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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 3/4] rcu: Eliminate BUG_ON() for kernel/rcu/tree_plugin.h Date: Sun, 11 Nov 2018 11:32:16 -0800 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181111193156.GA3666@linux.ibm.com> References: <20181111193156.GA3666@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18111119-0060-0000-0000-000002D0FBB5 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010028; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000270; SDB=6.01116015; UDB=6.00578730; IPR=6.00896116; MB=3.00024114; MTD=3.00000008; XFM=3.00000015; UTC=2018-11-11 19:32:22 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18111119-0061-0000-0000-0000472A0171 Message-Id: <20181111193217.4010-3-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-1811110185 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The tree_plugin.h file has a number of calls to BUG_ON(), which panics the kernel, which is not a good strategy for devices (like embedded) that don't have a way to capture console output. This commit therefore converts these BUG_ON() calls to WARN_ON_ONCE() and WARN_ONCE(). Reported-by: Linus Torvalds Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 05915e536336..105a19752ac2 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1464,7 +1464,8 @@ static void __init rcu_spawn_boost_kthreads(void) for_each_possible_cpu(cpu) per_cpu(rcu_cpu_has_work, cpu) = 0; - BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); + if (WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec), "%s: Could not start rcuo kthread, OOM is now expected behavior\n", __func__)) + return; rcu_for_each_leaf_node(rnp) (void)rcu_spawn_one_boost_kthread(rnp); } @@ -2322,7 +2323,8 @@ static int rcu_nocb_kthread(void *arg) tail = rdp->nocb_follower_tail; rdp->nocb_follower_tail = &rdp->nocb_follower_head; raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); - BUG_ON(!list); + if (WARN_ON_ONCE(!list)) + continue; trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeNonEmpty")); /* Each pass through the following loop invokes a callback. */ @@ -2495,7 +2497,8 @@ static void rcu_spawn_one_nocb_kthread(int cpu) /* Spawn the kthread for this CPU. */ t = kthread_run(rcu_nocb_kthread, rdp_spawn, "rcuo%c/%d", rcu_state.abbr, cpu); - BUG_ON(IS_ERR(t)); + if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo kthread, OOM is now expected behavior\n", __func__)) + return; WRITE_ONCE(rdp_spawn->nocb_kthread, t); } -- 2.17.1