audioscrobbler deadlocks

Audioscrobbler randomly deadlocks, possibly due to bad use of condition variables code.

The main loop waits until it is signaled: http://trac.videolan.org/vlc/browser/trunk/modules/misc/audioscrobbler.c?rev=24489#L270

The signaling occurs in a callback on input "state" : http://trac.videolan.org/vlc/browser/trunk/modules/misc/audioscrobbler.c?rev=24489#L621

using a little patch to get more verbose debug (with --verbose -1 to not have debug for other modules), I get:

lock&wait

Audioscrobbler object locked: ../../trunk/src/misc/objects.c 463

object signaling

Audioscrobbler object locked: ../../trunk/src/misc/objects.c 463

added Component::Interface: other plugins Severity::major Type::bug Version::master git + 1 deleted label

changed milestone to %0.9.0 features freeze

to get usefull verbose debug

Added attachment:

• audioscrobbler_debug.diff

(In [24521]) Cleanup condition handling, should fix #1448 (closed)

added Status::fixed label

closed

Still randomly deadlocks when an input has ended

(gdb) thread apply all bt

Thread 11 (Thread 0x28601100 (LWP 100152)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x2835459b in _umtx_op () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830b7fd in pthread_cleanup_push () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x28309260 in pthread_kill () from /lib/libthr.so.3
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x2811ae50 in __vlc_thread_join (p_this=0x2867b080, 
    psz_file=0x28141bb8 "../../trunk/src/libvlc-common.c", i_line=1114)
    at ../../trunk/src/misc/threads.c:836
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x2808e138 in libvlc_InternalAddIntf (p_libvlc=0x28638030, psz_module=0x0, 
    b_block=1, b_play=1, i_options=0, ppsz_options=0x0)
    at ../../trunk/src/libvlc-common.c:1114
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x2808def9 in VLC_AddIntf (i_object=0, psz_module=0x0, b_block=1, b_play=1)
    at ../../trunk/src/libvlc.c:145
[#6](https://code.videolan.org/videolan/vlc/-/issues/6)  0x08048f3b in main (i_argc=6, ppsz_argv=0xbfbfe9a8)
    at ../trunk/src/vlc.c:215

Thread 10 (Thread 0x28601200 (LWP 100151)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x283548bb in sigwait () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x28305e64 in sigwait () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x0804912c in SigHandler (data=0x28601200) at ../trunk/src/vlc.c:260
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x00000000 in ?? ()

---Type <return> to continue, or q <return> to quit---
Thread 9 (Thread 0x28601e00 (LWP 100162)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x2835459b in _umtx_op () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830b9b8 in pthread_cleanup_push () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x2830a1be in pthread_cond_init () from /lib/libthr.so.3
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x280a2d2a in playlist_PreparseLoop (p_obj=0x28617a90)
    at vlc_threads_funcs.h:501
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x2809e37a in RunPreparse (p_obj=0x28617a90)
    at ../../trunk/src/playlist/thread.c:222
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#6](https://code.videolan.org/videolan/vlc/-/issues/6)  0x00000000 in ?? ()

Thread 8 (Thread 0x28601f00 (LWP 100166)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x2835459b in _umtx_op () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830b9b8 in pthread_cleanup_push () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x2830a1be in pthread_cond_init () from /lib/libthr.so.3
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x280a1dc4 in playlist_FetcherLoop (p_obj=0x28657690)
    at vlc_threads_funcs.h:501
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x2809e33a in RunFetcher (p_obj=0x28657690)
    at ../../trunk/src/playlist/thread.c:229
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#6](https://code.videolan.org/videolan/vlc/-/issues/6)  0x00000000 in ?? ()

Thread 7 (Thread 0x28602000 (LWP 100196)):
---Type <return> to continue, or q <return> to quit---
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x2835459b in _umtx_op () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830b9b8 in pthread_cleanup_push () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x2830a1be in pthread_cond_init () from /lib/libthr.so.3
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x2809e301 in RunControlThread (p_playlist=0x28802700)
    at vlc_threads_funcs.h:501
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x00000000 in ?? ()

Thread 6 (Thread 0x28602100 (LWP 100197)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x283e6633 in read () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x283026f2 in read () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x2812a509 in __vlc_object_wait (obj=0x2867ad40)
    at ../../trunk/src/misc/objects.c:602
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x285af432 in Run (p_intf=0x2867ad40)
    at ../../../trunk/modules/misc/audioscrobbler.c:284
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x2809bcaf in RunInterface (p_intf=0x2867ad40)
    at ../../trunk/src/interface/interface.c:277
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#6](https://code.videolan.org/videolan/vlc/-/issues/6)  0x00000000 in ?? ()

Thread 5 (Thread 0x28602200 (LWP 100198)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x2835459b in _umtx_op () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830b9b8 in pthread_cleanup_push () from /lib/libthr.so.3
---Type <return> to continue, or q <return> to quit---
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x2830a1be in pthread_cond_init () from /lib/libthr.so.3
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x2812a65e in __vlc_object_wait (obj=0x2867afb0) at vlc_threads_funcs.h:501
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x285b52db in Run (p_intf=0x2867afb0) at vlc_objects.h:195
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x2809bcaf in RunInterface (p_intf=0x2867afb0)
    at ../../trunk/src/interface/interface.c:277
[#6](https://code.videolan.org/videolan/vlc/-/issues/6)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#7](https://code.videolan.org/videolan/vlc/-/issues/7)  0x00000000 in ?? ()

Thread 4 (Thread 0x28602500 (LWP 100199)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x283c910f in nanosleep () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830288b in nanosleep () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x28111f3c in msleep (delay=50000) at ../../trunk/src/misc/mtime.c:342
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x285c0c9f in Run (p_intf=0x2867b080)
    at ../../../trunk/modules/gui/ncurses.c:399
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x2809bcaf in RunInterface (p_intf=0x2867b080)
    at ../../trunk/src/interface/interface.c:277
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#6](https://code.videolan.org/videolan/vlc/-/issues/6)  0x00000000 in ?? ()

Thread 3 (Thread 0x28602700 (LWP 100157)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x2835459b in _umtx_op () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830ba8d in pthread_cleanup_push () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x28307390 in pthread_mutex_getprioceiling () from /lib/libthr.so.3
---Type <return> to continue, or q <return> to quit---
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x2812ac28 in __vlc_object_lock (obj=0x2867ad40) at vlc_threads_funcs.h:136
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x285b1484 in PlayingChange (p_this=0x28657c10, 
    psz_var=0x2814cdca "state", oldval=
        {i_int = 3, b_bool = 3, f_float = 4.20389539e-45, psz_string = 0x3 <Error reading address 0x3: Bad address>, p_address = 0x3, p_object = 0x3, p_list = 0x3, i_time = 3, var = {psz_name = 0x3 <Error reading address 0x3: Bad address>, i_object_id = 0}, padding = {a = 3 '\003', b = 0 '\0', c = 0 '\0', d = 0 '\0', e = 0 '\0', f = 0 '\0', g = 0 '\0', h = 0 '\0'}}, newval=
        {i_int = 5, b_bool = 5, f_float = 7.00649232e-45, psz_string = 0x5 <Error reading address 0x5: Bad address>, p_address = 0x5, p_object = 0x5, p_list = 0x5, i_time = 5, var = {psz_name = 0x5 <Error reading address 0x5: Bad address>, i_object_id = 0}, padding = {a = 5 '\005', b = 0 '\0', c = 0 '\0', d = 0 '\0', e = 0 '\0', f = 0 '\0', g = 0 '\0', h = 0 '\0'}}, p_data=0x2867ad40)
    at vlc_objects.h:166
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x28131c53 in __var_Set (p_this=0x28657c10, psz_name=0x2814cdca "state", 
    val=Variable "val" is not available.
) at ../../trunk/src/misc/variables.c:798
[#6](https://code.videolan.org/videolan/vlc/-/issues/6)  0x280c9604 in MainLoop (p_input=0x28657c10) at vlc_variables.h:205
[#7](https://code.videolan.org/videolan/vlc/-/issues/7)  0x280cae99 in Run (p_input=0x28657c10) at ../../trunk/src/input/input.c:507
[#8](https://code.videolan.org/videolan/vlc/-/issues/8)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#9](https://code.videolan.org/videolan/vlc/-/issues/9)  0xbf0f5fec in ?? ()

Thread 2 (Thread 0x28602900 (LWP 100163)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x2835459b in _umtx_op () from /lib/libc.so.7
---Type <return> to continue, or q <return> to quit---
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830b9b8 in pthread_cleanup_push () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x2830a1be in pthread_cond_init () from /lib/libthr.so.3
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x28112d84 in block_FifoGet (p_fifo=0x2930d610) at vlc_threads_funcs.h:501
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x280b5d82 in DecoderThread (p_dec=0x29701430)
    at ../../trunk/src/input/decoder.c:582
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#6](https://code.videolan.org/videolan/vlc/-/issues/6)  0xbf2f7fec in ?? ()

Thread 1 (Thread 0x28602600 (LWP 100164)):
[#0](https://code.videolan.org/videolan/vlc/-/issues/0)  0x283c910f in nanosleep () from /lib/libc.so.7
[#1](https://code.videolan.org/videolan/vlc/-/issues/1)  0x2830288b in nanosleep () from /lib/libthr.so.3
[#2](https://code.videolan.org/videolan/vlc/-/issues/2)  0x28111f3c in msleep (delay=5804) at ../../trunk/src/misc/mtime.c:342
[#3](https://code.videolan.org/videolan/vlc/-/issues/3)  0x285774e2 in OSSThread (p_aout=0x28701400)
    at ../../../trunk/modules/audio_output/oss.c:627
[#4](https://code.videolan.org/videolan/vlc/-/issues/4)  0x28303a7f in pthread_getprio () from /lib/libthr.so.3
[#5](https://code.videolan.org/videolan/vlc/-/issues/5)  0xbeef3fec in ?? ()
(gdb) 

removed Status::fixed label

reopened

Apparently, PlayingChange waits for the audioscrobbler thread, which is waiting for its "waitpipe" (read() inside vlc_object_wait()). Unlocking object_lock around the read() should work-around the problem. I'll try to make a proper fix later.

(In [24657]) Only use waitpipe for _kill, rather than _signal, which is what people expect (You really don't usually want your net_Read/net_Write to interrupted). In the process, fix a deadlock in vlc_cond_wait() when waitpipe is used - fixes #1448 (closed)

added Status::fixed label

closed