From: paulmck@kernel.org
To: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
kernel-team@fb.com, mingo@kernel.org
Cc: elver@google.com, andreyknvl@google.com, glider@google.com,
dvyukov@google.com, cai@lca.pw, boqun.feng@gmail.com,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH kcsan 17/32] kcsan: Introduce ASSERT_EXCLUSIVE_* macros
Date: Mon, 9 Mar 2020 12:04:05 -0700 [thread overview]
Message-ID: <20200309190420.6100-17-paulmck@kernel.org> (raw)
In-Reply-To: <20200309190359.GA5822@paulmck-ThinkPad-P72>
From: Marco Elver <elver@google.com>
Introduces ASSERT_EXCLUSIVE_WRITER and ASSERT_EXCLUSIVE_ACCESS, which
may be used to assert properties of synchronization logic, where
violation cannot be detected as a normal data race.
Examples of the reports that may be generated:
==================================================================
BUG: KCSAN: assert: race in test_thread / test_thread
write to 0xffffffffab3d1540 of 8 bytes by task 466 on cpu 2:
test_thread+0x8d/0x111
debugfs_write.cold+0x32/0x44
...
assert no writes to 0xffffffffab3d1540 of 8 bytes by task 464 on cpu 0:
test_thread+0xa3/0x111
debugfs_write.cold+0x32/0x44
...
==================================================================
==================================================================
BUG: KCSAN: assert: race in test_thread / test_thread
assert no accesses to 0xffffffffab3d1540 of 8 bytes by task 465 on cpu 1:
test_thread+0xb9/0x111
debugfs_write.cold+0x32/0x44
...
read to 0xffffffffab3d1540 of 8 bytes by task 464 on cpu 0:
test_thread+0x77/0x111
debugfs_write.cold+0x32/0x44
...
==================================================================
Signed-off-by: Marco Elver <elver@google.com>
Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
include/linux/kcsan-checks.h | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/include/linux/kcsan-checks.h b/include/linux/kcsan-checks.h
index 5dcadc2..cf69617 100644
--- a/include/linux/kcsan-checks.h
+++ b/include/linux/kcsan-checks.h
@@ -96,4 +96,44 @@ static inline void kcsan_check_access(const volatile void *ptr, size_t size,
kcsan_check_access(ptr, size, KCSAN_ACCESS_ATOMIC | KCSAN_ACCESS_WRITE)
#endif
+/**
+ * ASSERT_EXCLUSIVE_WRITER - assert no other threads are writing @var
+ *
+ * Assert that there are no other threads writing @var; other readers are
+ * allowed. This assertion can be used to specify properties of concurrent code,
+ * where violation cannot be detected as a normal data race.
+ *
+ * For example, if a per-CPU variable is only meant to be written by a single
+ * CPU, but may be read from other CPUs; in this case, reads and writes must be
+ * marked properly, however, if an off-CPU WRITE_ONCE() races with the owning
+ * CPU's WRITE_ONCE(), would not constitute a data race but could be a harmful
+ * race condition. Using this macro allows specifying this property in the code
+ * and catch such bugs.
+ *
+ * @var variable to assert on
+ */
+#define ASSERT_EXCLUSIVE_WRITER(var) \
+ __kcsan_check_access(&(var), sizeof(var), KCSAN_ACCESS_ASSERT)
+
+/**
+ * ASSERT_EXCLUSIVE_ACCESS - assert no other threads are accessing @var
+ *
+ * Assert that no other thread is accessing @var (no readers nor writers). This
+ * assertion can be used to specify properties of concurrent code, where
+ * violation cannot be detected as a normal data race.
+ *
+ * For example, in a reference-counting algorithm where exclusive access is
+ * expected after the refcount reaches 0. We can check that this property
+ * actually holds as follows:
+ *
+ * if (refcount_dec_and_test(&obj->refcnt)) {
+ * ASSERT_EXCLUSIVE_ACCESS(*obj);
+ * safely_dispose_of(obj);
+ * }
+ *
+ * @var variable to assert on
+ */
+#define ASSERT_EXCLUSIVE_ACCESS(var) \
+ __kcsan_check_access(&(var), sizeof(var), KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT)
+
#endif /* _LINUX_KCSAN_CHECKS_H */
--
2.9.5
next prev parent reply other threads:[~2020-03-09 19:05 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-09 19:03 [PATCH kcsan 0/32] KCSAN commits for v5.7 Paul E. McKenney
2020-03-09 19:03 ` [PATCH kcsan 01/32] kcsan: Prefer __always_inline for fast-path paulmck
2020-03-09 19:03 ` [PATCH kcsan 02/32] kcsan: Show full access type in report paulmck
2020-03-09 19:03 ` [PATCH kcsan 03/32] kcsan: Rate-limit reporting per data races paulmck
2020-03-09 19:03 ` [PATCH kcsan 04/32] kcsan: Make KCSAN compatible with lockdep paulmck
2020-03-09 19:03 ` [PATCH kcsan 05/32] kcsan: Address missing case with KCSAN_REPORT_VALUE_CHANGE_ONLY paulmck
2020-03-09 19:03 ` [PATCH kcsan 06/32] include/linux: Add instrumented.h infrastructure paulmck
2020-03-09 19:03 ` [PATCH kcsan 07/32] asm-generic, atomic-instrumented: Use generic instrumented.h paulmck
2020-03-09 19:03 ` [PATCH kcsan 08/32] asm-generic, kcsan: Add KCSAN instrumentation for bitops paulmck
2020-03-09 19:03 ` [PATCH kcsan 09/32] iov_iter: Use generic instrumented.h paulmck
2020-03-09 19:03 ` [PATCH kcsan 10/32] copy_to_user, copy_from_user: " paulmck
2020-03-09 19:03 ` [PATCH kcsan 11/32] kcsan: Add docbook header for data_race() paulmck
2020-03-09 19:04 ` [PATCH kcsan 12/32] kcsan: Add option to assume plain aligned writes up to word size are atomic paulmck
2020-03-09 19:04 ` [PATCH kcsan 13/32] kcsan: Clarify Kconfig option KCSAN_IGNORE_ATOMICS paulmck
2020-03-09 19:04 ` [PATCH kcsan 14/32] kcsan: Cleanup of main KCSAN Kconfig option paulmck
2020-03-09 19:04 ` [PATCH kcsan 15/32] kcsan: Fix 0-sized checks paulmck
2020-03-09 19:04 ` [PATCH kcsan 16/32] kcsan: Introduce KCSAN_ACCESS_ASSERT access type paulmck
2020-03-09 19:04 ` paulmck [this message]
2020-03-13 8:52 ` [PATCH kcsan 17/32] kcsan: Introduce ASSERT_EXCLUSIVE_* macros Boqun Feng
2020-03-13 16:15 ` Marco Elver
2020-03-14 2:22 ` Boqun Feng
2020-03-17 11:12 ` Marco Elver
2020-03-19 3:23 ` Boqun Feng
2020-03-20 14:49 ` Marco Elver
2020-03-09 19:04 ` [PATCH kcsan 18/32] kcsan: Add test to generate conflicts via debugfs paulmck
2020-03-09 19:04 ` [PATCH kcsan 19/32] kcsan: Expose core configuration parameters as module params paulmck
2020-03-09 19:04 ` [PATCH kcsan 20/32] kcsan: Fix misreporting if concurrent races on same address paulmck
2020-03-09 19:04 ` [PATCH kcsan 21/32] kcsan: Move interfaces that affects checks to kcsan-checks.h paulmck
2020-03-09 19:04 ` [PATCH kcsan 22/32] compiler.h, seqlock.h: Remove unnecessary kcsan.h includes paulmck
2020-03-09 19:04 ` [PATCH kcsan 23/32] kcsan: Introduce kcsan_value_change type paulmck
2020-03-09 19:04 ` [PATCH kcsan 24/32] kcsan: Add kcsan_set_access_mask() support paulmck
2020-03-09 19:04 ` [PATCH kcsan 25/32] kcsan: Introduce ASSERT_EXCLUSIVE_BITS(var, mask) paulmck
2020-03-09 19:04 ` [PATCH kcsan 26/32] kcsan, trace: Make KCSAN compatible with tracing paulmck
2020-03-09 19:57 ` Steven Rostedt
2020-03-09 20:27 ` Paul E. McKenney
2020-03-09 19:04 ` [PATCH kcsan 27/32] kcsan: Add option to allow watcher interruptions paulmck
2020-03-12 18:03 ` Paul E. McKenney
2020-03-12 18:04 ` Paul E. McKenney
2020-03-13 15:28 ` Marco Elver
2020-03-16 13:56 ` Marco Elver
2020-03-16 15:45 ` Paul E. McKenney
2020-03-16 16:22 ` Marco Elver
2020-03-17 17:13 ` Paul E. McKenney
2020-03-17 17:44 ` Marco Elver
2020-03-18 17:42 ` Marco Elver
2020-03-09 19:04 ` [PATCH kcsan 28/32] kcsan: Add option for verbose reporting paulmck
2020-03-09 19:04 ` [PATCH kcsan 29/32] kcsan: Add current->state to implicitly atomic accesses paulmck
2020-03-09 19:04 ` [PATCH kcsan 30/32] kcsan: Fix a typo in a comment paulmck
2020-03-09 19:04 ` [PATCH kcsan 31/32] kcsan: Update Documentation/dev-tools/kcsan.rst paulmck
2020-03-09 19:04 ` [PATCH kcsan 32/32] kcsan: Update API documentation in kcsan-checks.h paulmck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200309190420.6100-17-paulmck@kernel.org \
--to=paulmck@kernel.org \
--cc=andreyknvl@google.com \
--cc=boqun.feng@gmail.com \
--cc=cai@lca.pw \
--cc=dvyukov@google.com \
--cc=elver@google.com \
--cc=glider@google.com \
--cc=kasan-dev@googlegroups.com \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).