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Mon, 13 Oct 2025 23:55:46 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFFlbUjRO9R/NpxxXldayXIglwjuXec+Uez9hxiwOvKHT+csT8ueG+UPjaUZgLVeIy5qL+RIQ== X-Received: by 2002:a05:600c:8b6a:b0:46f:b42e:ed88 with SMTP id 5b1f17b1804b1-46fb42eee4fmr122418765e9.41.1760424945788; Mon, 13 Oct 2025 23:55:45 -0700 (PDT) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([185.107.56.42]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fab4e22d8sm142757855e9.5.2025.10.13.23.55.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Oct 2025 23:55:45 -0700 (PDT) Message-ID: <1a0d9a427b36d4bcff992dfb8694436cd24d6af3.camel@redhat.com> Subject: Re: [PATCH 3/3] rv: Add explicit lockdep context for reactors From: Gabriele Monaco To: Thomas =?ISO-8859-1?Q?Wei=DFschuh?= , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Nam Cao Cc: linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 14 Oct 2025 08:55:44 +0200 In-Reply-To: <20251014-rv-lockdep-v1-3-0b9e51919ea8@linutronix.de> References: <20251014-rv-lockdep-v1-0-0b9e51919ea8@linutronix.de> <20251014-rv-lockdep-v1-3-0b9e51919ea8@linutronix.de> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-10-14 at 07:51 +0200, Thomas Wei=C3=9Fschuh wrote: > Reactors can be called from any context through tracepoints. > When developing reactors care needs to be taken to only call APIs which > are safe. As the tracepoints used during testing may not actually be > called from restrictive contexts lockdep may not be helpful. >=20 > Add explicit overrides to help lockdep find invalid code patterns. >=20 > The usage of LD_WAIT_FREE will trigger lockdep warnings in the panic > reactor. These are indeed valid warnings but they are out of scope for > RV and will instead be fixed by the printk subsystem. Looks like a nice addition! If I get it correctly, this patch does trigger a lockdep warning with the current state of the kernel. Is there a plan of fixing the warning in print= k? I assume this series would need to wait for that or did you have other idea= s? Thanks, Gabriele >=20 > Signed-off-by: Thomas Wei=C3=9Fschuh > --- > =C2=A0kernel/trace/rv/rv_reactors.c | 4 ++++ > =C2=A01 file changed, 4 insertions(+) >=20 > diff --git a/kernel/trace/rv/rv_reactors.c b/kernel/trace/rv/rv_reactors.= c > index > 8c02426bc3bd944265f809e431283d1a20d56a8c..d9d335ae9badaa320f1d35dd159a033= c3a30 > eb1a 100644 > --- a/kernel/trace/rv/rv_reactors.c > +++ b/kernel/trace/rv/rv_reactors.c > @@ -61,6 +61,7 @@ > =C2=A0 *=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 printk > =C2=A0 */ > =C2=A0 > +#include > =C2=A0#include > =C2=A0 > =C2=A0#include "rv.h" > @@ -480,6 +481,7 @@ int init_rv_reactors(struct dentry *root_dir) > =C2=A0 > =C2=A0void rv_react(struct rv_monitor *monitor, const char *msg, ...) > =C2=A0{ > + static DEFINE_WAIT_OVERRIDE_MAP(rv_react_map, LD_WAIT_FREE); > =C2=A0 va_list args; > =C2=A0 > =C2=A0 if (!rv_reacting_on() || !monitor->react) > @@ -487,7 +489,9 @@ void rv_react(struct rv_monitor *monitor, const char = *msg, > ...) > =C2=A0 > =C2=A0 va_start(args, msg); > =C2=A0 > + lock_map_acquire_try(&rv_react_map); > =C2=A0 monitor->react(msg, args); > + lock_map_release(&rv_react_map); > =C2=A0 > =C2=A0 va_end(args); > =C2=A0}