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Date: Tue, 29 May 2007 00:36:15 -0700 (PDT)
From: "Ilya Leviev (JIRA)" <jira@apache.org>
To: commits@harmony.apache.org
Subject: [jira] Updated: (HARMONY-3913) [drlvm][tc][thread] Race conditions
 at "thread_native_thin_monitor.c":78 and "thread_java_monitors.c":135
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     [ https://issues.apache.org/jira/browse/HARMONY-3913?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ilya Leviev updated HARMONY-3913:
---------------------------------

    Summary: [drlvm][tc][thread] Race conditions at "thread_native_thin_monitor.c":78 and "thread_java_monitors.c":135  (was: [drlvm][thread] Race conditions at "thread_native_thin_monitor.c":78 and "thread_java_monitors.c":135)

> [drlvm][tc][thread] Race conditions at "thread_native_thin_monitor.c":78 and "thread_java_monitors.c":135
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: HARMONY-3913
>                 URL: https://issues.apache.org/jira/browse/HARMONY-3913
>             Project: Harmony
>          Issue Type: Bug
>          Components: DRLVM
>         Environment: win2003
>            Reporter: Ilya Leviev
>         Attachments: SourceViewScreenshot-1.jpg
>
>
> TC report on thread unsafe access that result in race condition that occur during concurrent execution of set_fat_lock_id and unreserve_lock functions.
> Write -> Read data-race
> Memory read at "thread_native_thin_monitor.c":135 conflicts with a prior memory write at "thread_native_thin_monitor.c":78
> 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 hythread_thin_monitor_exit "thread_native_thin_monitor.c":416
> 	Function hythread_thin_monitor_try_enter "thread_native_thin_monitor.c":341
> 	Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> 	Function jthread_monitor_enter "thread_java_monitors.c":88
> 	Function unreserve_lock "thread_native_thin_monitor.c":134
> 1st Access
> 	Function vm_get_gc_thread_local "c_interface.cpp":2334
> 	Function m2n_free_local_handles "m2n_ia32.cpp":268
> 	Function hythread_self "hythread.h":465
> 	Function hythread_thin_monitor_exit "thread_native_thin_monitor.c":416
> 	Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> 	Function hythread_suspend_enable "hythread_ext.h":370
> 	Function Java_java_lang_VMThreadManager_wait "java_lang_vmthreadmanager.cpp":202
> 	Function jthread_monitor_timed_wait "thread_java_monitors.c":308
> 	Function inflate_lock "thread_native_thin_monitor.c":600
> 	Function set_fat_lock_id "thread_native_thin_monitor.c":78
> "76"	""	"     lockword&=0x7FF;"
> "77"	""	"     lockword|=(monitor_id << 11) | 0x80000000;"
> "78"	"*"	"     *lockword_ptr=lockword;"
> "79"	""	"     apr_memory_rw_barrier();"
> "80"	""	" }"
> 2nd Access
> 	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 hythread_thin_monitor_exit "thread_native_thin_monitor.c":416
> 	Function hythread_thin_monitor_try_enter "thread_native_thin_monitor.c":341
> 	Function class VM_thread * get_thread_ptr_stub(void) "thread_manager.cpp":138
> 	Function jthread_monitor_enter "thread_java_monitors.c":88
> 	Function unreserve_lock "thread_native_thin_monitor.c":135
> "134"	""	" IDATA unreserve_lock(hythread_thin_monitor_t *lockword_ptr) {"
> "135"	"*"	"     I_32 lockword = *lockword_ptr;"
> "136"	""	"     I_32 lockword_new;"
> "137"	""	"     uint16 lock_id;"
> See also Source View screenshot.
> 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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