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Tue, 8 Sep 2026 11:26:20 +0000 (GMT) From: Jan Polensky To: hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com Cc: borntraeger@linux.ibm.com, svens@linux.ibm.com, ciunas@linux.ibm.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] s390/rwlock: Add contention tracepoints to rwlock slowpath Date: Tue, 8 Sep 2026 13:26:07 +0200 Message-ID: <20260908112607.828469-1-japo@linux.ibm.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTA4MDExNyBTYWx0ZWRfXxmZexCEm8m0/ 5VZ6Oj/yn8PDpCREQl8VtFXlQdVEi6/418mAVIsi8eSG2/Xi8tAU+qM12Y2GsBIdkL6TCXR3fbl bwHrI+SGndqk9I8J9snE5UXl0XEkEl4= X-Proofpoint-ORIG-GUID: H5-Rwavw12wlNa_84TNdvAWUZHQDmjVy X-Authority-Analysis: v=2.4 cv=NMDlPU6g c=1 sm=1 tr=0 ts=6a9ff0e2 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=YYcdB7fvNfgyQl8EhqgA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTA4MDExNyBTYWx0ZWRfX3x4rAEtrjcWg H5zGqUtB/fydgh5T8y2rxtSzWtrPbY1ZL3c9zk4Un5JMf75FZuI61ZtIkpsYbcfDXgVcew0JCGp PFzs5rYoAn+V+TwYg7nCpZC+dw8Z8YcvyG14/wkBLttgV8lT6ssf/vQ45L8SwFgxaQeh6B94d4o LAyOctM4q3TF+vI2qxyMNgakXf0868uEtWtIef5swq2LrJ88EEZyDdXwR0UbR1EYQfr2zZLJv0w 1uJeSM2WOlNtzUlsOmVsu/Tv+FXFk6PtRc7a47n9QOliVdtelwIAyDKAbPAAonjmyj8CACZrjvf a2RaV6VfE/C768uVMYAexWVEbD29n29kWr/tFxyOxat5ifmZKm1NqoqXahG2rZ6Y3BpOiV/i0xr wSJvvG72ZBpQRJL0AiZf34wVm49Hxku3ZCityh3DEH3+dcENCFKde2/A7Ay3zu8V9Gxe+rsmGr6 +8DBZcp0sBu9R3vO0MQ== X-Proofpoint-GUID: H5-Rwavw12wlNa_84TNdvAWUZHQDmjVy X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-08_02,2026-09-07_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 spamscore=0 lowpriorityscore=0 clxscore=1015 adultscore=0 impostorscore=0 bulkscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609080117 Instrument arch_read_lock_wait() and arch_write_lock_wait() with trace_contention_begin() and trace_contention_end(). These tracepoints are used by lock contention analysis tools such as perf lock contention to identify contended rwlocks and measure wait times. The generic implementation in kernel/locking/qrwlock.c already emits the same events from its read and write slowpaths. For arch_read_lock_wait(), the in_interrupt() fast-path is intentionally left outside the tracepoint scope. That path spins without entering the wait queue, so it does not represent queue-based contention and its duration is not comparable to the normal slowpath. This matches the behaviour of queued_read_lock_slowpath() in qrwlock.c. The include for is already present from commit ffa796cc1f45 ("s390/spinlock: Add contention tracepoints to lock slowpath"). Signed-off-by: Jan Polensky --- arch/s390/lib/spinlock.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c index dbabca35c008..9094617a5e00 100644 --- a/arch/s390/lib/spinlock.c +++ b/arch/s390/lib/spinlock.c @@ -316,6 +316,7 @@ void arch_read_lock_wait(arch_rwlock_t *rw) return; } + trace_contention_begin(rw, LCB_F_SPIN | LCB_F_READ); /* Remove this reader again to allow recursive read locking */ __atomic_add_const(-1, &rw->cnts); /* Put the reader into the wait queue */ @@ -326,6 +327,7 @@ void arch_read_lock_wait(arch_rwlock_t *rw) while (READ_ONCE(rw->cnts) & 0x10000) barrier(); arch_spin_unlock(&rw->wait); + trace_contention_end(rw, 0); } EXPORT_SYMBOL(arch_read_lock_wait); @@ -333,6 +335,7 @@ void arch_write_lock_wait(arch_rwlock_t *rw) { int old; + trace_contention_begin(rw, LCB_F_SPIN | LCB_F_WRITE); /* Add this CPU to the write waiters */ __atomic_add(0x20000, &rw->cnts); @@ -349,6 +352,7 @@ void arch_write_lock_wait(arch_rwlock_t *rw) } arch_spin_unlock(&rw->wait); + trace_contention_end(rw, 0); } EXPORT_SYMBOL(arch_write_lock_wait); -- 2.53.0