STINNER Victor <vstin...@python.org> added the comment:
When the test hangs, a background Python process starts to use 100% of my CPU.
This process is stuck in _thread.start_new_thread(). I opened the process in
gdb.
(gdb) thread 1
[Switching to thread 1 (Thread 0x7fece33615c0 (LWP 132301))]
#0 __interceptor_pthread_create (thread=thread@entry=0x7ffe79cd6190,
attr=attr@entry=0x7ffe79cd61b0, start_routine=start_routine@entry=0x6fed30
<pythread_wrapper>, arg=arg@entry=0x60200019aed0)
at ../../../../libsanitizer/asan/asan_interceptors.cpp:245
245 while (atomic_load(¶m.is_registered, memory_order_acquire) == 0)
(gdb) where
#0 __interceptor_pthread_create (thread=thread@entry=0x7ffe79cd6190,
attr=attr@entry=0x7ffe79cd61b0, start_routine=start_routine@entry=0x6fed30
<pythread_wrapper>, arg=arg@entry=0x60200019aed0)
at ../../../../libsanitizer/asan/asan_interceptors.cpp:245
#1 0x00000000006ff242 in PyThread_start_new_thread (func=func@entry=0x7f45d0
<thread_run>, arg=arg@entry=0x604000e83c50) at Python/thread_pthread.h:287
(...)
(gdb) thread 2
[Switching to thread 2 (Thread 0x7fecd151c640 (LWP 132302))]
#0 __sanitizer::atomic_exchange<__sanitizer::atomic_uint32_t>
(mo=__sanitizer::memory_order_acquire, v=2, a=0x640000001b00) at
../../../../libsanitizer/sanitizer_common/sanitizer_atomic_clang.h:62
62 inline typename T::Type atomic_exchange(volatile T *a,
(gdb) where
#0 __sanitizer::atomic_exchange<__sanitizer::atomic_uint32_t>
(mo=__sanitizer::memory_order_acquire, v=2, a=0x640000001b00) at
../../../../libsanitizer/sanitizer_common/sanitizer_atomic_clang.h:62
#1 __sanitizer::BlockingMutex::Lock (this=this@entry=0x640000001b00) at
../../../../libsanitizer/sanitizer_common/sanitizer_linux.cpp:649
#2 0x00007fece3914e15 in
__sanitizer::GenericScopedLock<__sanitizer::BlockingMutex>::GenericScopedLock
(mu=0x640000001b00, this=<synthetic pointer>) at
../../../../libsanitizer/sanitizer_common/sanitizer_mutex.h:183
#3
__sanitizer::SizeClassAllocator64<__asan::AP64<__sanitizer::LocalAddressSpaceView>
>::GetFromAllocator (this=this@entry=0x7fece3a13f00 <__asan::instance>,
stat=stat@entry=0x7feccfb46c40, class_id=class_id@entry=36,
chunks=chunks@entry=0x7feccfb42330, n_chunks=n_chunks@entry=8) at
../../../../libsanitizer/sanitizer_common/sanitizer_allocator_primary64.h:146
#4 0x00007fece3914f41 in
__sanitizer::SizeClassAllocator64LocalCache<__sanitizer::SizeClassAllocator64<__asan::AP64<__sanitizer::LocalAddressSpaceView>
> >::Refill (this=this@entry=0x7feccfb390e0, c=c@entry=0x7feccfb42320,
allocator=allocator@entry=0x7fece3a13f00 <__asan::instance>,
class_id=class_id@entry=36) at
../../../../libsanitizer/sanitizer_common/sanitizer_allocator_local_cache.h:102
#5 0x00007fece3915209 in
__sanitizer::SizeClassAllocator64LocalCache<__sanitizer::SizeClassAllocator64<__asan::AP64<__sanitizer::LocalAddressSpaceView>
> >::Allocate (class_id=36, allocator=0x7fece3a13f00 <__asan::instance>,
this=0x7feccfb390e0) at
../../../../libsanitizer/sanitizer_common/sanitizer_allocator_local_cache.h:38
#6
__sanitizer::CombinedAllocator<__sanitizer::SizeClassAllocator64<__asan::AP64<__sanitizer::LocalAddressSpaceView>
>, __sanitizer::LargeMmapAllocatorPtrArrayDynamic>::Allocate
(this=this@entry=0x7fece3a13f00 <__asan::instance>,
cache=0x7feccfb390e0, size=<optimized out>, size@entry=8192,
alignment=alignment@entry=1) at
../../../../libsanitizer/sanitizer_common/sanitizer_allocator_combined.h:69
#7 0x00007fece39118f6 in __asan::QuarantineCallback::Allocate (size=8192,
this=<synthetic pointer>) at
../../../../libsanitizer/asan/asan_allocator.cpp:869
#8 __sanitizer::QuarantineCache<__asan::QuarantineCallback>::Enqueue (size=32,
ptr=0x6030005477d0, cb=..., this=0x7feccfb39060) at
../../../../libsanitizer/sanitizer_common/sanitizer_quarantine.h:223
#9 __sanitizer::Quarantine<__asan::QuarantineCallback, __asan::AsanChunk>::Put
(size=32, ptr=0x6030005477d0, cb=..., c=0x7feccfb39060, this=<optimized out>)
at ../../../../libsanitizer/sanitizer_common/sanitizer_quarantine.h:105
#10 __asan::Allocator::QuarantineChunk (this=this@entry=0x7fece3a13f00
<__asan::instance>, m=m@entry=0x6030005477d0, stack=stack@entry=0x7fecd151b360,
ptr=0x6030005477e0) at ../../../../libsanitizer/asan/asan_allocator.cpp:666
#11 0x00007fece3911ba5 in __asan::Allocator::Deallocate
(alloc_type=__asan::FROM_MALLOC, stack=0x7fecd151b360, delete_alignment=0,
delete_size=0, ptr=0x6030005477e0, this=0x7fece3a13f00 <__asan::instance>)
at ../../../../libsanitizer/asan/asan_allocator.cpp:714
#12 0x00007fece3997618 in __interceptor_free (ptr=0x6030005477e0) at
../../../../libsanitizer/asan/asan_malloc_linux.cpp:128
#13 0x00007fece362f7a4 in pthread_getattr_np@GLIBC_2.2.5 () from
/lib64/libc.so.6
#14 0x00007fece39b142e in __sanitizer::GetThreadStackTopAndBottom
(at_initialization=at_initialization@entry=false,
stack_top=stack_top@entry=0x7fecd151bd10,
stack_bottom=stack_bottom@entry=0x7fecd151bd18)
at ../../../../libsanitizer/sanitizer_common/sanitizer_linux_libcdep.cpp:143
#15 0x00007fece39b1778 in __sanitizer::GetThreadStackAndTls (main=<optimized
out>, stk_addr=stk_addr@entry=0x7feccfb39020,
stk_size=stk_size@entry=0x7fecd151bd68, tls_addr=tls_addr@entry=0x7feccfb39040,
tls_size=tls_size@entry=0x7fecd151bd60) at
../../../../libsanitizer/sanitizer_common/sanitizer_linux_libcdep.cpp:543
#16 0x00007fece39a3c93 in __asan::AsanThread::SetThreadStackAndTls
(this=this@entry=0x7feccfb39000, options=<optimized out>) at
../../../../libsanitizer/asan/asan_thread.h:81
#17 0x00007fece39a3fd6 in __asan::AsanThread::Init
(this=this@entry=0x7feccfb39000, options=options@entry=0x0) at
../../../../libsanitizer/asan/asan_thread.cpp:226
#18 0x00007fece39a446e in __asan::AsanThread::ThreadStart (this=0x7feccfb39000,
os_id=132302, signal_thread_is_registered=0x7ffe79cd58f8) at
../../../../libsanitizer/asan/asan_thread.cpp:258
#19 0x00007fece3781299 in start_thread () from /lib64/libpthread.so.0
#20 0x00007fece36a9353 in clone () from /lib64/libc.so.6
The thread 1 is stuck at the loop at the end of pthread_create(), line 245 an
246: wait until ¶m.is_registered == 0.
210 INTERCEPTOR(int, pthread_create, void *thread,
211 void *attr, void *(*start_routine)(void*), void *arg) {
212 EnsureMainThreadIDIsCorrect();
213 // Strict init-order checking is thread-hostile.
214 if (flags()->strict_init_order)
215 StopInitOrderChecking();
216 GET_STACK_TRACE_THREAD;
217 int detached = 0;
218 if (attr)
219 REAL(pthread_attr_getdetachstate)(attr, &detached);
220 ThreadStartParam param;
221 atomic_store(¶m.t, 0, memory_order_relaxed);
222 atomic_store(¶m.is_registered, 0, memory_order_relaxed);
223 int result;
224 {
225 // Ignore all allocations made by pthread_create: thread stack/TLS
may be
226 // stored by pthread for future reuse even after thread
destruction, and
227 // the linked list it's stored in doesn't even hold valid pointers
to the
228 // objects, the latter are calculated by obscure pointer arithmetic.
229 #if CAN_SANITIZE_LEAKS
230 __lsan::ScopedInterceptorDisabler disabler;
231 #endif
232 result = REAL(pthread_create)(thread, attr, asan_thread_start,
¶m);
233 }
234 if (result == 0) {
235 u32 current_tid = GetCurrentTidOrInvalid();
236 AsanThread *t =
237 AsanThread::Create(start_routine, arg, current_tid, &stack,
detached);
238 atomic_store(¶m.t, reinterpret_cast<uptr>(t),
memory_order_release);
239 // Wait until the AsanThread object is initialized and the
ThreadRegistry
240 // entry is in "started" state. One reason for this is that after
this
241 // interceptor exits, the child thread's stack may be the only
thing holding
242 // the |arg| pointer. This may cause LSan to report a leak if leak
checking
243 // happens at a point when the interceptor has already exited, but
the stack
244 // range for the child thread is not yet known.
245 while (atomic_load(¶m.is_registered, memory_order_acquire) == 0)
246 internal_sched_yield();
247 }
248 return result;
249 }
The thread 2 seems to be stuck in a syscall done by
__sanitizer::atomic_exchange<__sanitizer::atomic_uint32_t>, called by
__sanitizer::BlockingMutex::Lock:
(gdb) disassemble
Dump of assembler code for function _ZN11__sanitizer13BlockingMutex4LockEv:
0x00007fece39af850 <+0>: endbr64
0x00007fece39af854 <+4>: push r12
0x00007fece39af856 <+6>: push rbp
0x00007fece39af857 <+7>: push rbx
0x00007fece39af858 <+8>: mov rcx,QWORD PTR [rdi+0x50]
0x00007fece39af85c <+12>: test rcx,rcx
0x00007fece39af85f <+15>: jne 0x7fece39af8a8
<_ZN11__sanitizer13BlockingMutex4LockEv+88>
0x00007fece39af861 <+17>: mov eax,0x1
0x00007fece39af866 <+22>: xchg DWORD PTR [rdi],eax
0x00007fece39af868 <+24>: test eax,eax
0x00007fece39af86a <+26>: je 0x7fece39af89e
<_ZN11__sanitizer13BlockingMutex4LockEv+78>
0x00007fece39af86c <+28>: mov ebp,0x2
0x00007fece39af871 <+33>: mov r12d,0xca
0x00007fece39af877 <+39>: mov esi,0x80
0x00007fece39af87c <+44>: xor ebx,ebx
0x00007fece39af87e <+46>: mov edx,0x2
0x00007fece39af883 <+51>: jmp 0x7fece39af896
<_ZN11__sanitizer13BlockingMutex4LockEv+70>
0x00007fece39af885 <+53>: nop DWORD PTR [rax]
0x00007fece39af888 <+56>: mov rax,r12
0x00007fece39af88b <+59>: mov r10,rbx
0x00007fece39af88e <+62>: mov r8,rbx
0x00007fece39af891 <+65>: mov r9,rbx
0x00007fece39af894 <+68>: syscall
=> 0x00007fece39af896 <+70>: mov eax,ebp
0x00007fece39af898 <+72>: xchg DWORD PTR [rdi],eax
0x00007fece39af89a <+74>: test eax,eax
0x00007fece39af89c <+76>: jne 0x7fece39af888
<_ZN11__sanitizer13BlockingMutex4LockEv+56>
0x00007fece39af89e <+78>: pop rbx
0x00007fece39af89f <+79>: pop rbp
0x00007fece39af8a0 <+80>: pop r12
0x00007fece39af8a2 <+82>: ret
0x00007fece39af8a3 <+83>: nop DWORD PTR [rax+rax*1+0x0]
0x00007fece39af8a8 <+88>: xor r8d,r8d
0x00007fece39af8ab <+91>: lea rdx,[rip+0x37d7c] # 0x7fece39e762e
0x00007fece39af8b2 <+98>: mov esi,0x285
0x00007fece39af8b7 <+103>: lea rdi,[rip+0x37dfa] # 0x7fece39e76b8
0x00007fece39af8be <+110>: call 0x7fece39be990
<_ZN11__sanitizer11CheckFailedEPKciS1_yy>
End of assembler dump.
----------
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue45200>
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