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[209.132.180.67]) by mx.google.com with ESMTP id x3si44098250plv.26.2019.08.07.15.28.55; Wed, 07 Aug 2019 15:29:10 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389574AbfHGW1o (ORCPT + 99 others); Wed, 7 Aug 2019 18:27:44 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:51847 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388848AbfHGW1n (ORCPT ); Wed, 7 Aug 2019 18:27:43 -0400 Received: from [5.158.153.52] (helo=g2noscherz.tec.linutronix.de.) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1hvUOx-0007mg-JO; Thu, 08 Aug 2019 00:27:24 +0200 From: John Ogness To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Andrea Parri , Thomas Gleixner , Sergey Senozhatsky , Brendan Higgins Subject: [RFC PATCH v4 8/9] printk-rb: new functionality to support printk Date: Thu, 8 Aug 2019 00:32:33 +0206 Message-Id: <20190807222634.1723-9-john.ogness@linutronix.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190807222634.1723-1-john.ogness@linutronix.de> References: <20190807222634.1723-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add the following functions needed to support printk features. dataring: dataring_unused() - return free bytes ringbuffer: prb_init() - dynamically initialize a ringbuffer prb_iter_seek() - seek to an entry in the committed list prb_iter_wait_next_valid_entry() - blocking reader function prb_iter_copy() - duplicate an iterator prb_iter_entry() - get the entry of an iterator prb_unused() - wrapper for dataring_unused() prb_wait_queue() - get the ringbuffer wait queue DECLARE_PRINTKRB_SEQENTRY() - declare entry for only seq reading Also modify prb_iter_peek_next_entry() to optionally return the sequence number previous to the next entry. Signed-off-by: John Ogness --- kernel/printk/dataring.c | 29 ++++ kernel/printk/dataring.h | 3 +- kernel/printk/ringbuffer.c | 292 +++++++++++++++++++++++++++++++++++-- kernel/printk/ringbuffer.h | 46 +++++- 4 files changed, 354 insertions(+), 16 deletions(-) diff --git a/kernel/printk/dataring.c b/kernel/printk/dataring.c index 712842f2dc04..e48069dc27bc 100644 --- a/kernel/printk/dataring.c +++ b/kernel/printk/dataring.c @@ -489,6 +489,35 @@ static bool get_new_lpos(struct dataring *dr, unsigned long size, } } +/** + * dataring_unused() - Determine the unused bytes available for pushing. + * + * @dr: The data ringbuffer to check. + * + * Determine the largest possible push size that can be performed without + * invalidating existing data. + * + * Return: The number of unused bytes available for pushing. + */ +unsigned long dataring_unused(struct dataring *dr) +{ + unsigned long head_lpos; + unsigned long tail_lpos; + unsigned long size = 0; + unsigned long diff; + + to_db_size(&size); + + tail_lpos = atomic_long_read(&dr->tail_lpos); + head_lpos = atomic_long_read(&dr->head_lpos); + + diff = DATA_SIZE(dr) + tail_lpos - head_lpos; + if (diff <= size) + return 0; + + return (diff - size); +} + /** * dataring_desc_init() - Initialize a descriptor to be permanently invalid. * diff --git a/kernel/printk/dataring.h b/kernel/printk/dataring.h index c566ce228abe..896a7f855d9f 100644 --- a/kernel/printk/dataring.h +++ b/kernel/printk/dataring.h @@ -91,13 +91,14 @@ struct dataring { }; bool dataring_checksize(struct dataring *dr, unsigned long size); +unsigned long dataring_unused(struct dataring *dr); bool dataring_pop(struct dataring *dr); char *dataring_push(struct dataring *dr, unsigned long size, struct dr_desc *desc, unsigned long id); - void dataring_datablock_setid(struct dataring *dr, struct dr_desc *desc, unsigned long id); + struct dr_datablock *dataring_getdatablock(struct dataring *dr, struct dr_desc *desc, int *size); bool dataring_datablock_isvalid(struct dataring *dr, struct dr_desc *desc); diff --git a/kernel/printk/ringbuffer.c b/kernel/printk/ringbuffer.c index 053622151447..e727d9d72f65 100644 --- a/kernel/printk/ringbuffer.c +++ b/kernel/printk/ringbuffer.c @@ -3,6 +3,7 @@ #include #include #include +#include #include #include "ringbuffer.h" @@ -530,6 +531,24 @@ void prb_commit(struct prb_reserved_entry *e) } EXPORT_SYMBOL(prb_commit); +/** + * prb_unused() - Determine the unused bytes available for reserving. + * + * @rb: The ringbuffer to check. + * + * This is the public function available to writer to determine the largest + * possible reserve size that can be performed without invalidating old + * entries. + * + * Context: Any context. + * Return: The number of unused bytes available for reserving. + */ +unsigned long prb_unused(struct printk_ringbuffer *rb) +{ + return dataring_unused(&rb->dr); +} +EXPORT_SYMBOL(prb_unused); + /** * prb_iter_init() - Initialize an iterator. * @@ -543,7 +562,7 @@ EXPORT_SYMBOL(prb_commit); * * As an alternative, DECLARE_PRINTKRB_ITER() can be used. * - * The interator is initialized to the beginning of the committed list (the + * The iterator is initialized to the beginning of the committed list (the * oldest committed entry). * * Context: Any context. @@ -575,10 +594,10 @@ static void reset_iter(struct prb_iterator *iter) iter->last_seq = last_seq - 1; /* - * @last_id is only significant in EOL situations, when it is equal to - * @next_id and the iterator wants to read the entry after @last_id as - * the next entry. Set @last_id to something other than @next_id. So - * that the iterator will read @next_id as the next entry. + * @last_id is only significant in EOL situations, when it is equal + * to @next_id, in which case it reads the entry after @last_id. Set + * @last_id to something other than @next_id so that the iterator + * will read @next_id as the next entry. */ iter->last_id = iter->next_id - 1; } @@ -696,8 +715,12 @@ int prb_iter_next_valid_entry(struct prb_iterator *iter) e->seq = seq; db = dataring_getdatablock(dr, &desc, &size); - memcpy(&e->buffer[0], &db->data[0], - size > e->buffer_size ? e->buffer_size : size); + + if (e->buffer && e->buffer_size) { + memcpy(&e->buffer[0], &db->data[0], + size > e->buffer_size ? + e->buffer_size : size); + } /* * mD: @@ -726,6 +749,39 @@ int prb_iter_next_valid_entry(struct prb_iterator *iter) } EXPORT_SYMBOL(prb_iter_next_valid_entry); + +/** + * prb_iter_wait_next_valid_entry() - Blocking traverse and read. + * + * @iter: The iterator used for list traversal. + * + * This is the public function available to readers to traverse the committed + * entry list. It is the same as prb_iter_next_valid_entry() except that it + * blocks (interruptible) if the end of the commit list is reached. See + * prb_iter_next_valid_entry() for traversal/read/size details. + * + * Context: Process context. Sleeps if the end of the commit list reached. + * Return: The size of the entry data or -ERESTARTSYS if interrupted. + */ +int prb_iter_wait_next_valid_entry(struct prb_iterator *iter) +{ + int ret; + + for (;;) { + ret = wait_event_interruptible(*(iter->rb->wq), + prb_iter_peek_next_entry(iter, NULL)); + if (ret < 0) + break; + + ret = prb_iter_next_valid_entry(iter); + if (ret > 0) + break; + } + + return ret; +} +EXPORT_SYMBOL(prb_iter_wait_next_valid_entry); + /** * prb_iter_sync() - Position an iterator to that of another iterator. * @@ -764,10 +820,41 @@ void prb_iter_sync(struct prb_iterator *dst, struct prb_iterator *src) } EXPORT_SYMBOL(prb_iter_sync); +/** + * prb_iter_copy() - Copy all iterator information to another iterator. + * + * @dst: The iterator to modify. + * + * @src: The iterator to copy from. + * + * This is the public function available to readers to copy all iterator + * information of another iterator. After calling this function, @dst will + * be using the same entry and traverse the same ringbuffer, from the + * same committed entry as @src. + * + * It is not necessary for @dst to be previously initialized. + * + * Context: Any context. + * + * It is safe to call this function from any context and state. But note + * that this function is not atomic. Callers must not sync iterators that + * can be accessed by other tasks/contexts unless proper synchronization is + * used. + */ +void prb_iter_copy(struct prb_iterator *dst, struct prb_iterator *src) +{ + dst->e = src->e; + prb_iter_sync(dst, src); +} +EXPORT_SYMBOL(prb_iter_copy); + /** * prb_iter_peek_next_entry() - Check if there is a next (newer) entry. * - * @iter: The iterator used for list traversal. + * @iter: The iterator used for list traversal. + * + * @last_seq: A pointer to a variable to store the last seen sequence number. + * This may be NULL if the caller is not interested in this value. * * This is the public function available to readers to check if a newer * entry is available. @@ -775,14 +862,23 @@ EXPORT_SYMBOL(prb_iter_sync); * Context: Any context. * Return: true if there is a next entry, otherwise false. */ -bool prb_iter_peek_next_entry(struct prb_iterator *iter) +bool prb_iter_peek_next_entry(struct prb_iterator *iter, u64 *last_seq) { - DECLARE_PRINTKRB_ENTRY(e, 1); + DECLARE_PRINTKRB_SEQENTRY(e); DECLARE_PRINTKRB_ITER(iter_copy, iter->rb, &e); prb_iter_sync(&iter_copy, iter); - return (prb_iter_next_valid_entry(&iter_copy) != 0); + if (prb_iter_next_valid_entry(&iter_copy) == 0) { + if (last_seq) + *last_seq = iter_copy.last_seq; + return false; + } + + /* Pretend to have seen the previous entry. */ + if (last_seq) + *last_seq = iter_copy.last_seq - 1; + return true; } EXPORT_SYMBOL(prb_iter_peek_next_entry); @@ -807,3 +903,177 @@ unsigned long prb_getfail(struct printk_ringbuffer *rb) return atomic_long_read(&rb->fail); } EXPORT_SYMBOL(prb_getfail); + +/** + * prb_iter_seek() - Reposition an iterator based on the sequence number. + * + * @iter: The iterator used for list traversal. + * + * @last_seq: The sequence number that the iterator will have seen last. + * Use 0 to position for reading the oldest commit list entry and + * -1 to position beyond the newest commit list entry. + * + * This is the public function available to readers to reposition an iterator + * based on the commit list entry sequence number. + * + * If @last_seq exists, the iterator is positioned such that a following read + * will read the entry with the next higher sequence number. + * + * If @last_seq does not exist but a higher (newer) sequence number exists, + * the iterator is positioned such that a following read will read that + * higher entry. + * + * If @last_seq does not exist and no higher (newer) sequence number exists, + * the iterator is positioned at the end of the commit list such that a + * following read will read the next (not yet existent) entry. + * + * Context: Any context. + * Return: The last seen sequence number. + * + * From the return value (and the value of @last_seq) the caller can identify + * which of the above described scenarios occurred. + */ +u64 prb_iter_seek(struct prb_iterator *iter, u64 last_seq) +{ + DECLARE_PRINTKRB_SEQENTRY(e); + DECLARE_PRINTKRB_ITER(i, iter->rb, &e); + int l; + + /* Seek to the beginning? */ + if (last_seq == 0) { + reset_iter(iter); + goto out; + } + + /* Iterator already where it should be? */ + if (iter->last_seq == last_seq) + goto out; + + /* + * Backward seeking is not possible. Reset the iterator to the + * beginning and seek forwards. + */ + if (last_seq < iter->last_seq) + reset_iter(iter); + + /* + * Seek using a local copy and only sync with the iterator when it + * is known that the seek has not gone too far, for example when + * the desired last_seq was an invalid entry or does not exist. + */ + prb_iter_sync(&i, iter); + + prb_for_each_entry_continue(&i, l) { + if (e.seq > last_seq) + break; + + prb_iter_sync(iter, &i); + if (e.seq == last_seq) + break; + } +out: + return iter->last_seq; +} +EXPORT_SYMBOL(prb_iter_seek); + +/** + * prb_init() - Initialize a ringbuffer. + * + * @rb: The ringbuffer to initialize. + * + * @data: A pointer to a byte array for raw entry storage. + * + * @data_size_bits: The power-of-2 size fo @data. + * + * @descs: A pointer to a prb_desc array for descriptor storage. + * + * @desc_count_bits: The power-of-2 count of descriptors in @descs. + * + * @waitq: A wait queue to use for blocking readers. + * + * This is the public function available to initialize a ringbuffer. It + * allows the caller to provide the internal buffers, thus allowing the + * buffers to be allocated dynamically. + * + * As per numlist requirement of always having at least one node in the list, + * the ringbuffer structures are initialized such that: + * + * * the numlist head and tail point to descriptor 0 + * * descriptor 0 has an invalid data block and is the terminating node + * * descriptor 1 will be the next descriptor + * + * As an alternative, DECLARE_PRINTKRB() can be used. + * + * Context: Any context. + */ +void prb_init(struct printk_ringbuffer *rb, char *data, int data_size_bits, + struct prb_desc *descs, int desc_count_bits, + struct wait_queue_head *waitq) +{ + struct dataring *dr = &rb->dr; + struct numlist *nl = &rb->nl; + + rb->desc_count_bits = desc_count_bits; + rb->descs = descs; + atomic_long_set(&descs[0].id, 0); + descs[0].desc.begin_lpos = 1; + descs[0].desc.next_lpos = 1; + atomic_set(&rb->desc_next_unused, 1); + + atomic_long_set(&nl->head_id, 0); + atomic_long_set(&nl->tail_id, 0); + nl->node = prb_desc_node; + nl->node_arg = rb; + nl->busy = prb_desc_busy; + nl->busy_arg = rb; + + dr->size_bits = data_size_bits; + dr->data = data; + atomic_long_set(&dr->head_lpos, -111 * sizeof(long)); + atomic_long_set(&dr->tail_lpos, -111 * sizeof(long)); + dr->getdesc = prb_getdesc; + dr->getdesc_arg = rb; + + atomic_long_set(&rb->fail, 0); + + rb->wq = waitq; +} +EXPORT_SYMBOL(prb_init); + +/** + * prb_wait_queue() - Get the wait queue of blocking readers. + * + * @rb: The ringbuffer containing the wait queue. + * + * This is the public function available to readers to get the wait queue + * associated with a ringbuffer. All waiters on this wait queue are woken + * each time a new entry is committed. This allows a reader to implement + * their own blocking read/poll function. + * + * Context: Any context. + * Return: The ringbuffer wait queue. + */ +struct wait_queue_head *prb_wait_queue(struct printk_ringbuffer *rb) +{ + return rb->wq; +} +EXPORT_SYMBOL(prb_wait_queue); + +/** + * prb_iter_entry() - Get the prb_entry associated with an iterator. + * + * @iter: The iterator to get the entry from. + * + * This is the public function to allow readers to get the prb_entry + * structure associated with an iterator. Readers need an iterator's + * prb_entry in order to process the read data. This function is useful in + * case a caller only has an iterator, but not the associated prb_entry. + * + * Context: Any context. + * Return: The prb_entry used by @iter. + */ +struct prb_entry *prb_iter_entry(struct prb_iterator *iter) +{ + return iter->e; +} +EXPORT_SYMBOL(prb_iter_entry); diff --git a/kernel/printk/ringbuffer.h b/kernel/printk/ringbuffer.h index ec7bb21abac2..70cb9ad284d4 100644 --- a/kernel/printk/ringbuffer.h +++ b/kernel/printk/ringbuffer.h @@ -4,6 +4,7 @@ #define _LINUX_PRINTK_RINGBUFFER_H #include +#include #include "numlist.h" #include "dataring.h" @@ -48,6 +49,8 @@ struct prb_desc { * descriptor. Failure due to not being able to reserve * space in the dataring is not counted because readers * will notice a lost sequence number in that case. + * + * @wq: The wait queue used by blocking readers. */ struct printk_ringbuffer { /* private */ @@ -60,6 +63,8 @@ struct printk_ringbuffer { struct dataring dr; atomic_long_t fail; + + struct wait_queue_head *wq; }; /** @@ -138,13 +143,22 @@ void prb_commit(struct prb_reserved_entry *e); void prb_iter_init(struct prb_iterator *iter, struct printk_ringbuffer *rb, struct prb_entry *e); int prb_iter_next_valid_entry(struct prb_iterator *iter); -void prb_iter_sync(struct prb_iterator *dest, struct prb_iterator *src); -bool prb_iter_peek_next_entry(struct prb_iterator *iter); +int prb_iter_wait_next_valid_entry(struct prb_iterator *iter); +void prb_iter_sync(struct prb_iterator *dst, struct prb_iterator *src); +void prb_iter_copy(struct prb_iterator *dst, struct prb_iterator *src); +bool prb_iter_peek_next_entry(struct prb_iterator *iter, u64 *last_seq); +u64 prb_iter_seek(struct prb_iterator *iter, u64 last_seq); +struct wait_queue_head *prb_wait_queue(struct printk_ringbuffer *rb); +struct prb_entry *prb_iter_entry(struct prb_iterator *iter); /* utility functions */ unsigned long prb_getfail(struct printk_ringbuffer *rb); +void prb_init(struct printk_ringbuffer *rb, char *data, int data_size_bits, + struct prb_desc *descs, int desc_count_bits, + struct wait_queue_head *waitq); +unsigned long prb_unused(struct printk_ringbuffer *rb); -/* prototypes for callbacks used by numlist and dataring, respectively */ +/* callbacks used by numlist and dataring, respectively */ struct nl_node *prb_desc_node(unsigned long id, void *arg); bool prb_desc_busy(unsigned long id, void *arg); struct dr_desc *prb_getdesc(unsigned long id, void *arg); @@ -164,6 +178,8 @@ struct dr_desc *prb_getdesc(unsigned long id, void *arg); * * @descbits: The power-of-2 maximum amount of descriptors allowed. * + * @waitq: A wait queue to use for blocking readers. + * * The size of the data array will be the average data size multiplied by the * maximum amount of descriptors. * @@ -173,8 +189,12 @@ struct dr_desc *prb_getdesc(unsigned long id, void *arg); * * the numlist head and tail point to descriptor 0 * * descriptor 0 has an invalid data block and is the terminating node * * descriptor 1 will be the next descriptor + * + * This macro is particularly useful for static ringbuffers that should be + * immediately available and initialized. It is an alternative to + * manually initializing a ringbuffer with prb_init(). */ -#define DECLARE_PRINTKRB(name, avgdatabits, descbits) \ +#define DECLARE_PRINTKRB(name, avgdatabits, descbits, waitq) \ char _##name##_data[1 << ((avgdatabits) + (descbits))] \ __aligned(__alignof__(long)); \ struct prb_desc _##name##_descs[1 << (descbits)] = { \ @@ -206,6 +226,7 @@ struct printk_ringbuffer name = { \ .getdesc_arg = &name, \ }, \ .fail = ATOMIC_LONG_INIT(0), \ + .wq = waitq, \ } /** @@ -231,6 +252,23 @@ struct prb_entry name = { \ .buffer_size = size, \ } +/** + * DECLARE_PRINTKRB_SEQENTRY() - Declare an entry structure for sequences. + * + * @name: The name for the entry structure variable. + * + * This macro is declares and initializes an entry structure without any + * buffer. This is useful if an iterator is only interested in sequence + * numbers and so does not need to read the entry data. Also, because of + * its small size, it is safe to put on the stack. + */ +#define DECLARE_PRINTKRB_SEQENTRY(name) \ +struct prb_entry name = { \ + .seq = 0, \ + .buffer = NULL, \ + .buffer_size = 0, \ +} + /** * DECLARE_PRINTKRB_ITER() - Declare an iterator for readers. * -- 2.20.1