From nobody Sat Sep 13 20:17:39 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C75BBC636CC for ; Tue, 31 Jan 2023 14:23:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229997AbjAaOXF (ORCPT ); Tue, 31 Jan 2023 09:23:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231872AbjAaOWc (ORCPT ); Tue, 31 Jan 2023 09:22:32 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 06802222D1; Tue, 31 Jan 2023 06:22:31 -0800 (PST) Date: Tue, 31 Jan 2023 14:22:28 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1675174948; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9Um5LKI/9hScNlYvhBVuAMl7qOTHMQENc5JKgiBOlKk=; b=fF/OfaSloyV3VbAU3W/Pcrt1QcvvFFea2BgWT4FK5A+UleMEXNcAkd7BWdU7hBB3IbqqON zMlyi48csIlUJvOzFY6JDap27BrBjee6/CmRw6RvYbM7/l09nNMmwrzXPKeowHsS2e1ENg oyNL/OHq8F9V18/Jx+rVxKmxKcJUBh7vCedqQfkowf8H/EJwPwJvjNUXizPRNit/88kKIM MGyXlL9i8UltdYiQv3vUnTIiT5vNlGrbdW0b/Vaj5QOkiDpEptgP1Xf8ZRg8t5pp21pU/o GHOFoLm2s+8feYzJT9XcI1sUYKhSK56QhhkyFFRuZy+8UoiyMH9E3ovHEF8Eog== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1675174948; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9Um5LKI/9hScNlYvhBVuAMl7qOTHMQENc5JKgiBOlKk=; b=/9nnECGq4EUylg9Z3bJRH4RBnUUJBWnfygUW3LUVonxRr+QZZ4gfGEJKMG8iAd5ErPg9wQ aDInwWqIqsLK+ACQ== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] cpuidle: lib/bug: Disable rcu_is_watching() during WARN/BUG Cc: "Peter Zijlstra (Intel)" , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230126151323.408156109@infradead.org> References: <20230126151323.408156109@infradead.org> MIME-Version: 1.0 Message-ID: <167517494843.4906.16680899245524839121.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 5a5d7e9badd2cb8065db171961bd30bd3595e4b6 Gitweb: https://git.kernel.org/tip/5a5d7e9badd2cb8065db171961bd30bd3= 595e4b6 Author: Peter Zijlstra AuthorDate: Thu, 26 Jan 2023 16:08:31 +01:00 Committer: Ingo Molnar CommitterDate: Tue, 31 Jan 2023 15:01:45 +01:00 cpuidle: lib/bug: Disable rcu_is_watching() during WARN/BUG In order to avoid WARN/BUG from generating nested or even recursive warnings, force rcu_is_watching() true during WARN/lockdep_rcu_suspicious(). Notably things like unwinding the stack can trigger rcu_dereference() warnings, which then triggers more unwinding which then triggers more warnings etc.. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20230126151323.408156109@infradead.org --- include/linux/context_tracking.h | 27 +++++++++++++++++++++++++++ kernel/locking/lockdep.c | 3 +++ kernel/panic.c | 5 +++++ lib/bug.c | 15 ++++++++++++++- 4 files changed, 49 insertions(+), 1 deletion(-) diff --git a/include/linux/context_tracking.h b/include/linux/context_track= ing.h index dcef4a9..d4afa85 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -130,9 +130,36 @@ static __always_inline unsigned long ct_state_inc(int = incby) return arch_atomic_add_return(incby, this_cpu_ptr(&context_tracking.state= )); } =20 +static __always_inline bool warn_rcu_enter(void) +{ + bool ret =3D false; + + /* + * Horrible hack to shut up recursive RCU isn't watching fail since + * lots of the actual reporting also relies on RCU. + */ + preempt_disable_notrace(); + if (rcu_dynticks_curr_cpu_in_eqs()) { + ret =3D true; + ct_state_inc(RCU_DYNTICKS_IDX); + } + + return ret; +} + +static __always_inline void warn_rcu_exit(bool rcu) +{ + if (rcu) + ct_state_inc(RCU_DYNTICKS_IDX); + preempt_enable_notrace(); +} + #else static inline void ct_idle_enter(void) { } static inline void ct_idle_exit(void) { } + +static __always_inline bool warn_rcu_enter(void) { return false; } +static __always_inline void warn_rcu_exit(bool rcu) { } #endif /* !CONFIG_CONTEXT_TRACKING_IDLE */ =20 #endif diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index e3375bc..50d4863 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -55,6 +55,7 @@ #include #include #include +#include =20 #include =20 @@ -6555,6 +6556,7 @@ void lockdep_rcu_suspicious(const char *file, const i= nt line, const char *s) { struct task_struct *curr =3D current; int dl =3D READ_ONCE(debug_locks); + bool rcu =3D warn_rcu_enter(); =20 /* Note: the following can be executed concurrently, so be careful. */ pr_warn("\n"); @@ -6595,5 +6597,6 @@ void lockdep_rcu_suspicious(const char *file, const i= nt line, const char *s) lockdep_print_held_locks(curr); pr_warn("\nstack backtrace:\n"); dump_stack(); + warn_rcu_exit(rcu); } EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious); diff --git a/kernel/panic.c b/kernel/panic.c index 463c929..487f5b0 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -34,6 +34,7 @@ #include #include #include +#include #include #include =20 @@ -679,6 +680,7 @@ void __warn(const char *file, int line, void *caller, u= nsigned taint, void warn_slowpath_fmt(const char *file, int line, unsigned taint, const char *fmt, ...) { + bool rcu =3D warn_rcu_enter(); struct warn_args args; =20 pr_warn(CUT_HERE); @@ -693,11 +695,13 @@ void warn_slowpath_fmt(const char *file, int line, un= signed taint, va_start(args.args, fmt); __warn(file, line, __builtin_return_address(0), taint, NULL, &args); va_end(args.args); + warn_rcu_exit(rcu); } EXPORT_SYMBOL(warn_slowpath_fmt); #else void __warn_printk(const char *fmt, ...) { + bool rcu =3D warn_rcu_enter(); va_list args; =20 pr_warn(CUT_HERE); @@ -705,6 +709,7 @@ void __warn_printk(const char *fmt, ...) va_start(args, fmt); vprintk(fmt, args); va_end(args); + warn_rcu_exit(rcu); } EXPORT_SYMBOL(__warn_printk); #endif diff --git a/lib/bug.c b/lib/bug.c index c223a25..e0ff219 100644 --- a/lib/bug.c +++ b/lib/bug.c @@ -47,6 +47,7 @@ #include #include #include +#include =20 extern struct bug_entry __start___bug_table[], __stop___bug_table[]; =20 @@ -153,7 +154,7 @@ struct bug_entry *find_bug(unsigned long bugaddr) return module_find_bug(bugaddr); } =20 -enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) +static enum bug_trap_type __report_bug(unsigned long bugaddr, struct pt_re= gs *regs) { struct bug_entry *bug; const char *file; @@ -209,6 +210,18 @@ enum bug_trap_type report_bug(unsigned long bugaddr, s= truct pt_regs *regs) return BUG_TRAP_TYPE_BUG; } =20 +enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) +{ + enum bug_trap_type ret; + bool rcu =3D false; + + rcu =3D warn_rcu_enter(); + ret =3D __report_bug(bugaddr, regs); + warn_rcu_exit(rcu); + + return ret; +} + static void clear_once_table(struct bug_entry *start, struct bug_entry *en= d) { struct bug_entry *bug;