linux-kernel - Re: [PATCH 2/2] rtmutex: Reduce top-waiter blocking on a lock

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Date:   Wed, 11 Apr 2018 20:51:29 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     kbuild-all@...org, peterz@...radead.org, tglx@...utronix.de,
        mingo@...nel.org, longman@...hat.com, dave@...olabs.net,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbues@...e.de>
Subject: Re: [PATCH 2/2] rtmutex: Reduce top-waiter blocking on a lock

Hi Davidlohr,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.16 next-20180411]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Davidlohr-Bueso/locking-rtmutex-Delete-save_state-member-of-struct-rt_mutex/20180411-155733
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

>> kernel/locking/rtmutex_common.h:62:9: sparse: context imbalance in '__rt_mutex_slowlock' - unexpected unlock

vim +/__rt_mutex_slowlock +62 kernel/locking/rtmutex_common.h

23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27  51  
23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27  52  static inline struct rt_mutex_waiter *
23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27  53  rt_mutex_top_waiter(struct rt_mutex *lock)
23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27  54  {
c28d62cf5 kernel/locking/rtmutex_common.h Peter Zijlstra 2018-03-27  55  	struct rb_node *leftmost = rb_first_cached(&lock->waiters);
c28d62cf5 kernel/locking/rtmutex_common.h Peter Zijlstra 2018-03-27  56  	struct rt_mutex_waiter *w = NULL;
23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27  57  
c28d62cf5 kernel/locking/rtmutex_common.h Peter Zijlstra 2018-03-27  58  	if (leftmost) {
c28d62cf5 kernel/locking/rtmutex_common.h Peter Zijlstra 2018-03-27  59  		w = rb_entry(leftmost, struct rt_mutex_waiter, tree_entry);
23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27  60  		BUG_ON(w->lock != lock);
c28d62cf5 kernel/locking/rtmutex_common.h Peter Zijlstra 2018-03-27  61  	}
23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27 @62  	return w;
23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27  63  }
23f78d4a0 kernel/rtmutex_common.h         Ingo Molnar    2006-06-27  64  

:::::: The code at line 62 was first introduced by commit
:::::: 23f78d4a03c53cbd75d87a795378ea540aa08c86 [PATCH] pi-futex: rt mutex core

:::::: TO: Ingo Molnar <mingo@...e.hu>
:::::: CC: Linus Torvalds <torvalds@...osdl.org>

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