[Bug nptl/1913] New: Thread blocked on sem_wait() does not unwind the C++ stack on thread cancellation.

["jordiblasi at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

/* 
  This simple .cpp source code tests if thread cancellation unwinds the C++ 
stack.  
  Assuming that C++/NPTL maps cancellation onto a language exception.   
  
  Shows that threads blocked in sem_wait() do not unwind the C++ stack. 
  However sleep(), pthread_testcancel(), ... behave as expected (throw 
exception). 
   
  compiled as g++ nptl_sem_cancel.cpp -lpthread 
   
  bug description: 
  =============== 
  Thread blocked on sem_wait() does not unwind the C++ stack on thread 
cancellation. 
  However cancellation is honored. 
   
  Execution under gdb yields to other conclusions. Thread cancellation lead to 
  SIG32 signal that interrupts sem_wait() system call that terminates the 
thread. 
 
  gdb a.out 
    GNU gdb 6.2-2mdk (Mandrakelinux) 
    Copyright 2004 Free Software Foundation, Inc. 
    GDB is free software, covered by the GNU General Public License, and you 
are 
    welcome to change it and/or distribute copies of it under certain 
conditions. 
    Type "show copying" to see the conditions. 
    There is absolutely no warranty for GDB.  Type "show warranty" for 
details. 
    This GDB was configured as "i586-mandrake-linux-gnu"...Using host 
libthread_db library "/lib/tls/libthread_db.so.1". 
     
    (gdb) r 
    Starting program: /home/user/a.out 
    [Thread debugging using libthread_db enabled] 
    [New Thread -1210851200 (LWP 19934)] 
    [New Thread -1210852432 (LWP 19937)] 
    Interrupted sem_wait?: Interrupted system call 
    Interrupted sem_wait?: Interrupted system call 
     
    Program received signal SIG32, Real-time event 32. 
    [Switching to Thread -1210852432 (LWP 19937)] 
    0xffffe410 in ?? () 
    (gdb) thread apply all bt 
     
    Thread 2 (Thread -1210852432 (LWP 19937)): 
    #0  0xffffe410 in ?? () 
    #1  0xb7d3daa8 in ?? () 
    #2  0x00000000 in ?? () 
    #3  0x00000000 in ?? () 
    #4  0xb7f66914 in sem_wait@GLIBC_2.0 () from /lib/tls/libpthread.so.0 
    #5  0xb7f6ba4c in __JCR_LIST__ () from /lib/tls/libpthread.so.0 
    #6  0x080487ef in cancel_thread () 
    #7  0xb7f62b3c in start_thread () from /lib/tls/libpthread.so.0 
    #8  0xb7dfe92a in clone () from /lib/tls/libc.so.6 
     
    Thread 1 (Thread -1210851200 (LWP 19934)): 
    #0  0xffffe410 in ?? () 
    #1  0xbfc95f58 in ?? () 
    #2  0x00004de1 in ?? () 
    #3  0x00000000 in ?? () 
    #4  0xb7f632e8 in pthread_join () from /lib/tls/libpthread.so.0 
    #5  0x0804895c in main () 
    #0  0xffffe410 in ?? () 
    (gdb) shared 
    Symbols already loaded for /lib/tls/libpthread.so.0 
    Symbols already loaded for /usr/lib/libstdc++.so.6 
    Symbols already loaded for /lib/tls/libm.so.6 
    Symbols already loaded for /lib/libgcc_s.so.1 
    Symbols already loaded for /lib/tls/libc.so.6 
    Symbols already loaded for /lib/ld-linux.so.2 
    (gdb) 
   
  environment: 
  ============ 
  uname -a 
  Linux wsc-linux8 2.6.12.6 #3 Wed Oct 5 12:27:21 CEST 2005 i686 Intel(R) 
Pentium(R) 4 CPU 3.20GHz unknown GNU/Linux 
   
  g++ --version 
  g++ (GCC) 3.4.1 (Mandrakelinux 10.1 3.4.1-4mdk) 
   
  ldd --version 
  ldd (GNU libc) 2.3.3 
   
  ldd ./a.out 
        linux-gate.so.1 =>  (0xffffe000) 
        libpthread.so.0 => /lib/tls/libpthread.so.0 (0xb7f51000) 
        libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0xb7e7f000) 
        libm.so.6 => /lib/tls/libm.so.6 (0xb7e5c000) 
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb7e53000) 
        libc.so.6 => /lib/tls/libc.so.6 (0xb7d33000) 
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0xb7f79000) 
 
  getconf GNU_LIBPTHREAD_VERSION         
  NPTL 2.3.3 
   
 */ 
 
#include <stdlib.h> 
#include <stdio.h> 
#include <pthread.h> 
#include <unistd.h> 
#include <errno.h> 
#include <exception> 
#include <semaphore.h> 
#include <string.h> 
 
sem_t sem; 
 
bool canceled; 
bool calls_destructor; 
bool exception_thrown; 
 
class MyMonitor { 
    public: 
        MyMonitor() {} 
        ~MyMonitor() {  
            calls_destructor = true;             
         } 
}; 
 
void *cancel_thread(void *arg) { 
     
    try {   
        MyMonitor m; 
 
        while(true)    // sleep(2); // pthread_testcancel(); 
            if(sem_wait(&sem) != 0)  
                printf("Interrupted sem_wait?: %s\n", strerror(errno)); 
         
        exit(2); 
         
    } catch (...) { 
        exception_thrown = true; 
        throw; 
    } 
     
    canceled = false; 
    return NULL; 
} 
 
int main() { 
     
    pthread_t cancel_thread_id; 
    canceled = calls_destructor = exception_thrown = false; 
     
    sem_init(&sem,0,0); 
     
    if ( pthread_create(&cancel_thread_id, NULL, &cancel_thread, NULL) != 0) { 
        printf("Cannot create 'cancel_thread'. %s\n", strerror(errno)); 
        exit(3); 
    } 
                     
    sleep(1);     
     
    if(pthread_cancel(cancel_thread_id)!=0) { 
        printf("Cannot cancel 'cancel_thread'. %s\n", strerror(errno)); 
        exit(4);         
    } 
     
    if(pthread_join(cancel_thread_id,NULL) != 0) { 
        printf("Cannot join 'cancel_thread'. %s\n", strerror(errno)); 
        exit(5); 
    } 
    else canceled = true; 
                 
    if(canceled)    printf("Thread canceled.\n"); 
    if(calls_destructor)    printf("Cancellation calls destructors.\n"); 
    if(exception_thrown)     printf("Cancellation throws exception.\n"); 
         
    return (canceled && calls_destructor && exception_thrown) ? EXIT_SUCCESS : 
6; 
}

-- 
           Summary: Thread blocked on sem_wait() does not unwind the C++
                    stack on thread cancellation.
           Product: glibc
           Version: 2.3.3
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
        AssignedTo: drepper at redhat dot com
        ReportedBy: jordiblasi at gmail dot com
                CC: glibc-bugs at sources dot redhat dot com
  GCC host triplet: i686 Intel(R) Pentium(R) 4 CPU 3.20GHz unknown GNU/Linux
                    2.6.12.


http://sourceware.org/bugzilla/show_bug.cgi?id=1913

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