From nobody Thu Apr 9 14:56:42 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 85DA026B764; Sat, 7 Mar 2026 14:26:33 +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=1772893593; cv=none; b=kz4dHfpQfzwf31BZZEiZ+HVmaVJZxZiLzjrQi2lM8P6SALXqS83n3YRc6kfXc1+uUrM3UcpdPcBydkUOJ2ykvWICLSwRoSyq00LqJra0FHxTb14yhxyEAf1RsgHLLqGsXHHNcKP/vfMJVej/SoVu5QZUZLy3FkgQEfM62VXOUHA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772893593; c=relaxed/simple; bh=M1az3QXMLWgrtDJwC74p4p6tdmkG/ib+b/Gi5V26mvg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=tG+dJvcBdxHQGroDko375bLlGOWFqhew/G6CZ6kco6gLkqiKMZWQ2pa9RaDvJwq/xFnfqGbVcpOYxL/1e4o6JRCxmwEDIESYcHEpV5X9C46cpLjwZH1Ho2Glz6M7bHVwjQxRuQ8hlO+EL8LXLIpLg2RBdw90KxoqPxFiByd57B4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ubj5pYlp; 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="Ubj5pYlp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33A46C19422; Sat, 7 Mar 2026 14:26:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772893593; bh=M1az3QXMLWgrtDJwC74p4p6tdmkG/ib+b/Gi5V26mvg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ubj5pYlppzpheISh4cn34NoRwXAtTOjv6qRgBur+/FmWh5hMZgn6RElQlm1MWfOe3 HxTPW90D0evc7cbN+7Gu6nrG8OnWvcG2JIUmDe0v6a6TylJLMJK/HBrfRae/DNnULS 7qi0hxCFqUq+GWEejcqPuD8o1ieqsLEDYoRRXOQQSjbjEos3DWvV2/7NV8j+pp6x5p nxqdZMb2nC2+vnjkIFsdy/ZaRuqaIhcEOofPWNWr13nRZH9dVE5FZEVv9G1hRDdk7U IIO2YXaineMt7CxH2H3FQ4JTw2+cdC3eX3AqRtdvtALPIBpoe3xD0gPpKUPRjEZBOp t6jat23eVirTg== From: "Masami Hiramatsu (Google)" To: Steven Rostedt Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH v7 1/2] ring-buffer: Flush and stop persistent ring buffer on panic Date: Sat, 7 Mar 2026 23:26:30 +0900 Message-ID: <177289358988.248514.6404820659978599337.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <177289358078.248514.14947007976699929481.stgit@devnote2> References: <177289358078.248514.14947007976699929481.stgit@devnote2> 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) On real hardware, panic and machine reboot may not flush hardware cache to memory. This means the persistent ring buffer, which relies on a coherent state of memory, may not have its events written to the buffer and they may be lost. Moreover, there may be inconsistency with the counters which are used for validation of the integrity of the persistent ring buffer which may cause all data to be discarded. To avoid this issue, stop recording of the ring buffer on panic and flush the cache of the ring buffer's memory. Fixes: e645535a954a ("tracing: Add option to use memmapped memory for trace= boot instance") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) --- arch/alpha/include/asm/Kbuild | 1 + arch/arc/include/asm/Kbuild | 1 + arch/arm/include/asm/Kbuild | 1 + arch/arm64/include/asm/ring_buffer.h | 10 ++++++++++ arch/csky/include/asm/Kbuild | 1 + arch/hexagon/include/asm/Kbuild | 1 + arch/loongarch/include/asm/Kbuild | 1 + arch/m68k/include/asm/Kbuild | 1 + arch/microblaze/include/asm/Kbuild | 1 + arch/mips/include/asm/Kbuild | 1 + arch/nios2/include/asm/Kbuild | 1 + arch/openrisc/include/asm/Kbuild | 1 + arch/parisc/include/asm/Kbuild | 1 + arch/powerpc/include/asm/Kbuild | 1 + arch/riscv/include/asm/Kbuild | 1 + arch/s390/include/asm/Kbuild | 1 + arch/sh/include/asm/Kbuild | 1 + arch/sparc/include/asm/Kbuild | 1 + arch/um/include/asm/Kbuild | 1 + arch/x86/include/asm/Kbuild | 1 + arch/xtensa/include/asm/Kbuild | 1 + include/asm-generic/ring_buffer.h | 13 +++++++++++++ kernel/trace/ring_buffer.c | 22 ++++++++++++++++++++++ 23 files changed, 65 insertions(+) create mode 100644 arch/arm64/include/asm/ring_buffer.h create mode 100644 include/asm-generic/ring_buffer.h diff --git a/arch/alpha/include/asm/Kbuild b/arch/alpha/include/asm/Kbuild index 483965c5a4de..b154b4e3dfa8 100644 --- a/arch/alpha/include/asm/Kbuild +++ b/arch/alpha/include/asm/Kbuild @@ -5,4 +5,5 @@ generic-y +=3D agp.h generic-y +=3D asm-offsets.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D text-patching.h diff --git a/arch/arc/include/asm/Kbuild b/arch/arc/include/asm/Kbuild index 4c69522e0328..483caacc6988 100644 --- a/arch/arc/include/asm/Kbuild +++ b/arch/arc/include/asm/Kbuild @@ -5,5 +5,6 @@ generic-y +=3D extable.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h generic-y +=3D parport.h +generic-y +=3D ring_buffer.h generic-y +=3D user.h generic-y +=3D text-patching.h diff --git a/arch/arm/include/asm/Kbuild b/arch/arm/include/asm/Kbuild index 03657ff8fbe3..decad5f2c826 100644 --- a/arch/arm/include/asm/Kbuild +++ b/arch/arm/include/asm/Kbuild @@ -3,6 +3,7 @@ generic-y +=3D early_ioremap.h generic-y +=3D extable.h generic-y +=3D flat.h generic-y +=3D parport.h +generic-y +=3D ring_buffer.h =20 generated-y +=3D mach-types.h generated-y +=3D unistd-nr.h diff --git a/arch/arm64/include/asm/ring_buffer.h b/arch/arm64/include/asm/= ring_buffer.h new file mode 100644 index 000000000000..62316c406888 --- /dev/null +++ b/arch/arm64/include/asm/ring_buffer.h @@ -0,0 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#ifndef _ASM_ARM64_RING_BUFFER_H +#define _ASM_ARM64_RING_BUFFER_H + +#include + +/* Flush D-cache on persistent ring buffer */ +#define arch_ring_buffer_flush_range(start, end) dcache_clean_pop(start, e= nd) + +#endif /* _ASM_ARM64_RING_BUFFER_H */ diff --git a/arch/csky/include/asm/Kbuild b/arch/csky/include/asm/Kbuild index 3a5c7f6e5aac..7dca0c6cdc84 100644 --- a/arch/csky/include/asm/Kbuild +++ b/arch/csky/include/asm/Kbuild @@ -9,6 +9,7 @@ generic-y +=3D qrwlock.h generic-y +=3D qrwlock_types.h generic-y +=3D qspinlock.h generic-y +=3D parport.h +generic-y +=3D ring_buffer.h generic-y +=3D user.h generic-y +=3D vmlinux.lds.h generic-y +=3D text-patching.h diff --git a/arch/hexagon/include/asm/Kbuild b/arch/hexagon/include/asm/Kbu= ild index 1efa1e993d4b..0f887d4238ed 100644 --- a/arch/hexagon/include/asm/Kbuild +++ b/arch/hexagon/include/asm/Kbuild @@ -5,4 +5,5 @@ generic-y +=3D extable.h generic-y +=3D iomap.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D text-patching.h diff --git a/arch/loongarch/include/asm/Kbuild b/arch/loongarch/include/asm= /Kbuild index 9034b583a88a..7e92957baf6a 100644 --- a/arch/loongarch/include/asm/Kbuild +++ b/arch/loongarch/include/asm/Kbuild @@ -10,5 +10,6 @@ generic-y +=3D qrwlock.h generic-y +=3D user.h generic-y +=3D ioctl.h generic-y +=3D mmzone.h +generic-y +=3D ring_buffer.h generic-y +=3D statfs.h generic-y +=3D text-patching.h diff --git a/arch/m68k/include/asm/Kbuild b/arch/m68k/include/asm/Kbuild index b282e0dd8dc1..62543bf305ff 100644 --- a/arch/m68k/include/asm/Kbuild +++ b/arch/m68k/include/asm/Kbuild @@ -3,5 +3,6 @@ generated-y +=3D syscall_table.h generic-y +=3D extable.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D spinlock.h generic-y +=3D text-patching.h diff --git a/arch/microblaze/include/asm/Kbuild b/arch/microblaze/include/a= sm/Kbuild index 7178f990e8b3..0030309b47ad 100644 --- a/arch/microblaze/include/asm/Kbuild +++ b/arch/microblaze/include/asm/Kbuild @@ -5,6 +5,7 @@ generic-y +=3D extable.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h generic-y +=3D parport.h +generic-y +=3D ring_buffer.h generic-y +=3D syscalls.h generic-y +=3D tlb.h generic-y +=3D user.h diff --git a/arch/mips/include/asm/Kbuild b/arch/mips/include/asm/Kbuild index 684569b2ecd6..9771c3d85074 100644 --- a/arch/mips/include/asm/Kbuild +++ b/arch/mips/include/asm/Kbuild @@ -12,5 +12,6 @@ generic-y +=3D mcs_spinlock.h generic-y +=3D parport.h generic-y +=3D qrwlock.h generic-y +=3D qspinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D user.h generic-y +=3D text-patching.h diff --git a/arch/nios2/include/asm/Kbuild b/arch/nios2/include/asm/Kbuild index 28004301c236..0a2530964413 100644 --- a/arch/nios2/include/asm/Kbuild +++ b/arch/nios2/include/asm/Kbuild @@ -5,6 +5,7 @@ generic-y +=3D cmpxchg.h generic-y +=3D extable.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D spinlock.h generic-y +=3D user.h generic-y +=3D text-patching.h diff --git a/arch/openrisc/include/asm/Kbuild b/arch/openrisc/include/asm/K= build index cef49d60d74c..8aa34621702d 100644 --- a/arch/openrisc/include/asm/Kbuild +++ b/arch/openrisc/include/asm/Kbuild @@ -8,4 +8,5 @@ generic-y +=3D spinlock_types.h generic-y +=3D spinlock.h generic-y +=3D qrwlock_types.h generic-y +=3D qrwlock.h +generic-y +=3D ring_buffer.h generic-y +=3D user.h diff --git a/arch/parisc/include/asm/Kbuild b/arch/parisc/include/asm/Kbuild index 4fb596d94c89..d48d158f7241 100644 --- a/arch/parisc/include/asm/Kbuild +++ b/arch/parisc/include/asm/Kbuild @@ -4,4 +4,5 @@ generated-y +=3D syscall_table_64.h generic-y +=3D agp.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D user.h diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbu= ild index 2e23533b67e3..805b5aeebb6f 100644 --- a/arch/powerpc/include/asm/Kbuild +++ b/arch/powerpc/include/asm/Kbuild @@ -5,4 +5,5 @@ generated-y +=3D syscall_table_spu.h generic-y +=3D agp.h generic-y +=3D mcs_spinlock.h generic-y +=3D qrwlock.h +generic-y +=3D ring_buffer.h generic-y +=3D early_ioremap.h diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild index bd5fc9403295..7721b63642f4 100644 --- a/arch/riscv/include/asm/Kbuild +++ b/arch/riscv/include/asm/Kbuild @@ -14,5 +14,6 @@ generic-y +=3D ticket_spinlock.h generic-y +=3D qrwlock.h generic-y +=3D qrwlock_types.h generic-y +=3D qspinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D user.h generic-y +=3D vmlinux.lds.h diff --git a/arch/s390/include/asm/Kbuild b/arch/s390/include/asm/Kbuild index 80bad7de7a04..0c1fc47c3ba0 100644 --- a/arch/s390/include/asm/Kbuild +++ b/arch/s390/include/asm/Kbuild @@ -7,3 +7,4 @@ generated-y +=3D unistd_nr.h generic-y +=3D asm-offsets.h generic-y +=3D mcs_spinlock.h generic-y +=3D mmzone.h +generic-y +=3D ring_buffer.h diff --git a/arch/sh/include/asm/Kbuild b/arch/sh/include/asm/Kbuild index 4d3f10ed8275..f0403d3ee8ab 100644 --- a/arch/sh/include/asm/Kbuild +++ b/arch/sh/include/asm/Kbuild @@ -3,4 +3,5 @@ generated-y +=3D syscall_table.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h generic-y +=3D parport.h +generic-y +=3D ring_buffer.h generic-y +=3D text-patching.h diff --git a/arch/sparc/include/asm/Kbuild b/arch/sparc/include/asm/Kbuild index 17ee8a273aa6..49c6bb326b75 100644 --- a/arch/sparc/include/asm/Kbuild +++ b/arch/sparc/include/asm/Kbuild @@ -4,4 +4,5 @@ generated-y +=3D syscall_table_64.h generic-y +=3D agp.h generic-y +=3D kvm_para.h generic-y +=3D mcs_spinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D text-patching.h diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild index 1b9b82bbe322..2a1629ba8140 100644 --- a/arch/um/include/asm/Kbuild +++ b/arch/um/include/asm/Kbuild @@ -17,6 +17,7 @@ generic-y +=3D module.lds.h generic-y +=3D parport.h generic-y +=3D percpu.h generic-y +=3D preempt.h +generic-y +=3D ring_buffer.h generic-y +=3D runtime-const.h generic-y +=3D softirq_stack.h generic-y +=3D switch_to.h diff --git a/arch/x86/include/asm/Kbuild b/arch/x86/include/asm/Kbuild index 4566000e15c4..078fd2c0d69d 100644 --- a/arch/x86/include/asm/Kbuild +++ b/arch/x86/include/asm/Kbuild @@ -14,3 +14,4 @@ generic-y +=3D early_ioremap.h generic-y +=3D fprobe.h generic-y +=3D mcs_spinlock.h generic-y +=3D mmzone.h +generic-y +=3D ring_buffer.h diff --git a/arch/xtensa/include/asm/Kbuild b/arch/xtensa/include/asm/Kbuild index 13fe45dea296..e57af619263a 100644 --- a/arch/xtensa/include/asm/Kbuild +++ b/arch/xtensa/include/asm/Kbuild @@ -6,5 +6,6 @@ generic-y +=3D mcs_spinlock.h generic-y +=3D parport.h generic-y +=3D qrwlock.h generic-y +=3D qspinlock.h +generic-y +=3D ring_buffer.h generic-y +=3D user.h generic-y +=3D text-patching.h diff --git a/include/asm-generic/ring_buffer.h b/include/asm-generic/ring_b= uffer.h new file mode 100644 index 000000000000..dbe94f5785f9 --- /dev/null +++ b/include/asm-generic/ring_buffer.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Generiuc arch dependent ring_buffer macros. + */ +#ifndef __ASM_GENERIC_RING_BUFFER_H__ +#define __ASM_GENERIC_RING_BUFFER_H__ + +#include + +/* Flush cache on ring buffer range if needed */ +#define arch_ring_buffer_flush_range(start, end) flush_cache_vmap(start, e= nd) + +#endif /* __ASM_GENERIC_RING_BUFFER_H__ */ diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 17d0ea0cc3e6..b6f3ac99834f 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -6,6 +6,7 @@ */ #include #include +#include #include #include #include @@ -30,6 +31,7 @@ #include #include =20 +#include #include #include #include @@ -589,6 +591,7 @@ struct trace_buffer { =20 unsigned long range_addr_start; unsigned long range_addr_end; + struct notifier_block flush_nb; =20 struct ring_buffer_meta *meta; =20 @@ -2471,6 +2474,16 @@ static void rb_free_cpu_buffer(struct ring_buffer_pe= r_cpu *cpu_buffer) kfree(cpu_buffer); } =20 +/* 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); + + ring_buffer_record_off(buffer); + arch_ring_buffer_flush_range(buffer->range_addr_start, buffer->range_addr= _end); + return NOTIFY_DONE; +} + static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flag= s, int order, unsigned long start, unsigned long end, @@ -2590,6 +2603,12 @@ static struct trace_buffer *alloc_buffer(unsigned lo= ng size, unsigned flags, =20 mutex_init(&buffer->mutex); =20 + /* Persistent ring buffer needs to flush cache before reboot. */ + if (start & end) { + buffer->flush_nb.notifier_call =3D rb_flush_buffer_cb; + atomic_notifier_chain_register(&panic_notifier_list, &buffer->flush_nb); + } + return_ptr(buffer); =20 fail_free_buffers: @@ -2677,6 +2696,9 @@ ring_buffer_free(struct trace_buffer *buffer) { int cpu; =20 + if (buffer->range_addr_start && buffer->range_addr_end) + atomic_notifier_chain_unregister(&panic_notifier_list, &buffer->flush_nb= ); + cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); =20 irq_work_sync(&buffer->irq_work.work); From nobody Thu Apr 9 14:56:42 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 7594A392C3E; Sat, 7 Mar 2026 14:26:42 +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=1772893602; cv=none; b=fym1LcKC+NwV+Ke1ofkKvhP5gZUanasQwOFhKy2eP3kMHoCuozKgmWlRMuy/8m+FaEe4o9PPX1cmxDTsaE54v9VbpETUAownTHlci62GIunsZ42NQCG16LJzdf34mbOpOYT47M3/hvuVPH4hBYvh+MT9jWMn/MY241JEJ8m8rZQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772893602; c=relaxed/simple; bh=102Xuq/hE8JwZtM2Ay7bKp0Yq2/d7+YhGMylDwS6JDs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=kR567JCWBMxkAFx4SxzU0jaUD5OtnWKBzFmLzBPT5SMwkAI/M9ShmiOGFs08q2MVXhUh22gKTe/FrOr1Xw26ZocxOnJ+x8Y68zm8WczalkHNBKBqhImN2TS+2QqbznkY5g3jmhddnv2Du3ZABYu3Tl5duAwyw7LXEBwU9R8JUMk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b/SaL4F+; 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="b/SaL4F+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C68FAC19422; Sat, 7 Mar 2026 14:26:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772893602; bh=102Xuq/hE8JwZtM2Ay7bKp0Yq2/d7+YhGMylDwS6JDs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b/SaL4F+EsYxZLsQfySYgZlebPgxJWIDdUuQ+FYYQsdeuQ+UaYI6MRgEVBAFZusPy ljJFeAIkT4LwwD4EjSF2pPinnVr6ve/iGyy2SEzzsXeXhFEq6Sv1be437FC+YsUpdJ TmLTzTarHQMRcF0GEKKTDvyi+9Y5i2sr1XORseNK3XA1qFFvZTxUkR3tvL0oNCbD1w 7qokLws3NSTd6vvadspWatn1YBNIKkwTGmmRyyCiplzXRma5r0xp/NMLk6zJBHs9zv CuDDKJo05KmRPIw13cWi39Y4Fa62GfR40yXT+GA5K4i8QnAxigzzNImOEcdjPlIaYM 2b+dHPOBRK2hA== From: "Masami Hiramatsu (Google)" To: Steven Rostedt Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH v7 2/2] ring-buffer: Skip invalid sub-buffers when validating persistent ring buffer Date: Sat, 7 Mar 2026 23:26:38 +0900 Message-ID: <177289359843.248514.164858607457269337.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <177289358078.248514.14947007976699929481.stgit@devnote2> References: <177289358078.248514.14947007976699929481.stgit@devnote2> 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) Skip invalid sub-buffers when validating the persistent ring buffer instead of discarding the entire ring buffer. Only skipped buffers are invalidated (cleared). If the cache data in memory fails to be synchronized during a reboot, the persistent ring buffer may become partially corrupted, but other sub-buffers may still contain readable event data. Only discard the subbuffersa that ar found to be corrupted. Signed-off-by: Masami Hiramatsu (Google) --- Changes in v7: - Combined with Handling RB_MISSED_* flags patch, focus on validation at = boot. - Remove checking subbuffer data when validating metadata, because it sho= uld be done later. - Do not mark the discarded sub buffer page but just reset it. Changes in v6: - Show invalid page detection message once per CPU. Changes in v5: - Instead of showing errors for each page, just show the number of discarded pages at last. Changes in v3: - Record missed data event on commit. --- kernel/trace/ring_buffer.c | 63 +++++++++++++++++++++++-----------------= ---- 1 file changed, 33 insertions(+), 30 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index b6f3ac99834f..8599de5cf59b 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -396,6 +396,12 @@ static __always_inline unsigned int rb_page_commit(str= uct buffer_page *bpage) return local_read(&bpage->page->commit); } =20 +/* Size is determined by what has been committed */ +static __always_inline unsigned int rb_page_size(struct buffer_page *bpage) +{ + return rb_page_commit(bpage) & ~RB_MISSED_MASK; +} + static void free_buffer_page(struct buffer_page *bpage) { /* Range pages are not to be freed */ @@ -1819,7 +1825,7 @@ static bool rb_cpu_meta_valid(struct ring_buffer_cpu_= meta *meta, int cpu, =20 bitmap_clear(subbuf_mask, 0, meta->nr_subbufs); =20 - /* Is the meta buffers and the subbufs themselves have correct data? */ + /* Is the meta buffers themselves have correct data? */ for (i =3D 0; i < meta->nr_subbufs; i++) { if (meta->buffers[i] < 0 || meta->buffers[i] >=3D meta->nr_subbufs) { @@ -1827,11 +1833,6 @@ static bool rb_cpu_meta_valid(struct ring_buffer_cpu= _meta *meta, int cpu, return false; } =20 - if ((unsigned)local_read(&subbuf->commit) > subbuf_size) { - pr_info("Ring buffer boot meta [%d] buffer invalid commit\n", cpu); - return false; - } - if (test_bit(meta->buffers[i], subbuf_mask)) { pr_info("Ring buffer boot meta [%d] array has duplicates\n", cpu); return false; @@ -1902,13 +1903,16 @@ static int rb_read_data_buffer(struct buffer_data_p= age *dpage, int tail, int cpu return events; } =20 -static int rb_validate_buffer(struct buffer_data_page *dpage, int cpu) +static int rb_validate_buffer(struct buffer_data_page *dpage, int cpu, + struct ring_buffer_cpu_meta *meta) { unsigned long long ts; u64 delta; int tail; =20 tail =3D local_read(&dpage->commit); + if (tail <=3D 0 || tail > meta->subbuf_size) + return -1; return rb_read_data_buffer(dpage, tail, cpu, &ts, &delta); } =20 @@ -1919,6 +1923,7 @@ static void rb_meta_validate_events(struct ring_buffe= r_per_cpu *cpu_buffer) struct buffer_page *head_page, *orig_head; unsigned long entry_bytes =3D 0; unsigned long entries =3D 0; + int discarded =3D 0; int ret; u64 ts; int i; @@ -1929,13 +1934,13 @@ static void rb_meta_validate_events(struct ring_buf= fer_per_cpu *cpu_buffer) orig_head =3D head_page =3D cpu_buffer->head_page; =20 /* Do the reader page first */ - ret =3D rb_validate_buffer(cpu_buffer->reader_page->page, cpu_buffer->cpu= ); + ret =3D rb_validate_buffer(cpu_buffer->reader_page->page, cpu_buffer->cpu= , meta); if (ret < 0) { pr_info("Ring buffer reader page is invalid\n"); goto invalid; } entries +=3D ret; - entry_bytes +=3D local_read(&cpu_buffer->reader_page->page->commit); + entry_bytes +=3D rb_page_size(cpu_buffer->reader_page); local_set(&cpu_buffer->reader_page->entries, ret); =20 ts =3D head_page->page->time_stamp; @@ -1964,7 +1969,7 @@ static void rb_meta_validate_events(struct ring_buffe= r_per_cpu *cpu_buffer) break; =20 /* Stop rewind if the page is invalid. */ - ret =3D rb_validate_buffer(head_page->page, cpu_buffer->cpu); + ret =3D rb_validate_buffer(head_page->page, cpu_buffer->cpu, meta); if (ret < 0) break; =20 @@ -2043,21 +2048,24 @@ static void rb_meta_validate_events(struct ring_buf= fer_per_cpu *cpu_buffer) if (head_page =3D=3D cpu_buffer->reader_page) continue; =20 - ret =3D rb_validate_buffer(head_page->page, cpu_buffer->cpu); + ret =3D rb_validate_buffer(head_page->page, cpu_buffer->cpu, meta); if (ret < 0) { - pr_info("Ring buffer meta [%d] invalid buffer page\n", - cpu_buffer->cpu); - goto invalid; - } - - /* If the buffer has content, update pages_touched */ - if (ret) - local_inc(&cpu_buffer->pages_touched); - - entries +=3D ret; - entry_bytes +=3D local_read(&head_page->page->commit); - local_set(&cpu_buffer->head_page->entries, ret); + if (!discarded) + pr_info("Ring buffer meta [%d] invalid buffer page detected\n", + cpu_buffer->cpu); + discarded++; + /* Instead of discard whole ring buffer, discard only this sub-buffer. = */ + local_set(&head_page->entries, 0); + local_set(&head_page->page->commit, RB_MISSED_EVENTS); + } else { + /* If the buffer has content, update pages_touched */ + if (ret) + local_inc(&cpu_buffer->pages_touched); =20 + entries +=3D ret; + entry_bytes +=3D rb_page_size(head_page); + local_set(&cpu_buffer->head_page->entries, ret); + } if (head_page =3D=3D cpu_buffer->commit_page) break; } @@ -2071,7 +2079,8 @@ static void rb_meta_validate_events(struct ring_buffe= r_per_cpu *cpu_buffer) local_set(&cpu_buffer->entries, entries); local_set(&cpu_buffer->entries_bytes, entry_bytes); =20 - pr_info("Ring buffer meta [%d] is from previous boot!\n", cpu_buffer->cpu= ); + pr_info("Ring buffer meta [%d] is from previous boot! (%d pages discarded= )\n", + cpu_buffer->cpu, discarded); return; =20 invalid: @@ -3258,12 +3267,6 @@ rb_iter_head_event(struct ring_buffer_iter *iter) return NULL; } =20 -/* Size is determined by what has been committed */ -static __always_inline unsigned rb_page_size(struct buffer_page *bpage) -{ - return rb_page_commit(bpage) & ~RB_MISSED_MASK; -} - static __always_inline unsigned rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) {