Prevent inlining of *.runWith methods #18152
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babsingh
reviewed
Sep 15, 2023
0xdaryl
reviewed
Sep 15, 2023
| * relies on iterating the O-slots of these methods to find the most recent ScopedValue binding. | ||
| * The scoped value binding is the first argument in runWith, and if runWith is compiled, the | ||
| * O-slot walker would rely on iterating through the O-slots until an object that is an instance | ||
| * of jdk.incubator.concurrent.ScopedValue$Snapshot is found. If we were to allow inlining of |
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Should this be an incubator package name here? For JDK21 I imagine it isn't.
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It's not in incubator package in JDK21, so I fixed the comment.
runtime/compiler/env/j9method.cpp
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| @@ -3957,6 +3958,18 @@ void TR_ResolvedJ9Method::construct() | |||
| {TR::unknownMethod} | |||
| }; | |||
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| static X VirtualThreadMethods [] = | |||
| { | |||
| { TR::java_lang_VirtualThread_runWith, 7, "runWith", (int16_t)-1, "*"}, | |||
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Just curious about the whitespace here. I imagine it is for alignment, but since these are the only entries in these tables it is hard to see what they are being aligned with.
Thread.findScopedValueBindings implementation relies on iterating the O-slots of these methods to find the most recent ScopedValue binding. The scoped value binding is the first argument in runWith, and if runWith is compiled, the O-slot walker would rely on iterating through the O-slots until an object that is an instance of jdk.incubator.concurrent.ScopedValue$Snapshot is found. If we were to allow inlining of runWith, this slot walking mechanism would be unreliable, such as when there are more than one runWith calls in the same caller, and iterating through the O-slots and relying on instanceof checks could then yield the wrong bindings. Signed-off-by: Nazim Bhuiyan <nubhuiyan@ibm.com>
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Jenkins test sanity all jdk21 |
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Jenkins test sanity plinux jdk21 |
0xdaryl
approved these changes
Sep 18, 2023
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Thread.findScopedValueBindings implementation relies on iterating the O-slots of these methods to find the most recent ScopedValue binding. The scoped value binding is the first argument in runWith, and if runWith is compiled, the O-slot walker would rely on iterating through the O-slots until an object that is an instance of
jdk.incubator.concurrent.ScopedValue$Snapshot is found. If we were to allow inlining of runWith, this slot walking mechanism would be unreliable, such as when there are more than one runWith calls in the same caller, and iterating through the O-slots and relying on instanceof checks could then yield the wrong bindings.