From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27914C433E1 for ; Tue, 19 May 2020 21:47:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED46D206C3 for ; Tue, 19 May 2020 21:47:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728392AbgESVr3 (ORCPT ); Tue, 19 May 2020 17:47:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728351AbgESVrS (ORCPT ); Tue, 19 May 2020 17:47:18 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4FF1AC08C5C1; Tue, 19 May 2020 14:47:17 -0700 (PDT) Received: from [5.158.153.53] (helo=debian-buster-darwi.lab.linutronix.de.) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1jbA4S-0002iy-5O; Tue, 19 May 2020 23:46:44 +0200 From: "Ahmed S. Darwish" To: Peter Zijlstra , Ingo Molnar , Will Deacon Cc: Thomas Gleixner , "Paul E. McKenney" , "Sebastian A. Siewior" , Steven Rostedt , LKML , "Ahmed S. Darwish" , Jonathan Corbet , linux-doc@vger.kernel.org Subject: [PATCH v1 11/25] seqlock: Add missing kernel-doc annotations Date: Tue, 19 May 2020 23:45:33 +0200 Message-Id: <20200519214547.352050-12-a.darwish@linutronix.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200519214547.352050-1-a.darwish@linutronix.de> References: <20200519214547.352050-1-a.darwish@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org A small number of the the exported seqlock.h functions are kernel-doc annotated. Since seqlock.h is now included by the kernel's RST documentation, add kernel-doc annotations for all of the remaining functions. Signed-off-by: Ahmed S. Darwish --- include/linux/seqlock.h | 414 +++++++++++++++++++++++++++++++++++----- 1 file changed, 361 insertions(+), 53 deletions(-) diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index dfec0c9c19c4..dd55555ff607 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -57,6 +57,10 @@ static inline void __seqcount_init(seqcount_t *s, const char *name, # define SEQCOUNT_DEP_MAP_INIT(lockname) \ .dep_map = { .name = #lockname } \ +/** + * seqcount_init() - runtime initializer for seqcount_t + * @s: Pointer to the &typedef seqcount_t instance + */ # define seqcount_init(s) \ do { \ static struct lock_class_key __key; \ @@ -80,13 +84,17 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s) # define seqcount_lockdep_reader_access(x) #endif -#define SEQCNT_ZERO(lockname) { .sequence = 0, SEQCOUNT_DEP_MAP_INIT(lockname)} +/** + * SEQCNT_ZERO() - static initializer for seqcount_t + * @name: Name of the &typedef seqcount_t instance + */ +#define SEQCNT_ZERO(name) { .sequence = 0, SEQCOUNT_DEP_MAP_INIT(name) } /** - * __read_seqcount_begin - begin a seq-read critical section (without barrier) - * @s: pointer to seqcount_t - * Returns: count to be passed to read_seqcount_retry + * __read_seqcount_begin() - begin a seq-read critical section (without barrier) + * @s: Pointer to &typedef seqcount_t + * Returns: count to be passed to read_seqcount_retry() * * __read_seqcount_begin is like read_seqcount_begin, but has no smp_rmb() * barrier. Callers should ensure that smp_rmb() or equivalent ordering is @@ -110,9 +118,9 @@ static inline unsigned __read_seqcount_begin(const seqcount_t *s) } /** - * raw_read_seqcount - Read the raw seqcount - * @s: pointer to seqcount_t - * Returns: count to be passed to read_seqcount_retry + * raw_read_seqcount() - Read the raw seqcount + * @s: Pointer to &typedef seqcount_t + * Returns: count to be passed to read_seqcount_retry() * * raw_read_seqcount opens a read critical section of the given * seqcount without any lockdep checking and without checking or @@ -126,13 +134,13 @@ static inline unsigned raw_read_seqcount(const seqcount_t *s) } /** - * raw_read_seqcount_begin - start seq-read critical section w/o lockdep - * @s: pointer to seqcount_t - * Returns: count to be passed to read_seqcount_retry + * raw_read_seqcount_begin() - start seq-read critical section w/o lockdep + * @s: Pointer to &typedef seqcount_t + * Returns: count to be passed to read_seqcount_retry() * * raw_read_seqcount_begin opens a read critical section of the given * seqcount, but without any lockdep checking. Validity of the critical - * section is tested by checking read_seqcount_retry function. + * section is tested by calling read_seqcount_retry(). */ static inline unsigned raw_read_seqcount_begin(const seqcount_t *s) { @@ -142,13 +150,13 @@ static inline unsigned raw_read_seqcount_begin(const seqcount_t *s) } /** - * read_seqcount_begin - begin a seq-read critical section - * @s: pointer to seqcount_t - * Returns: count to be passed to read_seqcount_retry + * read_seqcount_begin() - begin a seq-read critical section + * @s: Pointer to &typedef seqcount_t + * Returns: count to be passed to read_seqcount_retry() * - * read_seqcount_begin opens a read critical section of the given seqcount. - * Validity of the critical section is tested by checking read_seqcount_retry - * function. + * read_seqcount_begin opens a read critical section of the given + * seqcount_t. Validity of the critical section is tested by calling + * read_seqcount_retry(). */ static inline unsigned read_seqcount_begin(const seqcount_t *s) { @@ -157,8 +165,8 @@ static inline unsigned read_seqcount_begin(const seqcount_t *s) } /** - * raw_seqcount_begin - begin a seq-read critical section - * @s: pointer to seqcount_t + * raw_seqcount_begin() - begin a seq-read critical section + * @s: Pointer to &typedef seqcount_t * Returns: count to be passed to read_seqcount_retry * * raw_seqcount_begin opens a read critical section of the given seqcount. @@ -178,8 +186,8 @@ static inline unsigned raw_seqcount_begin(const seqcount_t *s) } /** - * __read_seqcount_retry - end a seq-read critical section (without barrier) - * @s: pointer to seqcount_t + * __read_seqcount_retry() - end a seq-read critical section (without barrier) + * @s: Pointer to &typedef seqcount_t * @start: count, from read_seqcount_begin * Returns: 1 if retry is required, else 0 * @@ -197,8 +205,8 @@ static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start) } /** - * read_seqcount_retry - end a seq-read critical section - * @s: pointer to seqcount_t + * read_seqcount_retry() - end a seq-read critical section + * @s: Pointer to &typedef seqcount_t * @start: count, from read_seqcount_begin * Returns: 1 if retry is required, else 0 * @@ -225,8 +233,8 @@ static inline void raw_write_seqcount_end(seqcount_t *s) } /** - * raw_write_seqcount_barrier - do a seq write barrier - * @s: pointer to seqcount_t + * raw_write_seqcount_barrier() - do a seq write barrier + * @s: Pointer to &typedef seqcount_t * * This can be used to provide an ordering guarantee instead of the * usual consistency guarantee. It is one wmb cheaper, because we can @@ -267,6 +275,21 @@ static inline void raw_write_seqcount_barrier(seqcount_t *s) s->sequence++; } +/** + * raw_read_seqcount_latch() - pick even or odd seqcount latch data copy + * @s: Pointer to &typedef seqcount_t + * + * Use seqcount latching to switch between two storage places with + * sequence protection to allow interruptible, preemptible, writer + * sections. + * + * Check raw_write_seqcount_latch() for more details and a full reader + * and writer usage example. + * + * Return: sequence counter. Use the lowest bit as index for picking + * which data copy to read. Full counter must then be passed to + * read_seqcount_retry(). + */ static inline int raw_read_seqcount_latch(seqcount_t *s) { /* Pairs with the first smp_wmb() in raw_write_seqcount_latch() */ @@ -275,8 +298,8 @@ static inline int raw_read_seqcount_latch(seqcount_t *s) } /** - * raw_write_seqcount_latch - redirect readers to even/odd copy - * @s: pointer to seqcount_t + * raw_write_seqcount_latch() - redirect readers to even/odd copy + * @s: Pointer to &typedef seqcount_t * * The latch technique is a multiversion concurrency control method that allows * queries during non-atomic modifications. If you can guarantee queries never @@ -336,8 +359,8 @@ static inline int raw_read_seqcount_latch(seqcount_t *s) * idx = seq & 0x01; * entry = data_query(latch->data[idx], ...); * - * smp_rmb(); - * } while (seq != latch->seq); + * // read_seqcount_retry() includes necessary smp_rmb() + * } while (read_seqcount_retry(&latch->seq, seq); * * return entry; * } @@ -391,11 +414,26 @@ static inline void __write_seqcount_begin(seqcount_t *s) __write_seqcount_begin_nested(s, 0); } +/** + * write_seqcount_begin() - start a seqcount write-side critical section + * @s: Pointer to &typedef seqcount_t + * + * write_seqcount_begin opens a write-side critical section of the given + * seqcount. Seqcount write-side critical sections must be externally + * serialized and non-preemptible. + */ static inline void write_seqcount_begin(seqcount_t *s) { write_seqcount_begin_nested(s, 0); } +/** + * write_seqcount_end() - end a seqcount write-side critical section + * @s: Pointer to &typedef seqcount_t + * + * write_seqcount_end closes a write-side critical section of the given + * seqcount. + */ static inline void write_seqcount_end(seqcount_t *s) { seqcount_release(&s->dep_map, _RET_IP_); @@ -403,8 +441,8 @@ static inline void write_seqcount_end(seqcount_t *s) } /** - * write_seqcount_invalidate - invalidate in-progress read-side seq operations - * @s: pointer to seqcount_t + * write_seqcount_invalidate() - invalidate in-progress read-side seq operations + * @s: Pointer to &typedef seqcount_t * * After write_seqcount_invalidate, no read-side seq operations will complete * successfully and see data older than this. @@ -435,32 +473,68 @@ typedef struct { .lock = __SPIN_LOCK_UNLOCKED(lockname) \ } -#define seqlock_init(x) \ +/** + * seqlock_init() - dynamic initializer for seqlock_t + * @sl: Pointer to the seqlock_t instance + */ +#define seqlock_init(sl) \ do { \ - seqcount_init(&(x)->seqcount); \ - spin_lock_init(&(x)->lock); \ + seqcount_init(&(sl)->seqcount); \ + spin_lock_init(&(sl)->lock); \ } while (0) -#define DEFINE_SEQLOCK(x) \ - seqlock_t x = __SEQLOCK_UNLOCKED(x) +/** + * DEFINE_SEQLOCK() - Define a statically-allocated seqlock_t + * @sl: Name of the &typedef seqlock_t instance + */ +#define DEFINE_SEQLOCK(sl) \ + seqlock_t sl = __SEQLOCK_UNLOCKED(sl) -/* - * Read side functions for starting and finalizing a read side section. +/** + * read_seqbegin() - start a seqlock_t read-side critical section + * @sl: Pointer to &typedef seqlock_t + * + * read_seqbegin opens a read side critical section of the given + * seqlock_t. Validity of the critical section is tested by checking + * read_seqretry(). + * + * Return: count to be passed to read_seqretry() */ static inline unsigned read_seqbegin(const seqlock_t *sl) { return read_seqcount_begin(&sl->seqcount); } +/** + * read_seqretry() - end a seqlock_t read side critical section + * @sl: Pointer to &typedef seqlock_t + * @start: count, from read_seqbegin() + * + * read_seqretry closes a read side critical section of the given + * seqlock_t. If the read side critical section was invalid, it must be + * ignored and retried. + * + * Return: 1 if a retry is required, 0 otherwise + */ static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start) { return read_seqcount_retry(&sl->seqcount, start); } -/* - * Lock out other writers and update the count. - * Acts like a normal spin_lock/unlock. - * Don't need preempt_disable() because that is in the spin_lock already. +/** + * write_seqlock() - start a seqlock_t write side critical section + * @sl: Pointer to &typedef seqlock_t + * + * write_seqlock opens a write side critical section of the given + * seqlock_t. It also acquires the spinlock embedded inside the + * sequential lock. All seqlock_t write side critical sections are thus + * automatically serialized and non-preemptible. + * + * If the seqlock_t read side section can be invoked from a hardirq or + * softirq context, the ``_irqsave`` and ``_bh`` variants of this + * function must be respectively used instead. + * + * The opened write side section must be closed with write_sequnlock(). */ static inline void write_seqlock(seqlock_t *sl) { @@ -468,30 +542,74 @@ static inline void write_seqlock(seqlock_t *sl) __write_seqcount_begin(&sl->seqcount); } +/** + * write_sequnlock() - end a seqlock_t write side critical section + * @sl: Pointer to &typedef seqlock_t + * + * write_sequnlock closes the (serialized and non-preemptible) write + * side critical section of the given seqlock_t. + */ static inline void write_sequnlock(seqlock_t *sl) { write_seqcount_end(&sl->seqcount); spin_unlock(&sl->lock); } +/** + * write_seqlock_bh() - start a softirqs-disabled seqlock_t write section + * @sl: Pointer to &typedef seqlock_t + * + * write_seqlock_bh is a write_seqlock() variant that disables softirqs + * before opening the serialized seqlock_t write side critical section. + * Use it only if the read side section, or other writers, can be + * invoked from a softirq context. + * + * The opened write section must be closed with write_sequnlock_bh(). + */ static inline void write_seqlock_bh(seqlock_t *sl) { spin_lock_bh(&sl->lock); __write_seqcount_begin(&sl->seqcount); } +/** + * write_sequnlock_bh() - end a softirqs-disabled seqlock_t write section + * @sl: Pointer to &typedef seqlock_t + * + * write_sequnlock_bh closes the serialized, softirqs-disabled, + * seqlock_t write side critical section. It enables softirqs if they + * were already enabled before calling the paired write_seqlock_bh(). + */ static inline void write_sequnlock_bh(seqlock_t *sl) { write_seqcount_end(&sl->seqcount); spin_unlock_bh(&sl->lock); } +/** + * write_seqlock_irq() - start a non-interruptible seqlock_t write side section + * @sl: Pointer to &typedef seqlock_t + * + * write_seqlock_irq is a write_seqlock() variant where hardirqs are + * disabled before opening the serialized and non-preemptible seqlock_t + * write side critical section. + */ static inline void write_seqlock_irq(seqlock_t *sl) { spin_lock_irq(&sl->lock); __write_seqcount_begin(&sl->seqcount); } +/** + * write_sequnlock_irq() - end a non-interruptible seqlock_t write side section + * @sl: Pointer to &typedef seqlock_t + * + * write_sequnlock_irq closes the serialized and non-interruptible write + * side critical section of the given seqlock_t. It enables local + * interrupts afterwards. + * + * The write critical section must've been opened with write_seqlock_irq(). + */ static inline void write_sequnlock_irq(seqlock_t *sl) { write_seqcount_end(&sl->seqcount); @@ -507,9 +625,36 @@ static inline unsigned long __write_seqlock_irqsave(seqlock_t *sl) return flags; } +/** + * write_seqlock_irqsave() - start a non-interruptible seqlock_t write section + * @lock: Pointer to &typedef seqlock_t + * @flags: Stack-allocated storage for saving caller's local interrupt + * state, to be passed to write_sequnlock_irqrestore(). + * + * write_seqlock_irqsave is a write_seqlock() variant where the caller's + * local interrupts state is saved, then local interrupts are disabled, + * before opening the serialized and non-preemptible seqlock_t write + * side critical section. + * + * Use this only if the read side section can be invoked from a hardirq + * context. + * + * The opened write section must be closed with write_sequnlock_irqrestore(). + */ #define write_seqlock_irqsave(lock, flags) \ do { flags = __write_seqlock_irqsave(lock); } while (0) +/** + * write_sequnlock_irqrestore() - end non-interruptible seqlock_t write section + * @sl: Pointer to &typedef seqlock_t + * @flags: Caller's saved interrupt state, from write_seqlock_irqsave() + * + * write_sequnlock_irq closes the serialized and non-interruptible write + * side critical section of the given seqlock_t. It then restores the + * caller's local interrupts saved state. + * + * The write section must've been opened with write_seqlock_irqsave(). + */ static inline void write_sequnlock_irqrestore(seqlock_t *sl, unsigned long flags) { @@ -517,30 +662,61 @@ write_sequnlock_irqrestore(seqlock_t *sl, unsigned long flags) spin_unlock_irqrestore(&sl->lock, flags); } -/* - * A locking reader exclusively locks out other writers and locking readers, - * but doesn't update the sequence number. Acts like a normal spin_lock/unlock. - * Don't need preempt_disable() because that is in the spin_lock already. +/** + * read_seqlock_excl() - begin a seqlock_t locking reader critical section + * @sl: Pointer to &typedef seqlock_t + * + * read_seqlock_excl opens a locking reader critical section for the + * given seqlock_t. A locking reader exclusively locks out other writers + * and other locking readers, but doesn't update the sequence number. + * + * Locking readers act like a normal spin_lock()/spin_unlock(). + * + * The opened read side section must be closed with read_sequnlock_excl(). */ static inline void read_seqlock_excl(seqlock_t *sl) { spin_lock(&sl->lock); } +/** + * read_sequnlock_excl() - end a seqlock_t locking reader critical section + * @sl: Pointer to &typedef seqlock_t + * + * read_sequnlock_excl closes a locking reader critical section. The + * read section must've been opened with read_seqlock_excl(). + */ static inline void read_sequnlock_excl(seqlock_t *sl) { spin_unlock(&sl->lock); } /** - * read_seqbegin_or_lock - begin a sequence number check or locking block - * @lock: sequence lock - * @seq : sequence number to be checked + * read_seqbegin_or_lock() - begin a seqlock_t lockless or locking reader + * @lock: Pointer to &typedef seqlock_t + * @seq : Marker and return parameter. If the passed value is even, the + * reader will become a *lockless* seqlock_t sequence counter reader as + * in read_seqbegin(). If the passed value is odd, the reader will + * become a fully locking reader, as in read_seqlock_excl(). In the + * first call to read_seqbegin_or_lock(), the caller **must** initialize + * and pass an even value in @seq so a lockless read is optimistically + * tried first. * - * First try it once optimistically without taking the lock. If that fails, - * take the lock. The sequence number is also used as a marker for deciding - * whether to be a reader (even) or writer (odd). - * N.B. seq must be initialized to an even number to begin with. + * read_seqbegin_or_lock optimistically tries a lockless seqlock_t + * sequence counter read first. If an odd counter is found, the lockless + * read trial has failed, and the reader transforms to a full seqlock_t + * locking reader as in read_seqlock_excl(). This is typically used to + * avoid lockless seqlock_t readers starvation (too much retry loops) in + * the case of a sharp spike in write activity. + * + * The opened read section must be closed with done_seqretry(). Check + * Documentation/locking/seqlock.rst for template example code. + * + * Return: The read critical section status is returned through @seq, + * which is overloaded as a return parameter. This value must be passed + * to need_seqretry() to check the validity of the tried seqlock_t read + * section. If the read section must be retried, the returned value must + * also be passed to the next iteration of read_seqbegin_or_lock(). */ static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq) { @@ -550,32 +726,98 @@ static inline void read_seqbegin_or_lock(seqlock_t *lock, int *seq) read_seqlock_excl(lock); } +/** + * need_seqretry() - validate seqlock_t "locking or lockless" reader section + * @lock: Pointer to &typedef seqlock_t + * @seq: count, from read_seqbegin_or_lock() + * + * need_seqretry checks if the seqlock_t read-side critical section + * started with read_seqbegin_or_lock() is valid. If it was not, the + * caller must retry the read-side section. + * + * Return: 1 if a retry is required, 0 otherwise + */ static inline int need_seqretry(seqlock_t *lock, int seq) { return !(seq & 1) && read_seqretry(lock, seq); } +/** + * done_seqretry() - end seqlock_t "locking or lockless" reader section + * @lock: Pointer to &typedef seqlock_t + * @seq: count, from read_seqbegin_or_lock() + * + * done_seqretry finishes the seqlock_t read side critical section + * started by read_seqbegin_or_lock(). Before finishing the critical + * section, the validity of the read side section must've been already + * verified with need_seqretry(). + */ static inline void done_seqretry(seqlock_t *lock, int seq) { if (seq & 1) read_sequnlock_excl(lock); } +/** + * read_seqlock_excl_bh() - start a locking reader seqlock_t section + * with softirqs disabled + * @sl: Pointer to &typedef seqlock_t + * + * read_seqlock_excl_bh is a variant of read_seqlock_excl() that saves + * softirqs state, then disables softirqs, before starting the locking + * reader read side section. Only use this variant if the seqlock_t + * write side section, *or other read sections*, can be invoked from a + * softirq context + * + * The opened section must be closed with read_sequnlock_excl_bh(). + */ static inline void read_seqlock_excl_bh(seqlock_t *sl) { spin_lock_bh(&sl->lock); } +/** + * read_sequnlock_excl_bh() - stop a seqlock_t softirq-disabled locking + * reader section + * @sl: Pointer to &typedef seqlock_t + * + * read_sequnlock_excl_bh ends the softirq-disabled seqlock_t locking + * reader read side section. It restores the softirqs state saved by + * read_seqlock_excl_bh() afterwards. + */ static inline void read_sequnlock_excl_bh(seqlock_t *sl) { spin_unlock_bh(&sl->lock); } +/** + * read_seqlock_excl_irq() - start a non-interruptible seqlock_t locking + * reader section + * @sl: Pointer to &typedef seqlock_t + * + * read_seqlock_excl_irq is a variant of read_seqlock_excl() that + * disables interrupts before starting the locking reader read side + * section. Only use this variant if the seqlock_t write side section, + * *or other read sections*, can be invoked from a hardirq context + * + * The opened read section must be closed with read_sequnlock_excl_irq(). + */ static inline void read_seqlock_excl_irq(seqlock_t *sl) { spin_lock_irq(&sl->lock); } +/** + * read_sequnlock_excl_irq() - end an interrupts-disabled seqlock_t + * locking reader section + * @sl: Pointer to &typedef seqlock_t + * + * read_sequnlock_excl_irq ends the interrupts-disabled seqlock_t + * locking reader read side critical section. It enables local + * interrupts afterwards. + * + * The read section must've been started with read_seqlock_excl_irq(). + */ static inline void read_sequnlock_excl_irq(seqlock_t *sl) { spin_unlock_irq(&sl->lock); @@ -589,15 +831,68 @@ static inline unsigned long __read_seqlock_excl_irqsave(seqlock_t *sl) return flags; } +/** + * read_seqlock_excl_irqsave() - start a non-interruptible seqlock_t + * locking reader section + * @lock: Pointer to &typedef seqlock_t + * @flags: Stack-allocated storage for saving caller's local interrupt + * state, to be passed to read_sequnlock_excl_irqrestore(). + * + * read_seqlock_excl_irqsave is a read_seqlock_excl() variant which + * saves the caller's local interrupts state, then disables local + * interrupts, before opening the seqlock_t locking reader critical + * section. + * + * Use this only if the seqlock_t write side critical section, or other + * read side sections, can be invoked from a hardirq context. + * + * The opened locking reader critical section must be closed with + * read_sequnlock_excl_irqrestore(). + */ #define read_seqlock_excl_irqsave(lock, flags) \ do { flags = __read_seqlock_excl_irqsave(lock); } while (0) +/** + * read_sequnlock_excl_irqrestore() - end non-interruptible seqlock_t + * locking reader section + * @sl: Pointer to &typedef seqlock_t + * @flags: Caller's saved interrupt state, from + * read_seqlock_excl_irqsave() + * + * read_sequnlock_excl_irqrestore closes the non-interruptible seqlock_t + * locking reader section. It then restores the caller's local + * interrupts saved state. + * + * The read section must've been opened with read_seqlock_excl_irqsave(). + */ static inline void read_sequnlock_excl_irqrestore(seqlock_t *sl, unsigned long flags) { spin_unlock_irqrestore(&sl->lock, flags); } +/** + * read_seqbegin_or_lock_irqsave() - begin a seqlock_t lockless reader, or + * a non-interruptible locking reader + * @lock: Pointer to &typedef seqlock_t + * @seq: Marker and return parameter. Check read_seqbegin_or_lock(). + * + * read_seqbegin_or_lock_irqsave is a variant of read_seqbegin_or_lock() + * which saves the local interrupts state, then disables local + * interrupts, before opening a seqlock_t *locking reader* critical + * section. + * + * The opened section must be closed with done_seqretry_irqrestore(). + * + * Return: + * + * 1. The saved local interrupts state in case of a locking reader, to + * be passed to done_seqretry_irqrestore(). + * + * 2. The read critical section status, returned through @seq which is + * overloaded as a return parameter. Check read_seqbegin_or_lock() + * for more info. + */ static inline unsigned long read_seqbegin_or_lock_irqsave(seqlock_t *lock, int *seq) { @@ -611,6 +906,19 @@ read_seqbegin_or_lock_irqsave(seqlock_t *lock, int *seq) return flags; } +/** + * done_seqretry_irqrestore() - end a seqlock_t lockless reader, or a + * non-interruptible locking reader section + * @lock: Pointer to &typedef seqlock_t + * @seq: Count, from read_seqbegin_or_lock_irqsave() + * @flags: Caller's saved local interrupt state in case of a locking + * reader, also from read_seqbegin_or_lock_irqsave() + * + * done_seqretry_irqrestore is a variant of done_seqretry() which + * restores the callers saved local interrupts state in case of a + * locking reader. Check done_seqretry() for more information. The read + * section must've been opened with read_seqbegin_or_lock_irqsave(). + */ static inline void done_seqretry_irqrestore(seqlock_t *lock, int seq, unsigned long flags) { -- 2.20.1