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[210.128.90.14]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-7fc9c305637sm6632872a12.32.2024.12.01.17.21.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 Dec 2024 17:21:11 -0800 (PST) From: Ryo Takakura To: peterz@infradead.org, mingo@redhat.com, will@kernel.org, longman@redhat.com, boqun.feng@gmail.com, bigeasy@linutronix.de, clrkwllms@kernel.org, rostedt@goodmis.org, tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Ryo Takakura Subject: [PATCH] lockdep: Fix wait context check on softirq for PREEMPT_RT Date: Mon, 2 Dec 2024 10:20:17 +0900 Message-Id: <20241202012017.14910-1-ryotkkr98@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Commit 0c1d7a2c2d32 ("lockdep: Remove softirq accounting on PREEMPT_RT.") stopped updating @softirq_context on PREEMPT_RT to ignore "inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage" as the report accounts softirq context which PREEMPT_RT doesn't have to. However, wait context check still needs to report mutex usage within softirq, even when its threaded on PREEMPT_RT. The check is failing to report the usage as task_wait_context() checks if its in softirq by referencing @softirq_context, ending up not assigning the correct wait type of LD_WAIT_CONFIG for PREEMPT_RT's softirq. [ 0.184549] | wait context tests | [ 0.184549] -------------------------------------------------------------------------- [ 0.184549] | rcu | raw | spin |mutex | [ 0.184549] -------------------------------------------------------------------------- [ 0.184550] in hardirq context: ok | ok | ok | ok | [ 0.185083] in hardirq context (not threaded): ok | ok | ok | ok | [ 0.185606] in softirq context: ok | ok | ok |FAILED| Account softirq context but only when !PREEMPT_RT so that task_wait_context() returns LD_WAIT_CONFIG as intended. Signed-off-by: Ryo Takakura --- Hi! I wasn't able come up with a way to fix the wait context test while keeping the commit 0c1d7a2c2d32 ("lockdep: Remove softirq accounting on PREEMPT_RT.") without referencing @softirq_context... Hoping to get a feedback on it! Also I wonder if the test can be skipped as I believe its taken care by spinlock wait context test since the PREEMPT_RT's softirq context is protected by local_lock which is mapped to rt_spinlock. Thanks! Ryo Takakura --- include/linux/irqflags.h | 2 +- kernel/locking/lockdep.c | 11 +++++++---- 2 files changed, 8 insertions(+), 5 deletions(-) diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h index 3f003d5fd..c33c3bbd8 100644 --- a/include/linux/irqflags.h +++ b/include/linux/irqflags.h @@ -121,7 +121,7 @@ do { \ # define lockdep_irq_work_exit(__work) do { } while (0) #endif -#if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PREEMPT_RT) +#if defined(CONFIG_TRACE_IRQFLAGS) # define lockdep_softirq_enter() \ do { \ current->softirq_context++; \ diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 536bd4715..2a508d6a6 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -4602,7 +4602,7 @@ mark_usage(struct task_struct *curr, struct held_lock *hlock, int check) if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ_READ)) return 0; - if (curr->softirq_context) + if (!IS_ENABLED(CONFIG_PREEMPT_RT) && curr->softirq_context) if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ_READ)) return 0; @@ -4610,7 +4610,7 @@ mark_usage(struct task_struct *curr, struct held_lock *hlock, int check) if (lockdep_hardirq_context()) if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ)) return 0; - if (curr->softirq_context) + if (!IS_ENABLED(CONFIG_PREEMPT_RT) && curr->softirq_context) if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ)) return 0; } @@ -4651,8 +4651,11 @@ mark_usage(struct task_struct *curr, struct held_lock *hlock, int check) static inline unsigned int task_irq_context(struct task_struct *task) { - return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() + - LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context; + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context(); + else + return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() + + LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context; } static int separate_irq_context(struct task_struct *curr, -- 2.34.1