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McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E . McKenney" Subject: [PATCH tip/core/rcu 7/8] rcu: Add sparse check to rcu_assign_pointer() Date: Wed, 9 Jan 2019 13:41:41 -0800 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190109214115.GA2835@linux.ibm.com> References: <20190109214115.GA2835@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19010921-0060-0000-0000-000002F64125 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010375; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000274; SDB=6.01144149; UDB=6.00595711; IPR=6.00924411; MB=3.00025056; MTD=3.00000008; XFM=3.00000015; UTC=2019-01-09 21:41:49 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19010921-0061-0000-0000-000047DC77C2 Message-Id: <20190109214142.4428-7-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-09_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901090172 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Joel Fernandes (Google)" The rcu_assign_pointer() function currently doesn't do any sparse checking on the assigned-to pointer. So its possible that a pointer that is not __rcu annotated is assigned with rcu_assign_pointer without sparse complaints. Because rcu_dereference() already does such checking, this commit makes rcu_assign_pointer() to do the same. The extra error could be helpful in cases where an RCU pointer is assigned with rcu_assign_pointer() but not annotated with __rcu. This doesn't generate any code in the normal case because __CHECKER__ is defined only in the context of sparse. This commit also renames rcu_dereference_sparse() to rcu_check_parse() since the checking now happens not only during derereferencing but also during assignment. Test: Introduced an rcu_assign_pointer in code and checked the output of sparse with and without this change. The change correctly causes sparse to throw an error. Signed-off-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index b4e99639d6d4..0bb5d906bff3 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -309,16 +309,16 @@ static inline void rcu_preempt_sleep_check(void) { } */ #ifdef __CHECKER__ -#define rcu_dereference_sparse(p, space) \ +#define rcu_check_sparse(p, space) \ ((void)(((typeof(*p) space *)p) == p)) #else /* #ifdef __CHECKER__ */ -#define rcu_dereference_sparse(p, space) +#define rcu_check_sparse(p, space) #endif /* #else #ifdef __CHECKER__ */ #define __rcu_access_pointer(p, space) \ ({ \ typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \ - rcu_dereference_sparse(p, space); \ + rcu_check_sparse(p, space); \ ((typeof(*p) __force __kernel *)(_________p1)); \ }) #define __rcu_dereference_check(p, c, space) \ @@ -326,13 +326,13 @@ static inline void rcu_preempt_sleep_check(void) { } /* Dependency order vs. p above. */ \ typeof(*p) *________p1 = (typeof(*p) *__force)READ_ONCE(p); \ RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \ - rcu_dereference_sparse(p, space); \ + rcu_check_sparse(p, space); \ ((typeof(*p) __force __kernel *)(________p1)); \ }) #define __rcu_dereference_protected(p, c, space) \ ({ \ RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \ - rcu_dereference_sparse(p, space); \ + rcu_check_sparse(p, space); \ ((typeof(*p) __force __kernel *)(p)); \ }) #define rcu_dereference_raw(p) \ @@ -382,6 +382,7 @@ static inline void rcu_preempt_sleep_check(void) { } #define rcu_assign_pointer(p, v) \ ({ \ uintptr_t _r_a_p__v = (uintptr_t)(v); \ + rcu_check_sparse(p, __rcu); \ \ if (__builtin_constant_p(v) && (_r_a_p__v) == (uintptr_t)NULL) \ WRITE_ONCE((p), (typeof(p))(_r_a_p__v)); \ @@ -785,7 +786,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) */ #define RCU_INIT_POINTER(p, v) \ do { \ - rcu_dereference_sparse(p, __rcu); \ + rcu_check_sparse(p, __rcu); \ WRITE_ONCE(p, RCU_INITIALIZER(v)); \ } while (0) -- 2.17.1