From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eugene Mavick Date: Fri, 10 Jul 2026 13:30:39 +0800 Subject: [PATCH v2 1/5] tracing: add ref_trace_final_put tracepoint MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260710-refcount-final-put-trace-v2-1-557cfce860a2@mavick.dev> References: <20260710-refcount-final-put-trace-v2-0-557cfce860a2@mavick.dev> In-Reply-To: <20260710-refcount-final-put-trace-v2-0-557cfce860a2@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-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=4782; i=m@mavick.dev; h=from:subject:message-id; bh=qR1tr9zkvfO0Ekv8EXksBaXJupN2DKoOXEp8ReORpQI=; b=owGbwMvMwCU2V/5U3e1aE3/G02pJDFkBzT0KGade/c9KdFHS3h8rXtH3ZPqyLVL5tiWiZ997v /MXTEjsKGVhEONikBVTZKnJSnDPWDkr0fjopB6YOaxMIEMYuDgFYCJvtzL8z0vLdXzxyiZUwe4R x0+dqs6sZO7uVRfrkp6uPSuhM9t4G8P/0kO8PGqhJzoeq/yr6Zf+scT6y67vgcwLzlpFrnlt3qL CCwA= X-Developer-Key: i=m@mavick.dev; a=openpgp; fpr=7C6A604768A99A6133C5928C9D1FCA7EDB7D344F X-Endpoint-Received: by B4 Relay for m@mavick.dev/default with auth_id=850 List-Id: B4 Relay Submissions 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 --- v2: -change trace_ref_final_put macro name to do_trace_ref_final_put to avoid overlap with tracepoint names(trace_*) -change, in above mentioned macro, from trace_ref_trace_final_put( to trace_call__ref_trace_final_put( to avoid double check -changes suggested by Steven Rostedt -v1:https://lore.kernel.org/all/20260705-refcount-final-put-trace-v1-1-cdd0014626a9@mavick.dev/ --- include/linux/ref_trace.h | 26 +++++++++++++++++++++++ include/trace/events/ref_trace.h | 46 ++++++++++++++++++++++++++++++++++++++++ lib/Makefile | 2 ++ lib/ref_trace.c | 12 +++++++++++ 4 files changed, 86 insertions(+) diff --git a/include/linux/ref_trace.h b/include/linux/ref_trace.h new file mode 100644 index 000000000000..6c6600938a47 --- /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 do_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 do_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..9102dc7117db --- /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_call__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