From nobody Thu Apr 2 05:53:17 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 63F543B6363; Mon, 30 Mar 2026 12:50:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774875030; cv=none; b=q2VDXF1kXLKX83NxY45o7/HphMhEdsamdgChADaOts1f75dy+v4ahLvN2mwDFEyPmQOXL3JVaYpPNe7DMvp47c/8FokeKxo3cAF757crsnYhYbyGctp8Uh78E3fhPPAJDsE7fWMd0KFKGOiUlDixSlPBEKVU+4ZDsaWqMefUP5M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774875030; c=relaxed/simple; bh=EXYO15ATJn+QqnvNAAHVALJL+AFONrSWh1pbmJzee9o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=iD6KP1D3RIdoPEF5VOmhy6AH6fXxSMKVUn16xd0GFjOBgCxohvkGwCrlCb6y1PlRfa4EKG2rPM0IysnKl0+lsvSaQmjRlUjIa1f2RiNHoHrYvBGHEOj4TCQsnarl90AwGwuC/Qdi6H6wAShsGXIgvSV3Z+RNbq/WDRMHCbogdic= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oWNiD1YG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oWNiD1YG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 440A5C4CEF7; Mon, 30 Mar 2026 12:50:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774875030; bh=EXYO15ATJn+QqnvNAAHVALJL+AFONrSWh1pbmJzee9o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oWNiD1YGMRMaVNKZnSv6Rnw8An31861K2yca6enH8C0C7F8MwXqsfjCk0V3qWnZzi vVtfd0Egu4RHzPz6bzY61WDj5iejYiBNmWVrbcInufMx4tc3abYI5Uxp3N+faVJBWI MHGlI/MOteQSLkRau0JfOGwE2re/ACTY+XSDXDm5CrCHwftSosh+wD6BspVGSxhxBN aHz/gW2lgkBanax+1DUffvWKU5gp7p/C7gPsDiCAUhanR92mcccBLW32w9/eTQjnVk tWhf14RdAnntUBYqvhzm2ZLgdYF509C55ri/LnZzYcLmbLh1RQC/l0xoAODEnI70pu 8VB2wm5nZdp1A== From: "Masami Hiramatsu (Google)" To: Steven Rostedt Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Ian Rogers Subject: [PATCH v14 5/5] ring-buffer: Add persistent ring buffer selftest Date: Mon, 30 Mar 2026 21:50:27 +0900 Message-ID: <177487502763.3463592.7901517545360137050.stgit@mhiramat.tok.corp.google.com> X-Mailer: git-send-email 2.53.0.1018.g2bb0e51243-goog In-Reply-To: <177487498530.3463592.12715592581212799257.stgit@mhiramat.tok.corp.google.com> References: <177487498530.3463592.12715592581212799257.stgit@mhiramat.tok.corp.google.com> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: Masami Hiramatsu (Google) Add a self-destractive test for the persistent ring buffer. This will invalidate some sub-buffer pages in the persistent ring buffer when kernel gets panic, and check whether the number of detected invalid pages and the total entry_bytes are the same as record after reboot. This can ensure the kernel correctly recover partially corrupted persistent ring buffer when boot. The test only runs on the persistent ring buffer whose name is "ptracingtest". And user has to fill it up with events before kernel panics. To run the test, enable CONFIG_RING_BUFFER_PERSISTENT_INJECT and you have to setup the kernel cmdline; reserve_mem=3D20M:2M:trace trace_instance=3Dptracingtest^traceoff@trace panic=3D1 And run following commands after the 1st boot; cd /sys/kernel/tracing/instances/ptracingtest echo 1 > tracing_on echo 1 > events/enable sleep 3 echo c > /proc/sysrq-trigger After panic message, the kernel will reboot and run the verification on the persistent ring buffer, e.g. Ring buffer meta [2] invalid buffer page detected Ring buffer meta [2] is from previous boot! (318 pages discarded) Ring buffer testing [2] invalid pages: PASSED (318/318) Ring buffer testing [2] entry_bytes: PASSED (1300476/1300476) Signed-off-by: Masami Hiramatsu (Google) --- Changes in v14: - Rename config to CONFIG_RING_BUFFER_PERSISTENT_INJECT. - Clear meta->nr_invalid/entry_bytes after testing. - Add test commands in config comment. Changes in v10: - Add entry_bytes test. - Do not compile test code if CONFIG_RING_BUFFER_PERSISTENT_SELFTEST=3Dn. Changes in v9: - Test also reader pages. --- include/linux/ring_buffer.h | 1 + kernel/trace/Kconfig | 31 +++++++++++++++++++ kernel/trace/ring_buffer.c | 71 +++++++++++++++++++++++++++++++++++++++= ++++ kernel/trace/trace.c | 4 ++ 4 files changed, 107 insertions(+) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 994f52b34344..0670742b2d60 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -238,6 +238,7 @@ int ring_buffer_subbuf_size_get(struct trace_buffer *bu= ffer); =20 enum ring_buffer_flags { RB_FL_OVERWRITE =3D 1 << 0, + RB_FL_TESTING =3D 1 << 1, }; =20 #ifdef CONFIG_RING_BUFFER diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index e130da35808f..07305ed6d745 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -1202,6 +1202,37 @@ config RING_BUFFER_VALIDATE_TIME_DELTAS Only say Y if you understand what this does, and you still want it enabled. Otherwise say N =20 +config RING_BUFFER_PERSISTENT_INJECT + bool "Enable persistent ring buffer error injection test" + depends on RING_BUFFER + help + Run a selftest on the persistent ring buffer which names + "ptracingtest" (and its backup) when panic_on_reboot by + invalidating ring buffer pages. + To use this, boot kernel with "ptracingtest" persistent + ring buffer, e.g. + + reserve_mem=3D20M:2M:trace trace_instance=3Dptracingtest@trace panic= =3D1 + + And after the 1st boot, run test command, like; + + cd /sys/kernel/tracing/instances/ptracingtest + echo 1 > events/enable + echo 1 > tracing_on + sleep 3 + echo c > /proc/sysrq-trigger + + After panic message, the kernel reboots and show test results + on the boot log. + + Note that user has to enable events on the persistent ring + buffer manually to fill up ring buffers before rebooting. + Since this invalidates the data on test target ring buffer, + "ptracingtest" persistent ring buffer must not be used for + actual tracing, but only for testing. + + If unsure, say N + config MMIOTRACE_TEST tristate "Test module for mmiotrace" depends on MMIOTRACE && m diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 5049cf13021e..7f8140c54fce 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -64,6 +64,10 @@ struct ring_buffer_cpu_meta { unsigned long commit_buffer; __u32 subbuf_size; __u32 nr_subbufs; +#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT + __u32 nr_invalid; + __u32 entry_bytes; +#endif int buffers[]; }; =20 @@ -2078,6 +2082,21 @@ static void rb_meta_validate_events(struct ring_buff= er_per_cpu *cpu_buffer) =20 pr_info("Ring buffer meta [%d] is from previous boot! (%d pages discarded= )\n", cpu_buffer->cpu, discarded); + +#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT + if (meta->nr_invalid) + pr_info("Ring buffer testing [%d] invalid pages: %s (%d/%d)\n", + cpu_buffer->cpu, + (discarded =3D=3D meta->nr_invalid) ? "PASSED" : "FAILED", + discarded, meta->nr_invalid); + if (meta->entry_bytes) + pr_info("Ring buffer testing [%d] entry_bytes: %s (%ld/%ld)\n", + cpu_buffer->cpu, + (entry_bytes =3D=3D meta->entry_bytes) ? "PASSED" : "FAILED", + (long)entry_bytes, (long)meta->entry_bytes); + meta->nr_invalid =3D 0; + meta->entry_bytes =3D 0; +#endif return; =20 invalid: @@ -2558,12 +2577,64 @@ static void rb_free_cpu_buffer(struct ring_buffer_p= er_cpu *cpu_buffer) kfree(cpu_buffer); } =20 +#ifdef CONFIG_RING_BUFFER_PERSISTENT_INJECT +static void rb_test_inject_invalid_pages(struct trace_buffer *buffer) +{ + struct ring_buffer_per_cpu *cpu_buffer; + struct ring_buffer_cpu_meta *meta; + struct buffer_data_page *dpage; + u32 entry_bytes =3D 0; + unsigned long ptr; + int subbuf_size; + int invalid =3D 0; + int cpu; + int i; + + if (!(buffer->flags & RB_FL_TESTING)) + return; + + guard(preempt)(); + cpu =3D smp_processor_id(); + + cpu_buffer =3D buffer->buffers[cpu]; + meta =3D cpu_buffer->ring_meta; + ptr =3D (unsigned long)rb_subbufs_from_meta(meta); + subbuf_size =3D meta->subbuf_size; + + for (i =3D 0; i < meta->nr_subbufs; i++) { + int idx =3D meta->buffers[i]; + + dpage =3D (void *)(ptr + idx * subbuf_size); + /* Skip unused pages */ + if (!local_read(&dpage->commit)) + continue; + + /* Invalidate even pages. */ + if (!(i & 0x1)) { + local_add(subbuf_size + 1, &dpage->commit); + invalid++; + } else { + /* Count total commit bytes. */ + entry_bytes +=3D local_read(&dpage->commit); + } + } + + pr_info("Inject invalidated %d pages on CPU%d, total size: %ld\n", + invalid, cpu, (long)entry_bytes); + meta->nr_invalid =3D invalid; + meta->entry_bytes =3D entry_bytes; +} +#else /* !CONFIG_RING_BUFFER_PERSISTENT_INJECT */ +#define rb_test_inject_invalid_pages(buffer) do { } while (0) +#endif + /* Stop recording on a persistent buffer and flush cache if needed. */ static int rb_flush_buffer_cb(struct notifier_block *nb, unsigned long eve= nt, void *data) { struct trace_buffer *buffer =3D container_of(nb, struct trace_buffer, flu= sh_nb); =20 ring_buffer_record_off(buffer); + rb_test_inject_invalid_pages(buffer); arch_ring_buffer_flush_range(buffer->range_addr_start, buffer->range_addr= _end); return NOTIFY_DONE; } diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 4189ec9df6a5..108b0d16badf 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9366,6 +9366,8 @@ static void setup_trace_scratch(struct trace_array *t= r, memset(tscratch, 0, size); } =20 +#define TRACE_TEST_PTRACING_NAME "ptracingtest" + static int allocate_trace_buffer(struct trace_array *tr, struct array_buffer *buf, un= signed long size) { @@ -9378,6 +9380,8 @@ allocate_trace_buffer(struct trace_array *tr, struct = array_buffer *buf, unsigned buf->tr =3D tr; =20 if (tr->range_addr_start && tr->range_addr_size) { + if (!strcmp(tr->name, TRACE_TEST_PTRACING_NAME)) + rb_flags |=3D RB_FL_TESTING; /* Add scratch buffer to handle 128 modules */ buf->buffer =3D ring_buffer_alloc_range(size, rb_flags, 0, tr->range_addr_start,