Commit 9f37ea45 authored by unknown's avatar unknown
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BUG#24507 (rpl_log.test crash slave): 

The problem was located to lie inside current NPTL pthread_exit() 
implementation. Race conditions in this code can lead to segmentation
fault. Hovewer, this can happen only in a race between first thread 
calling pthread_exit() and other threads. 

Workaround implemented in this patch spawns a dummy thread, which
exits immediately, during thread lib initialization. This will exclude
segment violations when further threads exit.
 


include/my_pthread.h:
  define macro NPTL_PTHREAD_EXIT_BUG which controls whether workaround
  in my_thread_global_init() is included or not.
mysys/my_thr_init.c:
  Spawn a dummy thread in my_thread_global_init() to initialize pthread 
  lib internal variables.
parent 00fec63a

include/my_pthread.h

+20 −0
Original line number Diff line number Diff line
@@ -31,6 +31,26 @@ extern "C" { 
#define EXTERNC

#endif /* __cplusplus */ 



/*

  BUG#24507: Race conditions inside current NPTL pthread_exit() implementation.

  

  If macro NPTL_PTHREAD_EXIT_HACK is defined then a hack described in the bug

  report will be implemented inside my_thread_global_init() in my_thr_init.c.

   

  This amounts to spawning a dummy thread which does nothing but executes 

  pthread_exit(0). 

  

  This bug is fixed in version 2.5 of glibc library.

  

  TODO: Remove this code when fixed versions of glibc6 are in common use. 

 */



#if defined(TARGET_OS_LINUX) && defined(HAVE_NPTL) &&

    defined(__GLIBC__) && ( __GLIBC__ < 2 || __GLIBC__ == 2 && __GLIBC_MINOR__ < 5 )

#define NPTL_PTHREAD_EXIT_BUG	1

#endif 





#if defined(__WIN__) || defined(OS2)



#ifdef OS2

mysys/my_thr_init.c

+39 −0
Original line number Diff line number Diff line
@@ -44,6 +44,23 @@ pthread_mutexattr_t my_fast_mutexattr; 
pthread_mutexattr_t my_errorcheck_mutexattr;

#endif



#ifdef NPTL_PTHREAD_EXIT_BUG /* see my_pthread.h */



/*

 Dummy thread spawned in my_thread_global_init() below to avoid

 race conditions in NPTL pthread_exit code.

*/



static

pthread_handler_t nptl_pthread_exit_hack_handler(void *arg)

{

  /* Do nothing! */

  pthread_exit(0);

  return 0;

}



#endif



/*

  initialize thread environment
@@ -63,6 +80,28 @@ my_bool my_thread_global_init(void) 
    return 1;

  }

  

#ifdef NPTL_PTHREAD_EXIT_BUG



/*

  BUG#24507: Race conditions inside current NPTL pthread_exit() implementation.



  To avoid a possible segmentation fault during concurrent executions of 

  pthread_exit(), a dummy thread is spawned which initializes internal variables

  of pthread lib. See bug description for thoroughfull explanation. 

  

  TODO: Remove this code when fixed versions of glibc6 are in common use. 

*/



  pthread_t       dummy_thread;

  pthread_attr_t  dummy_thread_attr;



  pthread_attr_init(&dummy_thread_attr);

  pthread_attr_setdetachstate(&dummy_thread_attr,PTHREAD_CREATE_DETACHED);



  pthread_create(&dummy_thread,&dummy_thread_attr,nptl_pthread_exit_hack_handler,NULL);



#endif



#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP

  /*

    Set mutex type to "fast" a.k.a "adaptive"