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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 11/20] doc: rcu: Add more rationale for using rcu_read_lock_sched in checklist Date: Sun, 11 Nov 2018 11:56:36 -0800 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181111195619.GA6958@linux.ibm.com> References: <20181111195619.GA6958@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18111119-0072-0000-0000-000003C6F416 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010028; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000270; SDB=6.01116023; UDB=6.00577118; IPR=6.00896124; MB=3.00024114; MTD=3.00000008; XFM=3.00000015; UTC=2018-11-11 19:56:51 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18111119-0073-0000-0000-00004A134C09 Message-Id: <20181111195645.9205-11-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-11_13:,, 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=8.0.1-1807170000 definitions=main-1811110190 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Joel Fernandes (Google)" This commit explains why rcu_read_lock_sched is better than using preempt_disable. Signed-off-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- Documentation/RCU/checklist.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt index 49747717d905..8860ab2a897a 100644 --- a/Documentation/RCU/checklist.txt +++ b/Documentation/RCU/checklist.txt @@ -63,7 +63,7 @@ over a rather long period of time, but improvements are always welcome! pointer must be covered by rcu_read_lock(), rcu_read_lock_bh(), rcu_read_lock_sched(), or by the appropriate update-side lock. Disabling of preemption can serve as rcu_read_lock_sched(), but - is less readable. + is less readable and prevents lockdep from detecting locking issues. Letting RCU-protected pointers "leak" out of an RCU read-side critical section is every bid as bad as letting them leak out -- 2.17.1