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Date: Fri, 18 May 2007 08:38:17 -0700 (PDT)
From: "Ilya Leviev (JIRA)" <jira@apache.org>
To: commits@harmony.apache.org
Subject: [jira] Created: (HARMONY-3914) [drlvm][thread] Race conditions at
 "thread_native_basic.c":(480,275)
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[drlvm][thread] Race conditions at "thread_native_basic.c":(480,275)
--------------------------------------------------------------------

                 Key: HARMONY-3914
                 URL: https://issues.apache.org/jira/browse/HARMONY-3914
             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 hythread_get_thread and hythread_detach functions.


Read -> Write data-race	
Memory write at "thread_native_basic.c":275 conflicts with a prior memory read at "thread_native_basic.c":480


Stack Trace: 


Context
	Function jthread_create "thread_java_basic.c":63
	Function jthread_create_with_function "thread_java_basic.c":179
	Function hythread_create "thread_native_basic.c":165
	Function hythread_create_with_group "thread_native_basic.c":136
	Function os_thread_create "os_thread.c":37
	Function _beginthreadex "threadex.c":145
	Function EntryPoint "dllcrt0.c":323
	Function threadstartex "threadex.c":241
	Function thread_start_proc "thread_native_basic.c":720
	Function hythread_detach "thread_native_basic.c":259


1st Access
	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":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":151
	Function hythread_get_thread "thread_native_basic.c":480


"479"	""	" hythread_t VMCALL hythread_get_thread(IDATA id) {"
"480"	"*"	"     return fast_thread_array[id];"
"481"	""	" }"


2nd Access
	Function jthread_create "thread_java_basic.c":63
	Function jthread_create_with_function "thread_java_basic.c":179
	Function hythread_create "thread_native_basic.c":165
	Function hythread_create_with_group "thread_native_basic.c":136
	Function os_thread_create "os_thread.c":37
	Function _beginthreadex "threadex.c":145
	Function EntryPoint "dllcrt0.c":323
	Function threadstartex "threadex.c":241
	Function thread_start_proc "thread_native_basic.c":720
	Function hythread_detach "thread_native_basic.c":275

"274"	""	"         thread_set_self(NULL);"
"275"	"*"	"         fast_thread_array[thread->thread_id] = NULL;"
"276"	""	"         "


See also Source View screenshot.


Notes on Read->write race condition.
------------------------------------

Read->write data races occur when one thread reads a shared memory location (address) while another thread concurrently writes 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: privateA = sharedX 

2nd access by second thread

S2: sharedX = privateB 

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 what value will be read from sharedX and written into privateA.
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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