https://bugs.llvm.org/show_bug.cgi?id=36162
Bug ID: 36162
Summary: Unlocking equivalent to scoped_lockable for Thread
Safety Analysis
Product: clang
Version: trunk
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: Static Analyzer
Assignee: dcough...@apple.com
Reporter: cos...@gmail.com
CC: llvm-bugs@lists.llvm.org
I'm trying to add thread safety annotations [1] to Chromium.
We have AutoLock type [2], which works like MutexLocker in the Clang
documentation [1], so it can be annotated with __attribute__((scoped_locker))
(SCOPED_CAPABILITY in the Clang documentation). Unfortunately, we also have an
AutoUnlock type [3] that's used to safely drop a lock while performing a block
of work.
Examples of usage:
https://cs.chromium.org/chromium/src/ipc/ipc_mojo_bootstrap.cc?q=AutoUnlock
https://cs.chromium.org/chromium/src/tools/gn/input_file_manager.cc?q=AutoUnlock
So, using thread safety annotations in Chromium is blocked on getting a
scoped_unlocker annotation that causes the type's constructor to remove the
lock from the set of held locks (used by the analyzer), and causes the type's
destructor to add the lock back to the set of held locks.
Shooting in the dark, I tried adding scoped_locker to AutoUnlock and annotating
the constructor with unlock_function and the destructor with
exclusive_lock_function, so this might be an alternative solution.
I will try to put together a patch for this, but I've never contributed to LLVM
before, and this isn't prioritized by my employer, so I'll probably be very
slow. Also, I won't be upset if someone else provides a patch before me.
[1] https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
[2] https://cs.chromium.org/chromium/src/base/synchronization/lock.h?q=AutoLock
[3]
https://cs.chromium.org/chromium/src/base/synchronization/lock.h?q=AutoUnlock
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