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Fix memory load ordering bug #66952

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merged 4 commits into from
Mar 21, 2022
Merged

Fix memory load ordering bug #66952

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aa34c40
Fix memory load ordering bug
jkoritzinsky Mar 21, 2022
dba8d82
Update src/native/libs/System.Native/pal_dynamicload.c
jkoritzinsky Mar 21, 2022
1b66624
Add explicit cast to remove the volatile modifier.
jkoritzinsky Mar 21, 2022
b49087d
Re-order volatile qualifier to make sure it applies to the void*, not…
jkoritzinsky Mar 21, 2022
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13 changes: 9 additions & 4 deletions src/native/libs/System.Native/pal_dynamicload.c
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Original file line number Diff line number Diff line change
Expand Up @@ -57,13 +57,18 @@ void* SystemNative_GetDefaultSearchOrderPseudoHandle(void)
return (void*)RTLD_DEFAULT;
}
#else
static void* g_defaultSearchOrderPseudoHandle = NULL;
static void* volatile g_defaultSearchOrderPseudoHandle = NULL;
void* SystemNative_GetDefaultSearchOrderPseudoHandle(void)
{
if (g_defaultSearchOrderPseudoHandle == NULL)
// Read the value once from the volatile static to avoid reading from memory twice.
void* defaultSearchOrderPseudoHandle = (void*)g_defaultSearchOrderPseudoHandle;
if (defaultSearchOrderPseudoHandle == NULL)
{
g_defaultSearchOrderPseudoHandle = dlopen(NULL, RTLD_LAZY);
// Assign back to the static as well as the local here.
// We don't need to check for a race between two threads as the value returned by
// dlopen here will always be the same in a given environment.
g_defaultSearchOrderPseudoHandle = defaultSearchOrderPseudoHandle = dlopen(NULL, RTLD_LAZY);
}
return g_defaultSearchOrderPseudoHandle;
return defaultSearchOrderPseudoHandle;
}
#endif