fix cond_race... was RE: src/winsup/cygwin ChangeLog thread.cc thread.h ...

Sun Sep 30 05:21:00 GMT 2001

 Robert Collins writes:
>
>----- Original Message -----
>From: "Norman Vine"
>
>> Robert Collins writes:
>>
>> >----- Original Message -----
>> >From: "Jason Tishler" <jason@tishler.net>
>> >>
>> >> On Fri, Sep 28, 2001 at 05:48:16PM +1000, Robert Collins wrote:
>> >> > Well this patch should make evreything good -  fixing the critical
>> >> > section induced race.
>> >>
>> >> At the risk of appearing dense...  Should this patch fix the pthreads
hang
>> >> trigger by Python's test_threadedtempfile regression test?
>> >
>> >I've checked in my completed code. I -cannot- tickle this bug via my
>> >test suite at all now. (I found that one of my test scripts was slightly
>> >buggy in that it made an incorrect assumption - it was passing when this
>> >bug was tickled - correcting that let me hit this bug nearly every time
>> >:]).
>> >
>> >So please, give it a go and see how it fares.
>>
>> This now causes a hard crash in any of the Python threading tests
>> with an attempt to read memory at 0x00000018 failure.
>>
>> Note I believe this started, for me at least, with the
>second piece of this  patch.
>> Also note that I could not tickle this bug before.
>
>Interesting. Well I can drop you an updated test case which I'm sure
>will tickle the older .dll. Also I found that backgrounding the window
>the test is running in took the chance of hitting the bug from "very
>likely" to "sure thing" - if you'll excuse the technical talk :].
>
>> Win2k sp2  Cygwin=ntsec   python src 2-1.1-2 from cygwin distribution
>>

See attached

-------------- next part --------------
D:\usr\src\python-2.1.1>d:/bin/gdb.exe -nw /usr/src/python-2.1.1/python.exe 1004

GNU gdb 5.0 (20010428-1)
Copyright 2001 Free Software Foundation, Inc.
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This GDB was configured as "i686-pc-cygwin"...
/usr/src/python-2.1.1/1004: No such file or directory.
Attaching to program `/usr/src/python-2.1.1/python.exe', process 1004

Program received signal SIGSEGV, Segmentation fault.

---Type <return> to continue, or q <return> to quit---q
Quit
(gdb) bt
#0  0x77f821e1 in _libkernel32_a_iname ()
#1  0x61062e0c in pthread_mutex::Lock (this=0x0)
    at /src/cygwin/src/winsup/cygwin/thread.cc:694
#2  0x6106452a in __pthread_cond_dowait (cond=0xa05e6fc, mutex=0xa05e700,
    waitlength=-1) at /src/cygwin/src/winsup/cygwin/thread.cc:1776
#3  0x61064640 in pthread_cond_wait (cond=0xa05e6fc, mutex=0xa05e700)
    at /src/cygwin/src/winsup/cygwin/thread.cc:1806
#4  0x61d928a5 in PyThread_acquire_lock (lock=0xa05e6f8, waitflag=1)
    at Python/thread_pthread.h:313
#5  0x61d721f6 in eval_code2 (co=0xa07ac48, globals=0xa088aa4, locals=0x0,
    args=0xa0b86cc, argcount=0, kws=0xa0b86cc, kwcount=0, defs=0xa0505e8,
    defcount=1, closure=0x0) at Python/ceval.c:721
#6  0x61d76405 in fast_function (func=0xa0800e4, pp_stack=0x22f8fc, n=0, na=0,
    nk=0) at Python/ceval.c:3022
#7  0x61d7485d in eval_code2 (co=0xa07b2e0, globals=0xa088aa4, locals=0x0,
    args=0xa0b63f0, argcount=1, kws=0x0, kwcount=0, defs=0xa080330,
    defcount=6, closure=0x0) at Python/ceval.c:1972
#8  0x61d76303 in call_eval_code2 (func=0xa0802ec, arg=0xa0b63e4, kw=0x0)
    at Python/ceval.c:2966
#9  0x61d75e42 in call_object (func=0xa0802ec, arg=0xa0b63e4, kw=0x0)
    at Python/ceval.c:2805
#10 0x61d761b9 in call_method (func=0xa0802ec, arg=0xa0150f4, kw=0x0)
    at Python/ceval.c:2923
#11 0x61d75e2e in call_object (func=0xa0b790c, arg=0xa0150f4, kw=0x0)
---Type <return> to continue, or q <return> to quit---
    at Python/ceval.c:2803
#12 0x61d75c8e in PyEval_CallObjectWithKeywords (func=0xa0b790c,
    arg=0xa0150f4, kw=0x0) at Python/ceval.c:2740
#13 0x61d48636 in PyInstance_New (klass=0xa09fadc, arg=0xa0150f4, kw=0x0)
    at Objects/classobject.c:489
#14 0x61d75e6a in call_object (func=0xa09fadc, arg=0xa0150f4, kw=0x0)
    at Python/ceval.c:2809
#15 0x61d766f0 in do_call (func=0xa09fadc, pp_stack=0x22fb8c, na=0, nk=0)
    at Python/ceval.c:3123
#16 0x61d74877 in eval_code2 (co=0xa086468, globals=0xa01544c, locals=0x0,
    args=0xa020f84, argcount=0, kws=0xa020f84, kwcount=0, defs=0x0,
    defcount=0, closure=0x0) at Python/ceval.c:1975
#17 0x61d76405 in fast_function (func=0xa09f45c, pp_stack=0x22fcbc, n=0, na=0,
    nk=0) at Python/ceval.c:3022
#18 0x61d7485d in eval_code2 (co=0xa07d258, globals=0xa01544c,
    locals=0xa01544c, args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0,
    defcount=0, closure=0x0) at Python/ceval.c:1972
#19 0x61d71480 in PyEval_EvalCode (co=0xa07d258, globals=0xa01544c,
    locals=0xa01544c) at Python/ceval.c:341
#20 0x61d8f639 in run_node (n=0xa05c868,
    filename=0x614d5164 "Lib/test/test_threadedtempfile.py",
    globals=0xa01544c, locals=0xa01544c, flags=0x22fe70)
    at Python/pythonrun.c:1045
#21 0x61d8f5ea in run_err_node (n=0xa05c868,
---Type <return> to continue, or q <return> to quit---
    filename=0x614d5164 "Lib/test/test_threadedtempfile.py",
    globals=0xa01544c, locals=0xa01544c, flags=0x22fe70)
    at Python/pythonrun.c:1032
#22 0x61d8f5ba in PyRun_FileExFlags (fp=0xa010374,
    filename=0x614d5164 "Lib/test/test_threadedtempfile.py", start=257,
    globals=0xa01544c, locals=0xa01544c, closeit=1, flags=0x22fe70)
    at Python/pythonrun.c:1023
#23 0x61d8e864 in PyRun_SimpleFileExFlags (fp=0xa010374,
    filename=0x614d5164 "Lib/test/test_threadedtempfile.py", closeit=1,
    flags=0x22fe70) at Python/pythonrun.c:665
#24 0x61d8e30c in PyRun_AnyFileExFlags (fp=0xa010374,
    filename=0x614d5164 "Lib/test/test_threadedtempfile.py", closeit=1,
    flags=0x22fe70) at Python/pythonrun.c:479
#25 0x61d94a68 in Py_Main (argc=2, argv=0x614d50f4) at Modules/main.c:320
#26 0x00401061 in main (argc=2, argv=0x614d50f4) at Modules/python.c:10
#27 0x61003f42 in dll_crt0_1 () at /src/cygwin/src/winsup/cygwin/dcrt0.cc:772
#28 0x61004171 in _dll_crt0 () at /src/cygwin/src/winsup/cygwin/dcrt0.cc:840
#29 0x610041b0 in dll_crt0 (uptr=0x0)
    at /src/cygwin/src/winsup/cygwin/dcrt0.cc:852
#30 0x004010bf in cygwin_crt0 ()
    at /src/cygwin/src/winsup/cygwin/lib/cygwin_crt0.c:33
(gdb) select 1
Current language:  auto; currently c++
(gdb) info locals
this = (pthread_mutex *) 0x4
(gdb) up
#2  0x6106452a in __pthread_cond_dowait (cond=0xa05e6fc, mutex=0xa05e700,
    waitlength=-1) at /src/cygwin/src/winsup/cygwin/thread.cc:1776
1776      (*cond)->mutex->Lock ();
(gdb) info locals
cond = (pthread_cond_t *) 0xa05e6fc
mutex = (pthread_mutex_t *) 0xa05e700
waitlength = 4
rv = 0
(gdb) up
#3  0x61064640 in pthread_cond_wait (cond=0xa05e6fc, mutex=0xa05e700)
    at /src/cygwin/src/winsup/cygwin/thread.cc:1806
1806      return __pthread_cond_dowait (cond, mutex, INFINITE);
(gdb) info locals
cond = (pthread_cond_t *) 0x4
mutex = (pthread_mutex_t *) 0x4
(gdb) up
#4  0x61d928a5 in PyThread_acquire_lock (lock=0xa05e6f8, waitflag=1)
    at Python/thread_pthread.h:313
313                             status = pthread_cond_wait(&thelock->lock_releas
ed,
Current language:  auto; currently c
(gdb) info locals
lock = 0xa05e6f8
success = 168158976
status = 4
error = 0
(gdb) up
#5  0x61d721f6 in eval_code2 (co=0xa07ac48, globals=0xa088aa4, locals=0x0,
    args=0xa0b86cc, argcount=0, kws=0xa0b86cc, kwcount=0, defs=0xa0505e8,
    defcount=1, closure=0x0) at Python/ceval.c:721
721                                     PyThread_acquire_lock(interpreter_lock,
1);
(gdb) info locals
globals = (PyObject *) 0x4
locals = (PyObject *) 0x4
args = (PyObject **) 0xa07a358
stack_pointer = (PyObject **) 0xa0b6050
next_instr = (unsigned char *) 0xa07ac0d "t"
opcode = 124
oparg = 0
why = WHY_NOT
err = 0
x = (PyObject *) 0xa07a358
v = (PyObject *) 0xa010588
w = (PyObject *) 0xa07ac20
u = (PyObject *) 0xffffffff
t = (PyObject *) 0xa07a358
stream = (PyObject *) 0x0
f = (PyFrameObject *) 0xa0b5f00
fastlocals = (PyObject **) 0xa0b6048
freevars = (PyObject **) 0xa0b604c
retval = (PyObject *) 0x0
tstate = (PyThreadState *) 0xa010588
first_instr = (unsigned char *) 0xa07abf4 "\1772\001\1773\001\1774\001t"
(gdb) up
#6  0x61d76405 in fast_function (func=0xa0800e4, pp_stack=0x22f8fc, n=0, na=0,
    nk=0) at Python/ceval.c:3022
3022            return eval_code2((PyCodeObject *)co, globals,
(gdb) info locals
func = (PyObject *) 0x4
pp_stack = (PyObject ***) 0x4
na = 4
nk = 0
co = (PyObject *) 0xa07ac48
globals = (PyObject *) 0xa088aa4
argdefs = (PyObject *) 0x4
closure = (PyObject *) 0x4
d = (PyObject **) 0xa0505e8
nd = 2147344384
(gdb) up
#7  0x61d7485d in eval_code2 (co=0xa07b2e0, globals=0xa088aa4, locals=0x0,
    args=0xa0b63f0, argcount=1, kws=0x0, kwcount=0, defs=0xa080330,
    defcount=6, closure=0x0) at Python/ceval.c:1972
1972                                        x = fast_function(func, &stack_point
er,
(gdb) info locals
na = 168331940
nk = 0
n = 0
pfunc = (PyObject **) 0xa0b86c8
func = (PyObject *) 0x0
globals = (PyObject *) 0x4
locals = (PyObject *) 0x4
args = (PyObject **) 0xa088aa4
stack_pointer = (PyObject **) 0xa0b86cc
next_instr = (unsigned char *) 0xa07ae22 "\203\001"
opcode = 131
oparg = 0
why = WHY_NOT
err = 0
x = (PyObject *) 0xa0800e4
v = (PyObject *) 0xa0505e8
w = (PyObject *) 0xa07b128
u = (PyObject *) 0x0
t = (PyObject *) 0xa088aa4
stream = (PyObject *) 0x0
f = (PyFrameObject *) 0xa0b8560
fastlocals = (PyObject **) 0xa0b86a8
freevars = (PyObject **) 0xa0b86c4
retval = (PyObject *) 0x0
---Type <return> to continue, or q <return> to quit---
tstate = (PyThreadState *) 0xa010588
first_instr = (unsigned char *) 0xa07adcc "\177C\001\177E\001t"
(gdb) up
#8  0x61d76303 in call_eval_code2 (func=0xa0802ec, arg=0xa0b63e4, kw=0x0)
    at Python/ceval.c:2966
2966            result = eval_code2(
(gdb) info locals
result = (PyObject *) 0x0
argdefs = (PyObject *) 0x4
d = (PyObject **) 0xa080330
k = (PyObject **) 0x0
nk = 4
nd = 6
(gdb)