On Tue, Jan 06, 2026 at 10:21PM +0900, Tetsuo Handa wrote:
> On 2025/12/20 0:39, Marco Elver wrote:
> > Introduce basic compatibility with cleanup.h infrastructure.
>
> Can Compiler-Based Context- and Locking-Analysis work with conditional guards
> (unlock only if lock succeeded) ?
>
> I consider that replacing mutex_lock() with mutex_lock_killable() helps
> reducing
> frequency of hung tasks under heavy load where many processes are preempted
> waiting
> for the same mutex to become available (e.g.
> https://syzkaller.appspot.com/bug?extid=8f41dccfb6c03cc36fd6 ).
>
> But e.g. commit f49573f2f53e ("tty: use lock guard()s in tty_io") already
> replaced
> plain mutex_lock()/mutex_unlock() with plain guard(mutex). If I propose a
> patch for
> replacing mutex_lock() with mutex_lock_killable(), can I use conditional
> guards?
> (Would be yes if Compiler-Based Context- and Locking-Analysis can work, would
> be no
> if Compiler-Based Context- and Locking-Analysis cannot work) ?
It works for cond guards, so yes. But, only if support for
mutex_lock_killable() is added. At the moment mutex.h only has:
...
DEFINE_LOCK_GUARD_1(mutex, struct mutex, mutex_lock(_T->lock),
mutex_unlock(_T->lock))
DEFINE_LOCK_GUARD_1_COND(mutex, _try, mutex_trylock(_T->lock))
DEFINE_LOCK_GUARD_1_COND(mutex, _intr,
mutex_lock_interruptible(_T->lock), _RET == 0)
DECLARE_LOCK_GUARD_1_ATTRS(mutex, __acquires(_T),
__releases(*(struct mutex **)_T))
#define class_mutex_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(mutex, _T)
DECLARE_LOCK_GUARD_1_ATTRS(mutex_try, __acquires(_T),
__releases(*(struct mutex **)_T))
#define class_mutex_try_constructor(_T)
WITH_LOCK_GUARD_1_ATTRS(mutex_try, _T)
DECLARE_LOCK_GUARD_1_ATTRS(mutex_intr, __acquires(_T),
__releases(*(struct mutex **)_T))
#define class_mutex_intr_constructor(_T)
WITH_LOCK_GUARD_1_ATTRS(mutex_intr, _T)
...
And we also have a test in lib/test_context-analysis.c checking it
actually works:
...
scoped_cond_guard(mutex_try, return, &d->mtx) {
d->counter++;
}
scoped_cond_guard(mutex_intr, return, &d->mtx) {
d->counter++;
}
...
What's missing is a variant for mutex_lock_killable(), but that should
be similar to the mutex_lock_interruptible() variant.
