tree: git://git.linux-mips.org/pub/scm/sjhill/linux-sjhill.git mips-for-linux-next
head: 152e63e374cdc0dc7a321d523dd2930de0acdabf
commit: 0b17c9670590148656645be57f62f279f0d3ad52 [46/72] MIPS: Use queued spinlocks (qspinlock)
config: mips-bigsur_defconfig (attached as .config)
compiler: mips64-linux-gnuabi64-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
wget https://raw.githubusercontent.com/01org/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
git checkout 0b17c9670590148656645be57f62f279f0d3ad52
# save the attached .config to linux build tree
make.cross ARCH=mips
All errors (new ones prefixed by >>):
kernel/locking/qspinlock.c: In function 'queued_spin_lock_slowpath':
>> kernel/locking/qspinlock.c:549:4: error: implicit declaration of function 'prefetchw' [-Werror=implicit-function-declaration]
prefetchw(next);
^~~~~~~~~
cc1: some warnings being treated as errors
vim +/prefetchw +549 kernel/locking/qspinlock.c
8d53fa190 Peter Zijlstra 2016-06-08 533 */
8d53fa190 Peter Zijlstra 2016-06-08 534 smp_read_barrier_depends();
8d53fa190 Peter Zijlstra 2016-06-08 535
a33fda35e Waiman Long 2015-04-24 536 WRITE_ONCE(prev->next, node);
a33fda35e Waiman Long 2015-04-24 537
cd0272fab Waiman Long 2015-11-09 538 pv_wait_node(node, prev);
a33fda35e Waiman Long 2015-04-24 539 arch_mcs_spin_lock_contended(&node->locked);
81b559866 Waiman Long 2015-11-09 540
81b559866 Waiman Long 2015-11-09 541 /*
81b559866 Waiman Long 2015-11-09 542 * While waiting for the MCS lock, the next pointer may have
81b559866 Waiman Long 2015-11-09 543 * been set by another lock waiter. We optimistically load
81b559866 Waiman Long 2015-11-09 544 * the next pointer & prefetch the cacheline for writing
81b559866 Waiman Long 2015-11-09 545 * to reduce latency in the upcoming MCS unlock operation.
81b559866 Waiman Long 2015-11-09 546 */
81b559866 Waiman Long 2015-11-09 547 next = READ_ONCE(node->next);
81b559866 Waiman Long 2015-11-09 548 if (next)
81b559866 Waiman Long 2015-11-09 @549 prefetchw(next);
a33fda35e Waiman Long 2015-04-24 550 }
a33fda35e Waiman Long 2015-04-24 551
a33fda35e Waiman Long 2015-04-24 552 /*
c1fb159db Peter Zijlstra (Intel 2015-04-24 553) * we're at the head of the waitqueue, wait for the owner & pending to
c1fb159db Peter Zijlstra (Intel 2015-04-24 554) * go away.
a33fda35e Waiman Long 2015-04-24 555 *
c1fb159db Peter Zijlstra (Intel 2015-04-24 556) * *,x,y -> *,0,0
2c83e8e94 Waiman Long 2015-04-24 557 *
:::::: The code at line 549 was first introduced by commit
:::::: 81b5598665a24083dd889fbd8cb08b0d8de4b8ad locking/qspinlock: Prefetch the next node cacheline
:::::: TO: Waiman Long <Waiman.Long@xxxxxxx>
:::::: CC: Ingo Molnar <mingo@xxxxxxxxxx>
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