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Posted to commits@harmony.apache.org by "Ilya Leviev (JIRA)" <ji...@apache.org> on 2007/05/21 15:12:16 UTC
[jira] Updated: (HARMONY-3923) [drlvm][thread] Race conditions at
"port_atomic.h":117 and "thread_native_thin_monitor.c":253
[ https://issues.apache.org/jira/browse/HARMONY-3923?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Ilya Leviev updated HARMONY-3923:
---------------------------------
Environment: win2003 (was: wim2003)
> [drlvm][thread] Race conditions at "port_atomic.h":117 and "thread_native_thin_monitor.c":253
> ---------------------------------------------------------------------------------------------
>
> Key: HARMONY-3923
> URL: https://issues.apache.org/jira/browse/HARMONY-3923
> Project: Harmony
> Issue Type: Bug
> Components: DRLVM
> Environment: win2003
> Reporter: Ilya Leviev
>
> TC report on thread unsafe access that result in race condition that occur during concurrent execution of apr_atomic_cas32 and hythread_thin_monitor_try_enter functions.
> Write -> Read data-race
> Memory read at "thread_native_thin_monitor.c":253 conflicts with a prior memory write at "port_atomic.h":117
> Stack Trace:
> Context
> Function void vm_execute_java_method_array(struct _jmethodID *,union jvalue *,union jvalue *) "ini.cpp":60
> Function ExecuteMethod "em_intf.cpp":43
> Function void DrlEMImpl::executeMethod(struct _jmethodID *,union jvalue *,union jvalue *) "drlemimpl.cpp":509
> Function void JIT_execute_method_default(void *,struct _jmethodID *,union jvalue *,union jvalue *) "ini_ia32.cpp":199
> Function vm_invoke_native_array_stub "ini_ia32.cpp":76
> Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> Function m2n_free_local_handles "m2n_ia32.cpp":268
> Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> Function m2n_free_local_handles "m2n_ia32.cpp":268
> Function hythread_thin_monitor_try_enter "thread_native_thin_monitor.c":233
> 1st Access - Write
> Function void DrlEMImpl::executeMethod(struct _jmethodID *,union jvalue *,union jvalue *) "drlemimpl.cpp":509
> Function void JIT_execute_method_default(void *,struct _jmethodID *,union jvalue *,union jvalue *) "ini_ia32.cpp":199
> Function vm_invoke_native_array_stub "ini_ia32.cpp":76
> Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> Function m2n_free_local_handles "m2n_ia32.cpp":268
> Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> Function m2n_free_local_handles "m2n_ia32.cpp":268
> Function hythread_thin_monitor_try_enter "thread_native_thin_monitor.c":333
> Function hythread_thin_monitor_try_enter "thread_native_thin_monitor.c":286
> "285" "" " if (0 != port_atomic_cas16 (((volatile apr_uint16_t*) lockword_ptr)+1, "
> "286" "" " (apr_uint16_t) this_id, 0)) {"
> "287" "" " "
> Function port_atomic_cas16 "port_atomic.h":117
> "112" "" " INLINE uint16 port_atomic_cas16(volatile uint16 * data , uint16 value, uint16 comp) {"
> "113" "" " __asm {"
> "114" "" " mov ax, comp"
> "115" "" " mov dx, value"
> "116" "" " mov ecx, data"
> "117" "*" " lock cmpxchg [ecx], dx"
> "118" "" " mov comp, ax"
> "119" "" " }"
> "120" "" " return comp;"
> 2nd Access - Read
> Function void vm_execute_java_method_array(struct _jmethodID *,union jvalue *,union jvalue *) "ini.cpp":60
> Function ExecuteMethod "em_intf.cpp":43
> Function void DrlEMImpl::executeMethod(struct _jmethodID *,union jvalue *,union jvalue *) "drlemimpl.cpp":509
> Function void JIT_execute_method_default(void *,struct _jmethodID *,union jvalue *,union jvalue *) "ini_ia32.cpp":199
> Function vm_invoke_native_array_stub "ini_ia32.cpp":76
> Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> Function m2n_free_local_handles "m2n_ia32.cpp":268
> Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> Function m2n_free_local_handles "m2n_ia32.cpp":268
> Function hythread_thin_monitor_try_enter "thread_native_thin_monitor.c":253
> "253" "*" " lockword = *lockword_ptr; "
> "254" "" " lock_id = THREAD_ID(lockword);"
> "255" "" " //TRACE((""try lock %x %d"", this_id, RECURSION(lockword)));"
> See also Source View screenshots.
> Notes on Write->Read race condition.
> ------------------------------------
> Write->Read data races occur when one thread writes a shared memory location (address) while another thread concurrently reads the same memory location.
> The shared memory location may be referred to by (variable) name, pointer, or even a function such as memcpy().
> The following example uses a variable name:
> 1st access by first thread
> S1: sharedX = privateA
> 2nd access by second thread
> S2: privateB = sharedX
> If sharedX is a variable visible to all threads and privateA and privateB are local variables visible only to the thread where each was declared,
> concurrent execution of the above statements by multiple threads results in a "race" on the value to be read from sharedX.
> Since the order of execution among threads is unpredictable, it is unknown which value will be available in sharedX to be stored into privateB.
> This results in non-deterministic software, or software prone to produce different results each time it is executed.
> _______________________________________________________________________________________________________________________
> If it not affect correctness of execution I will mark it by special API for prevention of further alarms on this race.
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