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Date: Thu, 13 Aug 1998 11:00:01 -0700 (PDT)
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To: freebsd-bugs@FreeBSD.ORG
From: Jin Guojun (ITG staff) <jin@george.lbl.gov>
Subject: Re: misc/7600: Pthreads Bug - Interaction between printf and pthread_self
Reply-To: Jin Guojun (ITG staff) <jin@george.lbl.gov>
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The following reply was made to PR misc/7600; it has been noted by GNATS.

From: Jin Guojun (ITG staff) <jin@george.lbl.gov>
To: FreeBSD-gnats-submit@FreeBSD.ORG, loschert@servint.com
Cc:  Subject: Re: misc/7600: Pthreads Bug - Interaction between printf and pthread_self
Date: Thu, 13 Aug 1998 10:53:24 -0700 (PDT)

 The problem is no in "3 Exit the shell.". It is related to either rexec/rsh
 or xterm.
 I tried followings, and only exit xterm will cause the same problem:
 
 % sh
 $ ./bug &
 ^D
 % top # everything is OK
 
 % csh
 % ./bug &
 %^D
 % top # everything is OK
 % exit
 
 then log back in, bug is chewing CPU now.
 
 	-Jin
 
 > >Description:
 >  
 > While testing a couple of server apps that I had written, I discovered that in c
 > ertain situations, the process would "run-away".  At that point, the app could o
 > nly be killed with a kill -9 and top would show that the process was eating up 9
 > 9.9% of the cpu cycles.
 >  
 > I found that the condition that instigated the problem was starting the app as a
 >  background process and then exiting the shell.  Almost immediately after exitin
 > g the shell, the process would go haywire. :)
 >  
 > The apps use pthreads and therefore -libc_r.
 >  
 > I attempted to isolate the problem this evening by stripping out extraneous code
 > .  I was able to cut it down to the following program.  The line that it does no
 > t like is the printf line that calls pthread_self to show the thread id.
 >  
 >  
 > >How-To-Repeat:
 >  
 > 1. Compile the below code with the following command:
 >  
 >         gcc -Wall -o bug FILENAME.c -lc_r
 >  
 > 2. Run the program in the background with:
 >  
 >         ./bug &
 >  
 > 3. Exit the shell.
 >  
 > 4. Log back in, check cpu usage with top.
 >  
 >  
 >  
 > ----CODE BEGINS (FILENAME.c)----
 >  
 >  
 > #include <stdio.h>
 > #include <unistd.h>
 > #include <pthread.h>
 >  
 > void     *newthread    (void *vptr);
 >  
 >  
 > int main()
 > {
 >      pthread_t      thread;
 >  
 >      pthread_create (&thread, NULL, newthread, NULL);
 >      pthread_join   (thread, NULL);
 >      exit(0);
 > }
 >  
 >  
 > void *newthread(void *vptr)
 > {
 >      for(;;) {
 >           printf("Thread %d: Just looped again.\n", (int) pthread_self());
 >           sleep(5);
 >      }
 > }
 >  
 >  
 > ----CODE ENDS----

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