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McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, 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 6/9] rcu: Upgrade sync_exp_work_done() to smp_mb() Date: Thu, 30 May 2019 08:00:12 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190530145942.GA30318@linux.ibm.com> References: <20190530145942.GA30318@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19053015-0040-0000-0000-000004F68299 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011185; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01210785; UDB=6.00636158; IPR=6.00991820; MB=3.00027120; MTD=3.00000008; XFM=3.00000015; UTC=2019-05-30 15:00:22 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19053015-0041-0000-0000-000009029CE2 Message-Id: <20190530150015.30995-6-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-05-30_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=15 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-1905300106 Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org The sync_exp_work_done() function uses smp_mb__before_atomic(), but there is no obvious atomic in the ensuing code. The ordering is absolutely required for grace periods to work correctly, so this commit upgrades the smp_mb__before_atomic() to smp_mb(). Reported-by: Andrea Parri Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_exp.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 9c990df880d1..d969650a72c6 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -259,8 +259,7 @@ static bool sync_exp_work_done(unsigned long s) { if (rcu_exp_gp_seq_done(s)) { trace_rcu_exp_grace_period(rcu_state.name, s, TPS("done")); - /* Ensure test happens before caller kfree(). */ - smp_mb__before_atomic(); /* ^^^ */ + smp_mb(); /* Ensure test happens before caller kfree(). */ return true; } return false; -- 2.17.1