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Thu, 03 Jul 2025 13:48:34 -0700 (PDT) Received: from localhost ([2a03:2880:30ff:71::]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae3f6b02788sm37612366b.113.2025.07.03.13.48.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Jul 2025 13:48:34 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Emil Tsalapatis , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Eduard Zingerman , Barret Rhoden , Matt Bobrowski , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v5 08/12] bpf: Report rqspinlock deadlocks/timeout to BPF stderr Date: Thu, 3 Jul 2025 13:48:14 -0700 Message-ID: <20250703204818.925464-9-memxor@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250703204818.925464-1-memxor@gmail.com> References: <20250703204818.925464-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2144; h=from:subject; bh=luDkJ5JCm77sLDhMzbddK7T3ks3tztn4nYuDbC9CsGs=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBoZudMvqxNY2SWaTG61qnufPwtwflTNgAv52Mb+mPP 6qHv2FmJAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCaGbnTAAKCRBM4MiGSL8Rygd9D/ 9JLpvLGtt1wAkUzj6LSYNblrXsj0XV9c0wHnFs4ZJv6Ge2hO9TUG+zacE2hiKzlZqrLv/8RoEWuY7J oe68Ctdo7aPxwlDriIXCBs64JONcvv0wICetBcMHtFI94M89jdvXRY6axT1T6cw5IHos+pFooUBsof ctNW9yYdWFTTGH3M5DcAoLykbFqAFDqX4vG8Vy4VnHXwU0xf/MEEUnWIC4YD1B/z8eDrU7fJsTZj9m AS3V7UI3w1XEbctBJRsqNLsRSktuLC75NEjlwy9iqr88sE302BmX/Fk5UWyh608TLaTkZjXH73hwdc yxPwyDYv9HFcUA+gkjfX5xKjCrwKEtAh1q3BB7b2A1LEzqgluYwW2iHvn+7o34i5Vf/nrl+fRCAGhJ 7DnFzy/P/qmKpJHPl8JgJu5I/L87chMCNdDrvTbIprleO8a399D0qPdm4ecI+2R2as+SeGviceCi16 gZP8RRGSdVX9l/2sdJCWfssep/qCjL9Lygjqobv0rc+KdFLmxdKKTi21Unm6X3NAy7efFQQJN9bmT6 /57Y0SgO+twZFlPuqAnfSVOBMUKMu22zdLVSa6ZQ/gKD3Zij0AXbjvtyBfOw7vNSCpQqMcoXnFH272 cX1/MeWPRHPSmcd6BuHSjNMKmwgeuokg2OZCHZQj275g425aNf8lmLbSv1Kg== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Content-Transfer-Encoding: 8bit Begin reporting rqspinlock deadlocks and timeout to BPF program's stderr. Reviewed-by: Emil Tsalapatis Signed-off-by: Kumar Kartikeya Dwivedi --- kernel/bpf/rqspinlock.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/kernel/bpf/rqspinlock.c b/kernel/bpf/rqspinlock.c index 338305c8852c..5ab354d55d82 100644 --- a/kernel/bpf/rqspinlock.c +++ b/kernel/bpf/rqspinlock.c @@ -666,6 +666,27 @@ EXPORT_SYMBOL_GPL(resilient_queued_spin_lock_slowpath); __bpf_kfunc_start_defs(); +static void bpf_prog_report_rqspinlock_violation(const char *str, void *lock, bool irqsave) +{ + struct rqspinlock_held *rqh = this_cpu_ptr(&rqspinlock_held_locks); + struct bpf_stream_stage ss; + struct bpf_prog *prog; + + prog = bpf_prog_find_from_stack(); + if (!prog) + return; + bpf_stream_stage(ss, prog, BPF_STDERR, ({ + bpf_stream_printk(ss, "ERROR: %s for bpf_res_spin_lock%s\n", str, irqsave ? "_irqsave" : ""); + bpf_stream_printk(ss, "Attempted lock = 0x%px\n", lock); + bpf_stream_printk(ss, "Total held locks = %d\n", rqh->cnt); + for (int i = 0; i < min(RES_NR_HELD, rqh->cnt); i++) + bpf_stream_printk(ss, "Held lock[%2d] = 0x%px\n", i, rqh->locks[i]); + bpf_stream_dump_stack(ss); + })); +} + +#define REPORT_STR(ret) ({ (ret) == -ETIMEDOUT ? "Timeout detected" : "AA or ABBA deadlock detected"; }) + __bpf_kfunc int bpf_res_spin_lock(struct bpf_res_spin_lock *lock) { int ret; @@ -676,6 +697,7 @@ __bpf_kfunc int bpf_res_spin_lock(struct bpf_res_spin_lock *lock) preempt_disable(); ret = res_spin_lock((rqspinlock_t *)lock); if (unlikely(ret)) { + bpf_prog_report_rqspinlock_violation(REPORT_STR(ret), lock, false); preempt_enable(); return ret; } @@ -698,6 +720,7 @@ __bpf_kfunc int bpf_res_spin_lock_irqsave(struct bpf_res_spin_lock *lock, unsign local_irq_save(flags); ret = res_spin_lock((rqspinlock_t *)lock); if (unlikely(ret)) { + bpf_prog_report_rqspinlock_violation(REPORT_STR(ret), lock, true); local_irq_restore(flags); preempt_enable(); return ret; -- 2.47.1