From nobody Mon Feb 9 16:50:57 2026 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B85E3335077 for ; Mon, 26 Jan 2026 10:44:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769424283; cv=none; b=ubtcoJqeLlxq4KK64kPWYhfNygh9wlvfxfQIVmIjdmyhPjAWWMyCn3XG4SjKUqpn8cNe53f0TlK/WpFwFrnepkwxGb63zRxRxw2nJwi3ol2NpmKTzmPHq5wmUrkMp7Y6SyP2ZqJBVbakJaKY2fGTqq++u83mm07hmhngYWdo1ZU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769424283; c=relaxed/simple; bh=gp7F5cD+kYeHWtUIfcCipQxZUN+sI3O+EG7SJsSJnPA=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=C8ZwMlqRKHECVpkZQRisqt2Y1wFuvYoUVXCy1X+jpSptsQUAdwgI1CJpgyqhaBE8ClbbA24FG6igkYgb0dlAd5cRjNsODTyTvgCvVqgxOm1irpWx7g7iBqeRHYtj73J4HtMhhfxFDF7prrz6iMRufmDFyZ8e4D14aFRIF/7A3Mk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=K9zYIJQP; arc=none smtp.client-ip=209.85.128.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="K9zYIJQP" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-47ee868f5adso45986195e9.0 for ; Mon, 26 Jan 2026 02:44:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1769424278; x=1770029078; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=JYZiWMM3wmPHmhb2wXGAbmbPsN3SxiXynR3jqzU+/ns=; b=K9zYIJQPCridnnPaSznr+u/R0Ml1ByvhcpyFFiz0LI7l7uVQ6Tq+djw8zOz5tszJrR /FzssvRQ/7LviICjHQPUFQjzIge0WflYGAx9r51lcemsNjrQFAOd3FfWspyfqmxVXJWR ogVbV+oGNTvoaunwfrAi6eUs6c/bdics5IV6ySjvfxXQMoAGYq/wqXLN5ATLl0qO/V0J tO7jpGdFRbuOJu66UWkYQ9gFbkUeu3hFEY/ZYmThtckgPqAuoCa/NBnKP2Coc/zeKklN /NQwwQGrZulVb7wmNgbMqUYXNI20pjv/SHrWzSqB45OJGOyjBKrac2jMvLLKEsa4s2vr hU+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769424278; x=1770029078; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=JYZiWMM3wmPHmhb2wXGAbmbPsN3SxiXynR3jqzU+/ns=; b=kFHja7c61LJMuhbpRcPb37GBwfXtz72/kpg7Bddtdqn4V6DSEtGDW/eLb2/PhZZcmp qKaXcTIy9KRTW9BoOYTCvaianqRO5JbH6BC58slHN+0f6gTOVqCGT1XtKvqzyfxzquIl 1Vy+DsNUqPBPxTwQfSQGDESXhcMZ1MVVvw+w9n+aJTHho4XOepDtLtVYR3Ke0oU7XUmY ZVa2zVg6s1cAxrjMIq8BniwEHZhoje8FPAX8kQ/cLJkcUn+6DhuV6I0nsxr3ZhnpTDZf N9jFd78qNgVXnIlcnw9d9j+86r4Tm2/wlU9ANfoYMp95WmloJteFUdD1Q9tlvRuZz1uS mbeg== X-Forwarded-Encrypted: i=1; AJvYcCUwb7oJMuqSazN9VKoS7jaAMVGMibocSxFTwA1W3rtw2/FRNeCURhiB3d4WgbPlzJ1V2SoM66ZCPpFtkWw=@vger.kernel.org X-Gm-Message-State: AOJu0YyGXTHu8a6AxXGxCBWAp/6y/7TP1qlQ7HZmOnZtd85tzUKIJ4Tf MJgHTy1j9Ni6Qas4Zgn2XhDpXLw2YUbJy2/jYB14jlRmM5pRONXdkZhc1F6GDcN0OrWVzlfTJjG oN6PIpIPSe+y/vwkKU/mpCw== X-Received: from wmxa6-n1.prod.google.com ([2002:a05:600d:6446:10b0:47d:5dae:74f0]) (user=vdonnefort job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:620c:b0:477:9a28:b09a with SMTP id 5b1f17b1804b1-4805ccd0f58mr69070115e9.0.1769424278162; Mon, 26 Jan 2026 02:44:38 -0800 (PST) Date: Mon, 26 Jan 2026 10:44:02 +0000 In-Reply-To: <20260126104419.1649811-1-vdonnefort@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260126104419.1649811-1-vdonnefort@google.com> X-Mailer: git-send-email 2.52.0.457.g6b5491de43-goog Message-ID: <20260126104419.1649811-14-vdonnefort@google.com> Subject: [PATCH v10 13/30] tracing: Introduce simple_ring_buffer From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, jstultz@google.com, qperret@google.com, will@kernel.org, aneesh.kumar@kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org, Vincent Donnefort Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a simple implementation of the kernel ring-buffer. This intends to be used later by ring-buffer remotes such as the pKVM hypervisor, hence the need for a cut down version (write only) without any dependency. Signed-off-by: Vincent Donnefort diff --git a/include/linux/simple_ring_buffer.h b/include/linux/simple_ring= _buffer.h new file mode 100644 index 000000000000..f324df2f875b --- /dev/null +++ b/include/linux/simple_ring_buffer.h @@ -0,0 +1,113 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_SIMPLE_RING_BUFFER_H +#define _LINUX_SIMPLE_RING_BUFFER_H + +#include +#include +#include +#include + +/* + * Ideally those struct would stay private but the caller needs to know + * the allocation size for simple_ring_buffer_init(). + */ +struct simple_buffer_page { + struct list_head link; + struct buffer_data_page *page; + u64 entries; + u32 write; + u32 id; +}; + +struct simple_rb_per_cpu { + struct simple_buffer_page *tail_page; + struct simple_buffer_page *reader_page; + struct simple_buffer_page *head_page; + struct simple_buffer_page *bpages; + struct trace_buffer_meta *meta; + u32 nr_pages; + +#define SIMPLE_RB_UNAVAILABLE 0 +#define SIMPLE_RB_READY 1 +#define SIMPLE_RB_WRITING 2 + u32 status; + + u64 last_overrun; + u64 write_stamp; + + struct simple_rb_cbs *cbs; +}; + +/** + * simple_ring_buffer_init - Init @cpu_buffer based on @desc + * + * @cpu_buffer: A simple_rb_per_cpu buffer to init, allocated by the calle= r. + * @bpages: Array of simple_buffer_pages, with as many elements as @desc->= nr_page_va + * @desc: A ring_buffer_desc + * + * Returns: 0 on success or -EINVAL if the content of @desc is invalid + */ +int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct s= imple_buffer_page *bpages, + const struct ring_buffer_desc *desc); + +/** + * simple_ring_buffer_unload - Prepare @cpu_buffer for deletion + * + * @cpu_buffer: A simple_rb_per_cpu that will be deleted. + */ +void simple_ring_buffer_unload(struct simple_rb_per_cpu *cpu_buffer); + +/** + * simple_ring_buffer_reserve - Reserve an entry in @cpu_buffer + * + * @cpu_buffer: A simple_rb_per_cpu + * @length: Size of the entry in bytes + * @timestamp: Timestamp of the entry + * + * Returns the address of the entry where to write data or NULL + */ +void *simple_ring_buffer_reserve(struct simple_rb_per_cpu *cpu_buffer, uns= igned long length, + u64 timestamp); + +/** + * simple_ring_buffer_commit - Commit the entry reserved with simple_ring_= buffer_reserve() + * + * @cpu_buffer: The simple_rb_per_cpu where the entry has been reserved + */ +void simple_ring_buffer_commit(struct simple_rb_per_cpu *cpu_buffer); + +/** + * simple_ring_buffer_enable_tracing - Enable or disable writing to @cpu_b= uffer + * + * @cpu_buffer: A simple_rb_per_cpu + * @enable: True to enable tracing, False to disable it + * + * Returns 0 on success or -ENODEV if @cpu_buffer was unloaded + */ +int simple_ring_buffer_enable_tracing(struct simple_rb_per_cpu *cpu_buffer= , bool enable); + +/** + * simple_ring_buffer_reset - Reset @cpu_buffer + * + * @cpu_buffer: A simple_rb_per_cpu + * + * This will not clear the content of the data, only reset counters and po= inters + * + * Returns 0 on success or -ENODEV if @cpu_buffer was unloaded. + */ +int simple_ring_buffer_reset(struct simple_rb_per_cpu *cpu_buffer); + +/** + * simple_ring_buffer_swap_reader_page - Swap ring-buffer head with the re= ader + * + * This function enables consuming reading. It ensures the current head pa= ge will not be overwritten + * and can be safely read. + * + * @cpu_buffer: A simple_rb_per_cpu + * + * Returns 0 on success, -ENODEV if @cpu_buffer was unloaded or -EBUSY if = we failed to catch the + * head page. + */ +int simple_ring_buffer_swap_reader_page(struct simple_rb_per_cpu *cpu_buff= er); + +#endif diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 135edf143073..dfaf1af8862e 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -1281,4 +1281,7 @@ source "kernel/trace/rv/Kconfig" config TRACE_REMOTE bool =20 +config SIMPLE_RING_BUFFER + bool + endif # FTRACE diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 6e75d710fc25..efe12e282f8c 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -128,4 +128,5 @@ obj-$(CONFIG_TRACEPOINT_BENCHMARK) +=3D trace_benchmark= .o obj-$(CONFIG_RV) +=3D rv/ =20 obj-$(CONFIG_TRACE_REMOTE) +=3D trace_remote.o +obj-$(CONFIG_SIMPLE_RING_BUFFER) +=3D simple_ring_buffer.o libftrace-y :=3D ftrace.o diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_b= uffer.c new file mode 100644 index 000000000000..1d1f40c8c6d8 --- /dev/null +++ b/kernel/trace/simple_ring_buffer.c @@ -0,0 +1,415 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2025 - Google LLC + * Author: Vincent Donnefort + */ + +#include +#include + +#include +#include + +enum simple_rb_link_type { + SIMPLE_RB_LINK_NORMAL =3D 0, + SIMPLE_RB_LINK_HEAD =3D 1, + SIMPLE_RB_LINK_HEAD_MOVING +}; + +#define SIMPLE_RB_LINK_MASK ~(SIMPLE_RB_LINK_HEAD | SIMPLE_RB_LINK_HEAD_MO= VING) + +static void simple_bpage_set_head_link(struct simple_buffer_page *bpage) +{ + unsigned long link =3D (unsigned long)bpage->link.next; + + link &=3D SIMPLE_RB_LINK_MASK; + link |=3D SIMPLE_RB_LINK_HEAD; + + /* + * Paired with simple_rb_find_head() to order access between the head + * link and overrun. It ensures we always report an up-to-date value + * after swapping the reader page. + */ + smp_store_release(&bpage->link.next, (struct list_head *)link); +} + +static bool simple_bpage_unset_head_link(struct simple_buffer_page *bpage, + struct simple_buffer_page *dst, + enum simple_rb_link_type new_type) +{ + unsigned long *link =3D (unsigned long *)(&bpage->link.next); + unsigned long old =3D (*link & SIMPLE_RB_LINK_MASK) | SIMPLE_RB_LINK_HEAD; + unsigned long new =3D (unsigned long)(&dst->link) | new_type; + + return try_cmpxchg(link, &old, new); +} + +static void simple_bpage_set_normal_link(struct simple_buffer_page *bpage) +{ + unsigned long link =3D (unsigned long)bpage->link.next; + + WRITE_ONCE(bpage->link.next, (struct list_head *)(link & SIMPLE_RB_LINK_M= ASK)); +} + +static struct simple_buffer_page *simple_bpage_from_link(struct list_head = *link) +{ + unsigned long ptr =3D (unsigned long)link & SIMPLE_RB_LINK_MASK; + + return container_of((struct list_head *)ptr, struct simple_buffer_page, l= ink); +} + +static struct simple_buffer_page *simple_bpage_next_page(struct simple_buf= fer_page *bpage) +{ + return simple_bpage_from_link(bpage->link.next); +} + +static void simple_bpage_reset(struct simple_buffer_page *bpage) +{ + bpage->write =3D 0; + bpage->entries =3D 0; + + local_set(&bpage->page->commit, 0); +} + +static void simple_bpage_init(struct simple_buffer_page *bpage, unsigned l= ong page) +{ + INIT_LIST_HEAD(&bpage->link); + bpage->page =3D (struct buffer_data_page *)page; + + simple_bpage_reset(bpage); +} + +#define simple_rb_meta_inc(__meta, __inc) \ + WRITE_ONCE((__meta), (__meta + __inc)) + +static bool simple_rb_loaded(struct simple_rb_per_cpu *cpu_buffer) +{ + return !!cpu_buffer->bpages; +} + +static int simple_rb_find_head(struct simple_rb_per_cpu *cpu_buffer) +{ + int retry =3D cpu_buffer->nr_pages * 2; + struct simple_buffer_page *head; + + head =3D cpu_buffer->head_page; + + while (retry--) { + unsigned long link; + +spin: + /* See smp_store_release in simple_bpage_set_head_link() */ + link =3D (unsigned long)smp_load_acquire(&head->link.prev->next); + + switch (link & ~SIMPLE_RB_LINK_MASK) { + /* Found the head */ + case SIMPLE_RB_LINK_HEAD: + cpu_buffer->head_page =3D head; + return 0; + /* The writer caught the head, we can spin, that won't be long */ + case SIMPLE_RB_LINK_HEAD_MOVING: + goto spin; + } + + head =3D simple_bpage_next_page(head); + } + + return -EBUSY; +} + +int simple_ring_buffer_swap_reader_page(struct simple_rb_per_cpu *cpu_buff= er) +{ + struct simple_buffer_page *last, *head, *reader; + unsigned long overrun; + int retry =3D 8; + int ret; + + if (!simple_rb_loaded(cpu_buffer)) + return -ENODEV; + + reader =3D cpu_buffer->reader_page; + + do { + /* Run after the writer to find the head */ + ret =3D simple_rb_find_head(cpu_buffer); + if (ret) + return ret; + + head =3D cpu_buffer->head_page; + + /* Connect the reader page around the header page */ + reader->link.next =3D head->link.next; + reader->link.prev =3D head->link.prev; + + /* The last page before the head */ + last =3D simple_bpage_from_link(head->link.prev); + + /* The reader page points to the new header page */ + simple_bpage_set_head_link(reader); + + overrun =3D cpu_buffer->meta->overrun; + } while (!simple_bpage_unset_head_link(last, reader, SIMPLE_RB_LINK_NORMA= L) && retry--); + + if (!retry) + return -EINVAL; + + cpu_buffer->head_page =3D simple_bpage_from_link(reader->link.next); + cpu_buffer->head_page->link.prev =3D &reader->link; + cpu_buffer->reader_page =3D head; + cpu_buffer->meta->reader.lost_events =3D overrun - cpu_buffer->last_overr= un; + cpu_buffer->meta->reader.id =3D cpu_buffer->reader_page->id; + cpu_buffer->last_overrun =3D overrun; + + return 0; +} +EXPORT_SYMBOL_GPL(simple_ring_buffer_swap_reader_page); + +static struct simple_buffer_page *simple_rb_move_tail(struct simple_rb_per= _cpu *cpu_buffer) +{ + struct simple_buffer_page *tail, *new_tail; + + tail =3D cpu_buffer->tail_page; + new_tail =3D simple_bpage_next_page(tail); + + if (simple_bpage_unset_head_link(tail, new_tail, SIMPLE_RB_LINK_HEAD_MOVI= NG)) { + /* + * Oh no! we've caught the head. There is none anymore and + * swap_reader will spin until we set the new one. Overrun must + * be written first, to make sure we report the correct number + * of lost events. + */ + simple_rb_meta_inc(cpu_buffer->meta->overrun, new_tail->entries); + simple_rb_meta_inc(cpu_buffer->meta->pages_lost, 1); + + simple_bpage_set_head_link(new_tail); + simple_bpage_set_normal_link(tail); + } + + simple_bpage_reset(new_tail); + cpu_buffer->tail_page =3D new_tail; + + simple_rb_meta_inc(cpu_buffer->meta->pages_touched, 1); + + return new_tail; +} + +static unsigned long rb_event_size(unsigned long length) +{ + struct ring_buffer_event *event; + + return length + RB_EVNT_HDR_SIZE + sizeof(event->array[0]); +} + +static struct ring_buffer_event * +rb_event_add_ts_extend(struct ring_buffer_event *event, u64 delta) +{ + event->type_len =3D RINGBUF_TYPE_TIME_EXTEND; + event->time_delta =3D delta & TS_MASK; + event->array[0] =3D delta >> TS_SHIFT; + + return (struct ring_buffer_event *)((unsigned long)event + 8); +} + +static struct ring_buffer_event * +simple_rb_reserve_next(struct simple_rb_per_cpu *cpu_buffer, unsigned long= length, u64 timestamp) +{ + unsigned long ts_ext_size =3D 0, event_size =3D rb_event_size(length); + struct simple_buffer_page *tail =3D cpu_buffer->tail_page; + struct ring_buffer_event *event; + u32 write, prev_write; + u64 time_delta; + + time_delta =3D timestamp - cpu_buffer->write_stamp; + + if (test_time_stamp(time_delta)) + ts_ext_size =3D 8; + + prev_write =3D tail->write; + write =3D prev_write + event_size + ts_ext_size; + + if (unlikely(write > (PAGE_SIZE - BUF_PAGE_HDR_SIZE))) + tail =3D simple_rb_move_tail(cpu_buffer); + + if (!tail->entries) { + tail->page->time_stamp =3D timestamp; + time_delta =3D 0; + ts_ext_size =3D 0; + write =3D event_size; + prev_write =3D 0; + } + + tail->write =3D write; + tail->entries++; + + cpu_buffer->write_stamp =3D timestamp; + + event =3D (struct ring_buffer_event *)(tail->page->data + prev_write); + if (ts_ext_size) { + event =3D rb_event_add_ts_extend(event, time_delta); + time_delta =3D 0; + } + + event->type_len =3D 0; + event->time_delta =3D time_delta; + event->array[0] =3D event_size - RB_EVNT_HDR_SIZE; + + return event; +} + +void *simple_ring_buffer_reserve(struct simple_rb_per_cpu *cpu_buffer, uns= igned long length, + u64 timestamp) +{ + struct ring_buffer_event *rb_event; + + if (cmpxchg(&cpu_buffer->status, SIMPLE_RB_READY, SIMPLE_RB_WRITING) !=3D= SIMPLE_RB_READY) + return NULL; + + rb_event =3D simple_rb_reserve_next(cpu_buffer, length, timestamp); + + return &rb_event->array[1]; +} +EXPORT_SYMBOL_GPL(simple_ring_buffer_reserve); + +void simple_ring_buffer_commit(struct simple_rb_per_cpu *cpu_buffer) +{ + local_set(&cpu_buffer->tail_page->page->commit, + cpu_buffer->tail_page->write); + simple_rb_meta_inc(cpu_buffer->meta->entries, 1); + + /* + * Paired with simple_rb_enable_tracing() to ensure data is + * written to the ring-buffer before teardown. + */ + smp_store_release(&cpu_buffer->status, SIMPLE_RB_READY); +} +EXPORT_SYMBOL_GPL(simple_ring_buffer_commit); + +static u32 simple_rb_enable_tracing(struct simple_rb_per_cpu *cpu_buffer, = bool enable) +{ + u32 prev_status; + + if (enable) + return cmpxchg(&cpu_buffer->status, SIMPLE_RB_UNAVAILABLE, SIMPLE_RB_REA= DY); + + /* Wait for the buffer to be released */ + do { + prev_status =3D cmpxchg_acquire(&cpu_buffer->status, + SIMPLE_RB_READY, + SIMPLE_RB_UNAVAILABLE); + } while (prev_status =3D=3D SIMPLE_RB_WRITING); + + return prev_status; +} + +int simple_ring_buffer_reset(struct simple_rb_per_cpu *cpu_buffer) +{ + struct simple_buffer_page *bpage; + u32 prev_status; + int ret; + + if (!simple_rb_loaded(cpu_buffer)) + return -ENODEV; + + prev_status =3D simple_rb_enable_tracing(cpu_buffer, false); + + ret =3D simple_rb_find_head(cpu_buffer); + if (ret) + return ret; + + bpage =3D cpu_buffer->tail_page =3D cpu_buffer->head_page; + do { + simple_bpage_reset(bpage); + bpage =3D simple_bpage_next_page(bpage); + } while (bpage !=3D cpu_buffer->head_page); + + simple_bpage_reset(cpu_buffer->reader_page); + + cpu_buffer->last_overrun =3D 0; + cpu_buffer->write_stamp =3D 0; + + cpu_buffer->meta->reader.read =3D 0; + cpu_buffer->meta->reader.lost_events =3D 0; + cpu_buffer->meta->entries =3D 0; + cpu_buffer->meta->overrun =3D 0; + cpu_buffer->meta->read =3D 0; + cpu_buffer->meta->pages_lost =3D 0; + cpu_buffer->meta->pages_touched =3D 0; + + if (prev_status =3D=3D SIMPLE_RB_READY) + simple_rb_enable_tracing(cpu_buffer, true); + + return 0; +} +EXPORT_SYMBOL_GPL(simple_ring_buffer_reset); + +int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct s= imple_buffer_page *bpages, + const struct ring_buffer_desc *desc) +{ + struct simple_buffer_page *bpage =3D bpages; + int i; + + /* At least 1 reader page and two pages in the ring-buffer */ + if (desc->nr_page_va < 3) + return -EINVAL; + + memset(cpu_buffer, 0, sizeof(*cpu_buffer)); + + cpu_buffer->bpages =3D bpages; + + cpu_buffer->meta =3D (void *)desc->meta_va; + memset(cpu_buffer->meta, 0, sizeof(*cpu_buffer->meta)); + cpu_buffer->meta->meta_page_size =3D PAGE_SIZE; + cpu_buffer->meta->nr_subbufs =3D cpu_buffer->nr_pages; + + /* The reader page is not part of the ring initially */ + simple_bpage_init(bpage, desc->page_va[0]); + bpage->id =3D 0; + + cpu_buffer->nr_pages =3D 1; + + cpu_buffer->reader_page =3D bpage; + cpu_buffer->tail_page =3D bpage + 1; + cpu_buffer->head_page =3D bpage + 1; + + for (i =3D 1; i < desc->nr_page_va; i++) { + simple_bpage_init(++bpage, desc->page_va[i]); + + bpage->link.next =3D &(bpage + 1)->link; + bpage->link.prev =3D &(bpage - 1)->link; + bpage->id =3D i; + + cpu_buffer->nr_pages =3D i + 1; + } + + /* Close the ring */ + bpage->link.next =3D &cpu_buffer->tail_page->link; + cpu_buffer->tail_page->link.prev =3D &bpage->link; + + /* The last init'ed page points to the head page */ + simple_bpage_set_head_link(bpage); + + return 0; +} +EXPORT_SYMBOL_GPL(simple_ring_buffer_init); + +void simple_ring_buffer_unload(struct simple_rb_per_cpu *cpu_buffer) +{ + if (!simple_rb_loaded(cpu_buffer)) + return; + + simple_rb_enable_tracing(cpu_buffer, false); + + cpu_buffer->bpages =3D NULL; +} +EXPORT_SYMBOL_GPL(simple_ring_buffer_unload); + +int simple_ring_buffer_enable_tracing(struct simple_rb_per_cpu *cpu_buffer= , bool enable) +{ + if (!simple_rb_loaded(cpu_buffer)) + return -ENODEV; + + simple_rb_enable_tracing(cpu_buffer, enable); + + return 0; +} +EXPORT_SYMBOL_GPL(simple_ring_buffer_enable_tracing); --=20 2.52.0.457.g6b5491de43-goog