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McKenney" To: oleg@redhat.com, peterz@infradead.org Cc: linux-kernel@vger.kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com Subject: [PATCH RFC kenrel/rcu] Eliminate BUG_ON() for sync.c Reply-To: paulmck@linux.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18102214-0072-0000-0000-000003B9D3F0 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009916; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000268; SDB=6.01106373; UDB=6.00572935; IPR=6.00886457; MB=3.00023857; MTD=3.00000008; XFM=3.00000015; UTC=2018-10-22 14:52:45 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18102214-0073-0000-0000-000049D7F1A0 Message-Id: <20181022145241.GA7488@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-10-22_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=772 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1810220127 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The sync.c 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 changes these BUG_ON() calls to WARN_ON_ONCE(), but does so quite naively. Improved changes welcome. ;-) Reported-by: Linus Torvalds Signed-off-by: Paul E. McKenney Cc: Oleg Nesterov Cc: Peter Zijlstra diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c index 3f943efcf61c..28ac78ba0656 100644 --- a/kernel/rcu/sync.c +++ b/kernel/rcu/sync.c @@ -125,12 +125,12 @@ void rcu_sync_enter(struct rcu_sync *rsp) rsp->gp_state = GP_PENDING; spin_unlock_irq(&rsp->rss_lock); - BUG_ON(need_wait && need_sync); - if (need_sync) { gp_ops[rsp->gp_type].sync(); rsp->gp_state = GP_PASSED; wake_up_all(&rsp->gp_wait); + if (WARN_ON_ONCE(need_wait)) + wait_event(rsp->gp_wait, rsp->gp_state == GP_PASSED); } else if (need_wait) { wait_event(rsp->gp_wait, rsp->gp_state == GP_PASSED); } else { @@ -139,7 +139,7 @@ void rcu_sync_enter(struct rcu_sync *rsp) * Nobody has yet been allowed the 'fast' path and thus we can * avoid doing any sync(). The callback will get 'dropped'. */ - BUG_ON(rsp->gp_state != GP_PASSED); + WARN_ON_ONCE(rsp->gp_state != GP_PASSED); } } @@ -166,8 +166,8 @@ static void rcu_sync_func(struct rcu_head *rhp) struct rcu_sync *rsp = container_of(rhp, struct rcu_sync, cb_head); unsigned long flags; - BUG_ON(rsp->gp_state != GP_PASSED); - BUG_ON(rsp->cb_state == CB_IDLE); + WARN_ON_ONCE(rsp->gp_state != GP_PASSED); + WARN_ON_ONCE(rsp->cb_state == CB_IDLE); spin_lock_irqsave(&rsp->rss_lock, flags); if (rsp->gp_count) { @@ -225,7 +225,7 @@ void rcu_sync_dtor(struct rcu_sync *rsp) { int cb_state; - BUG_ON(rsp->gp_count); + WARN_ON_ONCE(rsp->gp_count); spin_lock_irq(&rsp->rss_lock); if (rsp->cb_state == CB_REPLAY) @@ -235,6 +235,6 @@ void rcu_sync_dtor(struct rcu_sync *rsp) if (cb_state != CB_IDLE) { gp_ops[rsp->gp_type].wait(); - BUG_ON(rsp->cb_state != CB_IDLE); + WARN_ON_ONCE(rsp->cb_state != CB_IDLE); } }