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bh=0Bbvo5JM5EzDceFV5HFBn3Tn1Nvzi+vQVAFu4wTmlqI=; b=u81cA4nqP3SwSZYYHDPT/c5iJMa/mvGsUCdVoLwzxrcGgMFdrtexAyfBe4goeV8CnoZjmp Y8QnIl1s+PhdvBc1uZ67SH+P2UaPM0wBkVnrC+24JdQDekZnjHXK0r1hvcI9G8U6J7NYb0 GCCAq5M8x3jgV7eAiA8AiD6S1s+UCp9bvRP16OM6cb3/Jyv5mOV/wewYycedofExfwcFoI B/bCmIOP2cc3iImIeld1Rds/k5ogd28dgZPxvk8gfIb2Kql+LxMpp37/g8R0ra44dqB2oq 9FxmU2xf61PGf8Ow4QVc3bBeLX5rbaVXjqV/rrIUGLiFyYarvXjg33CZOAHzgQ== From: Eugene Mavick Date: Sat, 01 Aug 2026 18:59:41 +0800 Subject: [PATCH v4 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: <20260801-refcount-final-put-trace-v4-1-2e58678f0ffd@mavick.dev> References: <20260801-refcount-final-put-trace-v4-0-2e58678f0ffd@mavick.dev> In-Reply-To: <20260801-refcount-final-put-trace-v4-0-2e58678f0ffd@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=4872; i=m@mavick.dev; h=from:subject:message-id; bh=ll6nYQOrO2XWydxLfhKt+/rvzaAqc+x2/e8etpbuoBQ=; b=owGbwMvMwCU2V/5U3e1aE3/G02pJDFm5FzdGbl2SrP/R6MkG6f0mqz+8/KArc/GXXJBuwnVnm 8LVi1U2dZSyMIhxMciKKbLUZCW4Z6yclWh8dFIPzBxWJpAhDFycAjCRnGWMDHdzXrOYP4isqmRz VKud4Pf8y/2zOpe+ZH+4tbBw2o2QC16MDA/PHJbIWcL2r+Ttg51bNy/dYv5h9/yWhML3E88wfKt XfsAKAA== X-Developer-Key: i=m@mavick.dev; a=openpgp; fpr=7C6A604768A99A6133C5928C9D1FCA7EDB7D344F X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: D79A2100002 X-Stat-Signature: eebyru7aqa3rpcbfz1twkajoam4z9jk5 X-HE-Tag: 1785582045-950015 X-HE-Meta: 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 DHnGwMFs frNIwupEa9i/vNFubxDxQuJxx9wMf2xqEpbh9SaOb54pUhD/0BGNAfOgcn9XeDd1RpdGnUzzS5ANyhdkbz+KCe3ecv9XIJILPC+hAZ5FbSuzbZPQUW5cmtxxAalIHOi+aQ4lICJfrY/wSxrNJtlX+WaFtKjFWVSvYWFpYxOH4Il8v+DqDOIOmtkYk7OuBiTiqXhy4stne89P6uIJUXvbhrmihiyVLHnjxkQFGl+UKWP/ePKF5kXI43ejFIRz5S436w1SaU1LbeReX8Y6VwJQjd6ZBQPxwu3psFIWoUiD9wvra2B+6gUvAMzCBbKZfa9XFdgA29kz7+cqkqVA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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) - ip: return address of trace wrapper macro call - obj: refcount object(struct percpu_ref, refcount_t) Signed-off-by: Eugene Mavick --- include/linux/ref_trace.h | 40 +++++++++++++++++++++++++++++++ include/trace/events/ref_trace.h | 51 ++++++++++++++++++++++++++++++++++++++++ lib/Makefile | 2 ++ lib/ref_trace.c | 13 ++++++++++ 4 files changed, 106 insertions(+) diff --git a/include/linux/ref_trace.h b/include/linux/ref_trace.h new file mode 100644 index 000000000000..c93c30bc20d2 --- /dev/null +++ b/include/linux/ref_trace.h @@ -0,0 +1,40 @@ +/* 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, unsigned long ip, 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_, _THIS_IP_, obj); \ + } while (0) + +#define do_trace_ref_final_put_cond(cond, obj) \ + do { \ + if (tracepoint_enabled(ref_trace_final_put)) { \ + if (cond) \ + do_ref_trace_final_put(_RET_IP_, _THIS_IP_, obj);\ + } \ + } while (0) + +#else /* !CONFIG_TRACEPOINTS */ +static inline void do_ref_trace_final_put( + unsigned long caller, + unsigned long ip, + const void *obj) +{ +} +#define do_trace_ref_final_put(obj) do { } while (0) +#define do_trace_ref_final_put_cond(cond, 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..8bd9aa30a540 --- /dev/null +++ b/include/trace/events/ref_trace.h @@ -0,0 +1,51 @@ +/* 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: return address of refcount + * function(refcount_sub_and_test, percpu_ref_put_many) + * @ip: return address of trace wrapper macro call, + * inlining may cause it to be something else tho + * @obj: refcount object(struct percpu_ref, refcount_t) + * + * Tracepoint instrumentation can be added using the do_ref_trace_final_put + * macro defined in include/linux/ref_trace.h + * which uses _RET_IP_ and _THIS_IP_ for caller and ip arguments respectively, + * thus only requiring obj arg to be supplied + */ +TRACE_EVENT(ref_trace_final_put, + + TP_PROTO(unsigned long caller, unsigned long ip, const void *obj), + + TP_ARGS(caller, ip, obj), + + TP_STRUCT__entry( + __field( unsigned long, caller ) + __field( unsigned long, ip ) + __field( const void *, obj ) + ), + + TP_fast_assign( + __entry->caller = caller; + __entry->ip = ip; + __entry->obj = obj; + ), + + TP_printk("caller=%pS ip=%pS obj=%p", + (void *)__entry->caller, + (void *)__entry->ip, + __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..22fe372f468f --- /dev/null +++ b/lib/ref_trace.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 +#define CREATE_TRACE_POINTS +#include +#include + +//Wrapper function for functions defined entirely in header files +void do_ref_trace_final_put(unsigned long caller, unsigned long ip, const void *obj) +{ + trace_call__ref_trace_final_put(caller, ip, obj); +} +EXPORT_SYMBOL_GPL(do_ref_trace_final_put); + +EXPORT_TRACEPOINT_SYMBOL_GPL(ref_trace_final_put); -- 2.51.2