c21f11d182
In mutex_init() lockdep identifies a lock by defining a special static
key for each lock class. However if we wrap the macro in a function,
like in drmm_mutex_init(), we end up generating:
int drmm_mutex_init(struct drm_device *dev, struct mutex *lock)
{
static struct lock_class_key __key;
__mutex_init((lock), "lock", &__key);
....
}
The static __key here is what lockdep uses to identify the lock class,
however since this is just a normal function the key here will be
created once, where all callers then use the same key. In effect the
mutex->depmap.key will be the same pointer for different
drmm_mutex_init() callers. This then results in impossible lockdep
splats since lockdep thinks completely unrelated locks are the same lock
class.
To fix this turn drmm_mutex_init() into a macro such that it generates a
different "static struct lock_class_key __key" for each invocation,
which looks to be inline with what mutex_init() wants.
v2:
- Revamp the commit message with clearer explanation of the issue.
- Rather export __drmm_mutex_release() than static inline.
Reported-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reported-by: Sarah Walker <sarah.walker@imgtec.com>
Fixes:
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||
|---|---|---|
| .. | ||
| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| drm | ||
| dt-bindings | ||
| keys | ||
| kunit | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rv | ||
| scsi | ||
| soc | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| ufs | ||
| vdso | ||
| video | ||
| xen | ||