On 15-Mar-2016 7:19 pm, "Cihangir Akturk" <[email protected]> wrote: > > On Thu, Mar 10, 2016 at 02:59:31PM +0530, Chetan Nanda wrote: > > Hi, > > > > As per book (Linux kernel development) > > > > "Whoever locked a mutex must unlock it.That is, you cannot lock a mutex in one > > context and then unlock it in another > > " > > but 'mutex_unlock' code is not checking the owner field at all. > > If you look at the definition of mutex structure in mutex.h:50, > you'll see that the owner field will be compiled in if one of > CONFIG_DEBUG_MUTEXES or CONFIG_MUTEX_SPIN_ON_OWNER is defined. > > And debug_mutex_unlock function in mutex-debug.c:72 will check > the owner and emits warning if it finds out that the mutex isn't > unlocked by its owner. > > http://lxr.free-electrons.com/source/include/linux/mutex.h#L50 > http://lxr.free-electrons.com/source/kernel/locking/mutex-debug.c#L72 > Thanks for your mail, in my kernel CONFIG_MUTEX_SPIN_ON_OWNER is enabled but CONFIG_DEBUG_MUTEX is not enabled. So there are no warning messages in logs.
Also, it don't seems to be a real performance hit by adding a single check of owner with current in unlock code. > > > > Also, I tried with locking the mutex from normal process context and > > unlocking from separate context (work context) and it is allowed > > without any error from kernel. > > > > Is it the mutex user responsibility to keep track of it? Ideally > > mutex_unlock should check if owner is same as current?
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