],NULL); >> >> if( -1==semctl(ReStart,0,IPC_RMID) || >> -1==semctl(Start,0,IPC_RMID) >> ) perror("semdel"); >> return EXIT_SUCCESS; >> } > > > Silently wondering why on earth anybody would want to use SYSV > semaphores to synchronize threads in the same program, I compiled and > ran your code on some different boxes: > > FreeBSD 5.3, i386 - runs ok (?) > FreeBSD 5.3, sparc64 - hangs after first line of output > Linux 2.6/Debian 3.1, i386 - hangs after last line of output > Solaris 9, sparc64 - dumps core in semctl > > I believe your program perhaps is not 100% correct... :-) > > $.02, > /Mikko > _______________________________________________ > freebsd-threads@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-threads > To unsubscribe, send any mail to > "freebsd-threads-unsubscribe@freebsd.org" > >
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