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use a volatile pointer to call slp_switch #183
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akruis
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Nov 19, 2018
Prevent inlining slp_switch() more reliably. C standard guarantees to read the value of a volatile variable from memory on each access. Therefore the compiler does not know the called function and can't inline.
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akruis
pushed a commit
that referenced
this issue
Dec 25, 2018
Prevent inlining slp_switch() more reliably. C standard guarantees to read the value of a volatile variable from memory on each access. Therefore the compiler does not know the called function and can't inline. (cherry picked from commit 78f6b66)
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If the internal stack transfer function
slp_switch()is implemented using gcc/clang inline assembly, the inline assembly depends on the register allocation rules defined in the ABI-specification of the respective platform. Now if compiler inlines the function, the register allocation rules no longer apply and the behaviour is undefined.Experiments show that the only reliable way to prevent inlining is to call
slp_switch()using a volatile pointer. Here is the patch.This has the additional advantage that
slp_switch()now can be declared static, which reduces namespace pollution.The text was updated successfully, but these errors were encountered: