Title: [149136] trunk/Source/_javascript_Core
- Revision
- 149136
- Author
- [email protected]
- Date
- 2013-04-25 13:00:36 -0700 (Thu, 25 Apr 2013)
Log Message
Stack guards are too conservative
https://bugs.webkit.org/show_bug.cgi?id=115147
Reviewed by Geoffrey Garen.
Reduce the limits and simplify the decision making.
* interpreter/Interpreter.cpp:
(JSC::Interpreter::StackPolicy::StackPolicy):
Modified Paths
Diff
Modified: trunk/Source/_javascript_Core/ChangeLog (149135 => 149136)
--- trunk/Source/_javascript_Core/ChangeLog 2013-04-25 19:56:58 UTC (rev 149135)
+++ trunk/Source/_javascript_Core/ChangeLog 2013-04-25 20:00:36 UTC (rev 149136)
@@ -1,3 +1,15 @@
+2013-04-25 Oliver Hunt <[email protected]>
+
+ Stack guards are too conservative
+ https://bugs.webkit.org/show_bug.cgi?id=115147
+
+ Reviewed by Geoffrey Garen.
+
+ Reduce the limits and simplify the decision making.
+
+ * interpreter/Interpreter.cpp:
+ (JSC::Interpreter::StackPolicy::StackPolicy):
+
2013-04-25 Nick Diego Yamane <[email protected]>
JSC: Fix interpreter misbehavior in builds with JIT disabled
Modified: trunk/Source/_javascript_Core/interpreter/Interpreter.cpp (149135 => 149136)
--- trunk/Source/_javascript_Core/interpreter/Interpreter.cpp 2013-04-25 19:56:58 UTC (rev 149135)
+++ trunk/Source/_javascript_Core/interpreter/Interpreter.cpp 2013-04-25 20:00:36 UTC (rev 149136)
@@ -119,82 +119,20 @@
{
const size_t size = stack.size();
- const size_t DEFAULT_REQUIRED_STACK = 1024 * 1024;
- const size_t DEFAULT_MINIMUM_USEABLE_STACK = 128 * 1024;
- const size_t DEFAULT_ERROR_MODE_REQUIRED_STACK = 32 * 1024;
-
- // Here's the policy in a nutshell:
+ // We have two separate stack limits, one for regular JS execution, and one
+ // for when we're handling errors. We need the error stack to be smaller
+ // otherwise there would obviously not be any stack left to execute JS in when
+ // there's a stack overflow.
//
- // 1. If we have a large stack, let JS use as much stack as possible
- // but require that we have at least DEFAULT_REQUIRED_STACK capacity
- // remaining on the stack:
- //
- // stack grows this way -->
- // ---------------------------------------------------------
- // | ... | <-- DEFAULT_REQUIRED_STACK --> | ...
- // ---------------------------------------------------------
- // ^ ^
- // start current sp
- //
- // 2. In event that we're re-entering the interpreter to handle
- // exceptions (in error mode), we'll be a little more generous and
- // require less stack capacity for the interpreter to be re-entered.
- //
- // This is needed because we may have just detected an eminent stack
- // overflow based on the normally computed required stack capacity.
- // However, the normal required capacity far exceeds what is needed
- // for exception handling work. Hence, in error mode, we only require
- // DEFAULT_ERROR_MODE_REQUIRED_STACK capacity.
- //
- // stack grows this way -->
- // -----------------------------------------------------------------
- // | ... | <-- DEFAULT_ERROR_MODE_REQUIRED_STACK --> | ...
- // -----------------------------------------------------------------
- // ^ ^
- // start current sp
- //
- // This smaller required capacity also means that we won't re-trigger
- // a stack overflow for processing the exception caused by the original
- // StackOverflowError.
- //
- // 3. If the stack is not large enough, give JS at least a minimum
- // amount of useable stack:
- //
- // stack grows this way -->
- // --------------------------------------------------------------------
- // | <-- DEFAULT_MINIMUM_USEABLE_STACK --> | <-- requiredCapacity --> |
- // --------------------------------------------------------------------
- // ^ ^
- // start current sp
- //
- // The minimum useable capacity is DEFAULT_MINIMUM_USEABLE_STACK.
- // In this case, the requiredCapacity is whatever is left of the
- // total stack capacity after we have give JS its minimum stack
- // i.e. requiredCapacity can even be 0 if there's not enough stack.
+ // These sizes were derived from the stack usage of a number of sites when
+ // layout occurs when we've already consumed most of the C stack.
+ const size_t requiredStack = 64 * KB;
+ const size_t errorModeRequiredStack = 32 * KB;
+ size_t requiredCapacity = m_interpreter.m_errorHandlingModeReentry ? errorModeRequiredStack : requiredStack;
- // Policy 1: Normal mode: required = DEFAULT_REQUIRED_STACK.
- // Policy 2: Error mode: required = DEFAULT_ERROR_MODE_REQUIRED_STACK.
- size_t requiredCapacity = !m_interpreter.m_errorHandlingModeReentry ?
- DEFAULT_REQUIRED_STACK : DEFAULT_ERROR_MODE_REQUIRED_STACK;
-
- size_t useableStack = (requiredCapacity <= size) ?
- size - requiredCapacity : DEFAULT_MINIMUM_USEABLE_STACK;
-
- // Policy 3: Ensure the useable stack is not too small:
- if (useableStack < DEFAULT_MINIMUM_USEABLE_STACK)
- useableStack = DEFAULT_MINIMUM_USEABLE_STACK;
-
- // Sanity check: Make sure we do not use more space than the stack's
- // total capacity:
- if (useableStack > size)
- useableStack = size;
-
- // Re-compute the requiredCapacity based on the adjusted useable stack
- // size:
- requiredCapacity = size - useableStack;
- ASSERT(requiredCapacity < size);
-
+ RELEASE_ASSERT(size > requiredCapacity);
+
m_requiredCapacity = requiredCapacity;
}
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