1803322 - TestNativeNt broken in local build due to thread local storage pointer caching optimization

Status: RESOLVED FIXED

(Core :: mozglue, defect)

Description

[Yannis Juglaret [:yannis]]

On my local machine, TestNativeNt is broken:

$ ./obj-x86_64-pc-mingw32/dist/bin/TestNativeNt.exe
sTlsData#1 = 00000000
Segmentation fault

The reason seems to be the same as what's mentioned in the comment above SwapThreadLocalStoragePointer:

// Need a non-inline function to bypass compiler optimization that the thread
// local storage pointer is cached in a register before accessing a thread-local
// variable.

In my case, it seems that the new nullptr value for the thread-local storage pointer gets cached when we call sTlsData.set(~kTlsDataValue); inside MOZ_SEH_TRY, resulting in the next call to sTlsData.get() to dereference a null pointer. Replacing the set line by a call to a non-inlinable variant fixes the local test:

MOZ_NEVER_INLINE void setTlsData(unsigned x) { sTlsData.set(x); }

I believe that in all functions that change the thread-local storage pointer value using SwapThreadLocalStoragePointer, we should use non-inlinable variants of our thread-local storage helpers to make sure that it is never cached at any point of the test. That would be TestNativeNt and also TestSafeThreadLocal.

This may also fix bug 1784210?

Comment 1

[Yannis Juglaret [:yannis]]

Attachment: Bug 1803322 - Use non-inlinable thread-local helpers in TestNativeNt and TestSafeThreadLocal. r=glandium

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/9615b6d6fc0b
Use non-inlinable thread-local helpers in TestNativeNt and TestSafeThreadLocal. r=glandium

Comment 4

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/9615b6d6fc0b