Commit fd992dee authored by Nick Mathewson's avatar Nick Mathewson 🤹
Browse files

Don't attempt to log messages to a controller from a worker thread. 

This patch adds a function to determine whether we're in the main
thread, and changes control_event_logmsg() to return immediately if
we're in a subthread.  This is necessary because otherwise we will
call connection_write_to_buf, which modifies non-locked data
structures.

Bugfix on 0.2.0.x; fix for at least one of the things currently
called "bug 977".
parent d66c3797

ChangeLog

+3 −0
Original line number Diff line number Diff line
@@ -5,6 +5,9 @@ Changes in version 0.2.1.16-?? - 2009-??-?? 
    - Don't warn users about low port and hibernation mix when they

      provide a *ListenAddress directive to fix that. Bugfix on

      0.2.1.15-rc.

    - Fix a race condition that could cause crashes or memory

      corruption when running as a server with a controller listening

      for log messages.



  o Minor bugfixes (on 0.2.1.x):

    - When switching back and forth between bridge mode, do not start

src/common/compat.c

+19 −0
Original line number Diff line number Diff line
@@ -2076,6 +2076,7 @@ tor_threads_init(void) 
    pthread_mutexattr_init(&attr_reentrant);

    pthread_mutexattr_settype(&attr_reentrant, PTHREAD_MUTEX_RECURSIVE);

    threads_initialized = 1;

    set_main_thread();

  }

}

#elif defined(USE_WIN32_THREADS)
@@ -2168,9 +2169,27 @@ tor_threads_init(void) 
#if 0

  cond_event_tls_index = TlsAlloc();

#endif

  set_main_thread();

}

#endif



/** Identity of the "main" thread */

static unsigned long main_thread_id = -1;



/** Start considering the current thread to be the 'main thread'.  This has

 * no effect on anything besides in_main_thread(). */

void

set_main_thread(void)

{

  main_thread_id = tor_get_thread_id();

}

/** Return true iff called from the main thread. */

int

in_main_thread(void)

{

  return main_thread_id == tor_get_thread_id();

}



/**

 * On Windows, WSAEWOULDBLOCK is not always correct: when you see it,

 * you need to ask the socket for its actual errno.  Also, you need to

src/common/compat.h

+3 −0
Original line number Diff line number Diff line
@@ -522,6 +522,9 @@ void tor_threads_init(void); 
#define tor_threads_init() STMT_NIL

#endif



void set_main_thread(void);

int in_main_thread(void);



#ifdef TOR_IS_MULTITHREADED

#if 0

typedef struct tor_cond_t tor_cond_t;

src/common/util.c

+2 −0
Original line number Diff line number Diff line
@@ -2480,6 +2480,8 @@ start_daemon(void) 
    if (fork() != 0) {

      exit(0);

    }

    set_main_thread(); /* We are now the main thread. */



    return;

  }

}

src/or/control.c

+5 −0
Original line number Diff line number Diff line
@@ -3367,6 +3367,11 @@ control_event_logmsg(int severity, uint32_t domain, const char *msg) 
{

  int event;



  /* Don't even think of trying to add stuff to a buffer from a cpuworker

   * thread. */

  if (! in_main_thread())

    return;



  if (disable_log_messages)

    return;