From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-y-209.mailbox.org (mout-y-209.mailbox.org [91.198.250.237]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F25783E9F76; Mon, 6 Jul 2026 06:43:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.198.250.237 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783320220; cv=none; b=i9pC3yrwauay+96TPBgCWYlUFsOpa6T3iWO4pT5snxOuNuQKHv8A0VB/iVdK6bnVO9kEL9nLLcoAypwtfv8hciD13zlsoHgBl4HIvNA/M4lUP0W5dvKh03lknd3P3H4vjbcmdM+MIwS28zyh9mLRILNvZ/2IL9xIDvTv2hFMB4Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783320220; c=relaxed/simple; bh=qHwnbzvpK9wYBzbeGmnuCtzzLwF8aY1zM3ldVu/OfqE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=mA2aZKp5WISH26TdBGGrJaMmM+fmzaTZrfJhXaW11GhFcP6DQm0aLFy9tu//qH1z2tVjBKUclPcj6VzQXeS9bfir5Ge5C2pt5C6PY61yB7YPRUYC0QzdvGYOgTr2C+VlCUwHEWgvouu1brqkPAZLorsiI01s/TvfWmHdszCnpo4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mavick.dev; spf=pass smtp.mailfrom=mavick.dev; arc=none smtp.client-ip=91.198.250.237 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=mavick.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mavick.dev Received: from smtp1.mailbox.org (smtp1.mailbox.org [10.196.197.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (4096 bits) server-digest SHA512) (No client certificate requested) by mout-y-209.mailbox.org (Postfix) with ESMTPS id 4gt7r03qBCz7vTv; Sun, 05 Jul 2026 02:37:52 +0200 (CEST) From: Eugene Mavick Date: Sun, 05 Jul 2026 08:36:56 +0800 Subject: [PATCH 1/4] tracing: add ref_trace_final_put tracepoint Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260705-refcount-final-put-trace-v1-1-a41d3fd0e869@mavick.dev> References: <20260705-refcount-final-put-trace-v1-0-a41d3fd0e869@mavick.dev> In-Reply-To: <20260705-refcount-final-put-trace-v1-0-a41d3fd0e869@mavick.dev> To: Will Deacon , Peter Zijlstra , Boqun Feng , Mark Rutland , Gary Guo , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, Eugene Mavick X-Developer-Signature: v=1; a=openpgp-sha256; l=4836; i=m@mavick.dev; h=from:subject:message-id; bh=qHwnbzvpK9wYBzbeGmnuCtzzLwF8aY1zM3ldVu/OfqE=; b=owGbwMvMwCU2V/5U3e1aE3/G02pJDFmey20tX0Uv+uo9wcO1T/IDF/s+XU9nj3XtiUxM00Jnn 2Bi49neUcrCIMbFICumyFKTleCesXJWovHRST0wc1iZQIYwcHEKwETWVTL8T2+7m3q0rGDbIYVf tlNavGeYX9rGcrNgn13McuubTG885Bj+Z4t5HgmRc08+Wnty8xrdb2GHFuzybQq7eF59bYOWdoM mIwA= X-Developer-Key: i=m@mavick.dev; a=openpgp; fpr=7C6A604768A99A6133C5928C9D1FCA7EDB7D344F Add ref_trace_final_put tracepoint and related core infrastructure ref_trace_final_put fires when a reference count reaches zero and the object enters its final release path. The tracepoint records three fields: - caller: function that called the refcounting function(refcount_sub_and_test, percpu_ref_put_many) - fn: refcounting function(eg refcount_sub_and_test) - obj: refcount object(struct percpu_ref, refcount_t) Signed-off-by: Eugene Mavick --- MAINTAINERS | 2 ++ include/linux/ref_trace.h | 26 +++++++++++++++++++++++ include/trace/events/ref_trace.h | 46 ++++++++++++++++++++++++++++++++++++++++ lib/Makefile | 2 ++ lib/ref_trace.c | 12 +++++++++++ 5 files changed, 88 insertions(+) diff --git a/MAINTAINERS b/MAINTAINERS index 10e8253181d3..8dab37726b9d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4210,7 +4210,9 @@ S: Maintained F: Documentation/atomic_*.txt F: arch/*/include/asm/atomic*.h F: include/*/atomic*.h +F: include/linux/ref_trace.h F: include/linux/refcount.h +F: lib/ref_trace.h F: scripts/atomic/ F: rust/kernel/sync/atomic.rs F: rust/kernel/sync/atomic/ diff --git a/include/linux/ref_trace.h b/include/linux/ref_trace.h new file mode 100644 index 000000000000..54e9fba9e3e9 --- /dev/null +++ b/include/linux/ref_trace.h @@ -0,0 +1,26 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_REF_TRACE_H +#define _LINUX_REF_TRACE_H + +#include +#include + +/* Declare the tracepoint so tracepoint_enabled() can be used */ +DECLARE_TRACEPOINT(ref_trace_final_put); + +#ifdef CONFIG_TRACEPOINTS +/* Wrapper function implemented in lib/ref_trace.c */ +extern void do_ref_trace_final_put(unsigned long caller, const char *fn, const void *obj); + +#define trace_ref_final_put(obj) \ + do { \ + if (tracepoint_enabled(ref_trace_final_put)) \ + do_ref_trace_final_put(_RET_IP_, __func__, obj); \ + } while (0) + +#else /* !CONFIG_TRACEPOINTS */ +static inline void do_ref_trace_final_put(unsigned long caller, const char *fn, const void *obj) { } +#define trace_ref_final_put(obj) do { } while (0) +#endif + +#endif /* _LINUX_REF_TRACE_H */ diff --git a/include/trace/events/ref_trace.h b/include/trace/events/ref_trace.h new file mode 100644 index 000000000000..e6037a325be2 --- /dev/null +++ b/include/trace/events/ref_trace.h @@ -0,0 +1,46 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM ref_trace + +#if !defined(_TRACE_REF_TRACE_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_REF_TRACE_H + +#include + +/** + * ref_trace_final_put - trace when a reference count reaches zero + * @caller: function that called the refcounting + * function(refcount_sub_and_test, percpu_ref_put_many) + * @fn: refcounting function(eg refcount_sub_and_test) + * @obj: refcount object(struct percpu_ref, refcount_t) + * + * Tracepoint instrumentation can be added using the ref_trace_final_put + * macro defined in include/linux/ref_trace.h + * which uses _RET_IP_ and __func__ for caller and fn arguments respectively, + * thus only requiring obj arg to be supplied + */ +TRACE_EVENT(ref_trace_final_put, + + TP_PROTO(unsigned long caller, const char *fn, const void *obj), + + TP_ARGS(caller, fn, obj), + + TP_STRUCT__entry( + __field(unsigned long, caller) + __string(fn, fn) + __field(const void *, obj) + ), + + TP_fast_assign( + __entry->caller = caller; + __assign_str(fn); + __entry->obj = obj; + ), + + TP_printk("caller=%pS fn=%s obj=%p", (void *)__entry->caller, __get_str(fn), __entry->obj) +); + +#endif /* _TRACE_REF_TRACE_H */ + +/* This part must be outside protection */ +#include diff --git a/lib/Makefile b/lib/Makefile index f33a24bf1c19..41737090a95d 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -335,3 +335,5 @@ CONTEXT_ANALYSIS_test_context-analysis.o := y obj-$(CONFIG_CONTEXT_ANALYSIS_TEST) += test_context-analysis.o subdir-$(CONFIG_FORTIFY_SOURCE) += test_fortify + +obj-$(CONFIG_TRACEPOINTS) += ref_trace.o diff --git a/lib/ref_trace.c b/lib/ref_trace.c new file mode 100644 index 000000000000..25f7c17c7c47 --- /dev/null +++ b/lib/ref_trace.c @@ -0,0 +1,12 @@ +// SPDX-License-Identifier: GPL-2.0 +#define CREATE_TRACE_POINTS +#include + +//Wrapper function for functions defined entirely in header files +void do_ref_trace_final_put(unsigned long caller, const char *fn, const void *obj) +{ + trace_ref_trace_final_put(caller, fn, obj); +} +EXPORT_SYMBOL_GPL(do_ref_trace_final_put); + +EXPORT_TRACEPOINT_SYMBOL_GPL(ref_trace_final_put); -- 2.51.2