From: kbuild test robot <lkp@intel.com>
To: Marco Elver <elver@google.com>
Cc: kbuild-all@lists.01.org, elver@google.com, akiyks@gmail.com,
stern@rowland.harvard.edu, glider@google.com,
parri.andrea@gmail.com, andreyknvl@google.com, luto@kernel.org,
ard.biesheuvel@linaro.org, arnd@arndb.de, boqun.feng@gmail.com,
bp@alien8.de, dja@axtens.net, dlustig@nvidia.com,
dave.hansen@linux.intel.com, dhowells@redhat.com,
dvyukov@google.com, hpa@zytor.com, mingo@redhat.com,
j.alglave@ucl.ac.uk, joel@joelfernandes.org, corbet@lwn.net,
jpoimboe@redhat.com, luc.maranget@inria.fr, mark.rutland@arm.com,
npiggin@gmail.com, paulmck@kernel.org, peterz@infradead.org,
tglx@linutronix.de, will@kernel.org, kasan-dev@googlegroups.com,
linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
linux-efi@vger.kernel.org, linux-kbuild@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org
Subject: Re: [PATCH v3 5/9] seqlock, kcsan: Add annotations for KCSAN
Date: Tue, 5 Nov 2019 19:35:15 +0800 [thread overview]
Message-ID: <201911051950.7sv6Mqoe%lkp@intel.com> (raw)
In-Reply-To: <20191104142745.14722-6-elver@google.com>
Hi Marco,
I love your patch! Perhaps something to improve:
[auto build test WARNING on linus/master]
[also build test WARNING on v5.4-rc6]
[cannot apply to next-20191031]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
url: https://github.com/0day-ci/linux/commits/Marco-Elver/Add-Kernel-Concurrency-Sanitizer-KCSAN/20191105-002542
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git a99d8080aaf358d5d23581244e5da23b35e340b9
reproduce:
# apt-get install sparse
# sparse version: v0.6.1-6-g57f8611-dirty
make ARCH=x86_64 allmodconfig
make C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>
sparse warnings: (new ones prefixed by >>)
>> include/linux/rcupdate.h:651:9: sparse: sparse: context imbalance in 'thread_group_cputime' - different lock contexts for basic block
vim +/thread_group_cputime +651 include/linux/rcupdate.h
^1da177e4c3f41 Linus Torvalds 2005-04-16 603
^1da177e4c3f41 Linus Torvalds 2005-04-16 604 /*
^1da177e4c3f41 Linus Torvalds 2005-04-16 605 * So where is rcu_write_lock()? It does not exist, as there is no
^1da177e4c3f41 Linus Torvalds 2005-04-16 606 * way for writers to lock out RCU readers. This is a feature, not
^1da177e4c3f41 Linus Torvalds 2005-04-16 607 * a bug -- this property is what provides RCU's performance benefits.
^1da177e4c3f41 Linus Torvalds 2005-04-16 608 * Of course, writers must coordinate with each other. The normal
^1da177e4c3f41 Linus Torvalds 2005-04-16 609 * spinlock primitives work well for this, but any other technique may be
^1da177e4c3f41 Linus Torvalds 2005-04-16 610 * used as well. RCU does not care how the writers keep out of each
^1da177e4c3f41 Linus Torvalds 2005-04-16 611 * others' way, as long as they do so.
^1da177e4c3f41 Linus Torvalds 2005-04-16 612 */
3d76c082907e8f Paul E. McKenney 2009-09-28 613
3d76c082907e8f Paul E. McKenney 2009-09-28 614 /**
ca5ecddfa8fcbd Paul E. McKenney 2010-04-28 615 * rcu_read_unlock() - marks the end of an RCU read-side critical section.
3d76c082907e8f Paul E. McKenney 2009-09-28 616 *
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 617 * In most situations, rcu_read_unlock() is immune from deadlock.
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 618 * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock()
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 619 * is responsible for deboosting, which it does via rt_mutex_unlock().
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 620 * Unfortunately, this function acquires the scheduler's runqueue and
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 621 * priority-inheritance spinlocks. This means that deadlock could result
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 622 * if the caller of rcu_read_unlock() already holds one of these locks or
ec84b27f9b3b56 Anna-Maria Gleixner 2018-05-25 623 * any lock that is ever acquired while holding them.
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 624 *
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 625 * That said, RCU readers are never priority boosted unless they were
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 626 * preempted. Therefore, one way to avoid deadlock is to make sure
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 627 * that preemption never happens within any RCU read-side critical
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 628 * section whose outermost rcu_read_unlock() is called with one of
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 629 * rt_mutex_unlock()'s locks held. Such preemption can be avoided in
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 630 * a number of ways, for example, by invoking preempt_disable() before
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 631 * critical section's outermost rcu_read_lock().
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 632 *
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 633 * Given that the set of locks acquired by rt_mutex_unlock() might change
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 634 * at any time, a somewhat more future-proofed approach is to make sure
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 635 * that that preemption never happens within any RCU read-side critical
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 636 * section whose outermost rcu_read_unlock() is called with irqs disabled.
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 637 * This approach relies on the fact that rt_mutex_unlock() currently only
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 638 * acquires irq-disabled locks.
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 639 *
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 640 * The second of these two approaches is best in most situations,
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 641 * however, the first approach can also be useful, at least to those
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 642 * developers willing to keep abreast of the set of locks acquired by
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 643 * rt_mutex_unlock().
f27bc4873fa8b7 Paul E. McKenney 2014-05-04 644 *
3d76c082907e8f Paul E. McKenney 2009-09-28 645 * See rcu_read_lock() for more information.
3d76c082907e8f Paul E. McKenney 2009-09-28 646 */
bc33f24bdca8b6 Paul E. McKenney 2009-08-22 647 static inline void rcu_read_unlock(void)
bc33f24bdca8b6 Paul E. McKenney 2009-08-22 648 {
f78f5b90c4ffa5 Paul E. McKenney 2015-06-18 649 RCU_LOCKDEP_WARN(!rcu_is_watching(),
bde23c6892878e Heiko Carstens 2012-02-01 650 "rcu_read_unlock() used illegally while idle");
bc33f24bdca8b6 Paul E. McKenney 2009-08-22 @651 __release(RCU);
bc33f24bdca8b6 Paul E. McKenney 2009-08-22 652 __rcu_read_unlock();
d24209bb689e2c Paul E. McKenney 2015-01-21 653 rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */
bc33f24bdca8b6 Paul E. McKenney 2009-08-22 654 }
^1da177e4c3f41 Linus Torvalds 2005-04-16 655
:::::: The code at line 651 was first introduced by commit
:::::: bc33f24bdca8b6e97376e3a182ab69e6cdefa989 rcu: Consolidate sparse and lockdep declarations in include/linux/rcupdate.h
:::::: TO: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
:::::: CC: Ingo Molnar <mingo@elte.hu>
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
next prev parent reply other threads:[~2019-11-05 11:35 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-04 14:27 [PATCH v3 0/9] Add Kernel Concurrency Sanitizer (KCSAN) Marco Elver
2019-11-04 14:27 ` [PATCH v3 1/9] kcsan: Add Kernel Concurrency Sanitizer infrastructure Marco Elver
2019-11-06 9:38 ` Dmitry Vyukov
2019-11-06 10:03 ` Marco Elver
2019-11-06 19:11 ` Marco Elver
2019-11-06 19:59 ` kbuild test robot
2019-11-06 20:34 ` kbuild test robot
2019-11-07 18:43 ` Marco Elver
2019-11-07 21:08 ` Bhupesh Sharma
2019-11-08 14:23 ` Marco Elver
2019-11-04 14:27 ` [PATCH v3 2/9] kcsan: Add Documentation entry in dev-tools Marco Elver
2019-11-04 14:27 ` [PATCH v3 3/9] objtool, kcsan: Add KCSAN runtime functions to whitelist Marco Elver
2019-11-04 14:27 ` [PATCH v3 4/9] build, kcsan: Add KCSAN build exceptions Marco Elver
2019-11-04 14:27 ` [PATCH v3 5/9] seqlock, kcsan: Add annotations for KCSAN Marco Elver
2019-11-05 11:35 ` kbuild test robot [this message]
2019-11-05 15:22 ` Marco Elver
2019-11-04 14:27 ` [PATCH v3 6/9] seqlock: Require WRITE_ONCE surrounding raw_seqcount_barrier Marco Elver
2019-11-04 14:27 ` [PATCH v3 7/9] asm-generic, kcsan: Add KCSAN instrumentation for bitops Marco Elver
2019-11-04 14:27 ` [PATCH v3 8/9] locking/atomics, kcsan: Add KCSAN instrumentation Marco Elver
2019-11-04 14:27 ` [PATCH v3 9/9] x86, kcsan: Enable KCSAN for x86 Marco Elver
2019-11-04 16:47 ` [PATCH v3 0/9] Add Kernel Concurrency Sanitizer (KCSAN) Paul E. McKenney
2019-11-04 18:41 ` Marco Elver
2019-11-04 19:46 ` Paul E. McKenney
2019-11-05 11:10 ` Marco Elver
2019-11-05 14:20 ` Paul E. McKenney
2019-11-05 15:25 ` Marco Elver
2019-11-14 18:05 ` Marco Elver
2019-11-14 19:48 ` Paul E. McKenney
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