From mboxrd@z Thu Jan 1 00:00:00 1970 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 780BE236938; Thu, 12 Dec 2024 16:45:46 +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=1734021946; cv=none; b=odqskBY5IR/5h4jlPRvNMGgBVObWEN+LzCHm+y0Grz+iQiTMThwNPecpu5j42CrUVWWduoOClk2WR5tPPZBCA/wPB8S0nZqvSWYBLNQTzTsZa3eCTYW5FUE49j0TCHa6SERegBuTTQiJcT7GbStfIkseLIhDd6vNmKDgwp/xJp8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734021946; c=relaxed/simple; bh=bzR2wCWl5pC5YIM6HoEzcL36mdNa1Z0B7SdU4T2Uoo8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=V9TCtxHsyPZ6+uG8t1jahYCsfIUeWADdq6kN06hFcfRbyz42wpDe9n0ZkIPXzbh+I/1RHcXpcOuDeKiCw0dvx0yEN1WzkLWuyFw9VtFn/xADIJtIWNFeM3Xuv0qybnUIiO5TDz7F4Vw0OkBgahbyzY/0qxwsoYRgh2RF3tSbx/I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NmqKGJ55; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="NmqKGJ55" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC5B5C4CECE; Thu, 12 Dec 2024 16:45:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1734021946; bh=bzR2wCWl5pC5YIM6HoEzcL36mdNa1Z0B7SdU4T2Uoo8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NmqKGJ55taon4XdIVfWiLhxy5Ibg8ENrXsaMQm2RX7qQPXmTMWEthgk7Gu1hu6sZ6 h6/YTuS4WN4mKBJQE2UMOfRjkkl86duCS36z4omW0zSMbkuNQhqJnjfdw1FVmPUzI4 xt2/ciEiVIWOvYF4U9aLtFyqb4RayHre8LlK2P84= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Peter Zijlstra (Intel)" , Thomas Gleixner , Petr Mladek , Sasha Levin , Michael Kelley Subject: [PATCH 5.15 106/565] seqlock/latch: Provide raw_read_seqcount_latch_retry() Date: Thu, 12 Dec 2024 15:55:01 +0100 Message-ID: <20241212144315.667797021@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241212144311.432886635@linuxfoundation.org> References: <20241212144311.432886635@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra [ Upstream commit d16317de9b412aa7bd3598c607112298e36b4352 ] The read side of seqcount_latch consists of: do { seq = raw_read_seqcount_latch(&latch->seq); ... } while (read_seqcount_latch_retry(&latch->seq, seq)); which is asymmetric in the raw_ department, and sure enough, read_seqcount_latch_retry() includes (explicit) instrumentation where raw_read_seqcount_latch() does not. This inconsistency becomes a problem when trying to use it from noinstr code. As such, fix it by renaming and re-implementing raw_read_seqcount_latch_retry() without the instrumentation. Specifically the instrumentation in question is kcsan_atomic_next(0) in do___read_seqcount_retry(). Loosing this annotation is not a problem because raw_read_seqcount_latch() does not pass through kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX). Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Reviewed-by: Petr Mladek Tested-by: Michael Kelley # Hyper-V Link: https://lore.kernel.org/r/20230519102715.233598176@infradead.org Stable-dep-of: 5c1806c41ce0 ("kcsan, seqlock: Support seqcount_latch_t") Signed-off-by: Sasha Levin --- include/linux/rbtree_latch.h | 2 +- include/linux/seqlock.h | 15 ++++++++------- kernel/printk/printk.c | 2 +- kernel/time/sched_clock.c | 2 +- kernel/time/timekeeping.c | 4 ++-- 5 files changed, 13 insertions(+), 12 deletions(-) diff --git a/include/linux/rbtree_latch.h b/include/linux/rbtree_latch.h index 3d1a9e716b803..6a0999c26c7cf 100644 --- a/include/linux/rbtree_latch.h +++ b/include/linux/rbtree_latch.h @@ -206,7 +206,7 @@ latch_tree_find(void *key, struct latch_tree_root *root, do { seq = raw_read_seqcount_latch(&root->seq); node = __lt_find(key, root, seq & 1, ops->comp); - } while (read_seqcount_latch_retry(&root->seq, seq)); + } while (raw_read_seqcount_latch_retry(&root->seq, seq)); return node; } diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 2c5d0102315d2..97831499d5005 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -675,9 +675,9 @@ typedef struct { * * Return: sequence counter raw value. Use the lowest bit as an index for * picking which data copy to read. The full counter must then be checked - * with read_seqcount_latch_retry(). + * with raw_read_seqcount_latch_retry(). */ -static inline unsigned raw_read_seqcount_latch(const seqcount_latch_t *s) +static __always_inline unsigned raw_read_seqcount_latch(const seqcount_latch_t *s) { /* * Pairs with the first smp_wmb() in raw_write_seqcount_latch(). @@ -687,16 +687,17 @@ static inline unsigned raw_read_seqcount_latch(const seqcount_latch_t *s) } /** - * read_seqcount_latch_retry() - end a seqcount_latch_t read section + * raw_read_seqcount_latch_retry() - end a seqcount_latch_t read section * @s: Pointer to seqcount_latch_t * @start: count, from raw_read_seqcount_latch() * * Return: true if a read section retry is required, else false */ -static inline int -read_seqcount_latch_retry(const seqcount_latch_t *s, unsigned start) +static __always_inline int +raw_read_seqcount_latch_retry(const seqcount_latch_t *s, unsigned start) { - return read_seqcount_retry(&s->seqcount, start); + smp_rmb(); + return unlikely(READ_ONCE(s->seqcount.sequence) != start); } /** @@ -756,7 +757,7 @@ read_seqcount_latch_retry(const seqcount_latch_t *s, unsigned start) * entry = data_query(latch->data[idx], ...); * * // This includes needed smp_rmb() - * } while (read_seqcount_latch_retry(&latch->seq, seq)); + * } while (raw_read_seqcount_latch_retry(&latch->seq, seq)); * * return entry; * } diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 323931ff61191..5e81d2a79d5cc 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -457,7 +457,7 @@ static u64 latched_seq_read_nolock(struct latched_seq *ls) seq = raw_read_seqcount_latch(&ls->latch); idx = seq & 0x1; val = ls->val[idx]; - } while (read_seqcount_latch_retry(&ls->latch, seq)); + } while (raw_read_seqcount_latch_retry(&ls->latch, seq)); return val; } diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c index b1b9b12899f5e..f3657e964616a 100644 --- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -76,7 +76,7 @@ notrace struct clock_read_data *sched_clock_read_begin(unsigned int *seq) notrace int sched_clock_read_retry(unsigned int seq) { - return read_seqcount_latch_retry(&cd.seq, seq); + return raw_read_seqcount_latch_retry(&cd.seq, seq); } unsigned long long notrace sched_clock(void) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 7f755127bee41..07c949c10de28 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -450,7 +450,7 @@ static __always_inline u64 __ktime_get_fast_ns(struct tk_fast *tkf) tkr = tkf->base + (seq & 0x01); now = ktime_to_ns(tkr->base); now += fast_tk_get_delta_ns(tkr); - } while (read_seqcount_latch_retry(&tkf->seq, seq)); + } while (raw_read_seqcount_latch_retry(&tkf->seq, seq)); return now; } @@ -549,7 +549,7 @@ static __always_inline u64 __ktime_get_real_fast(struct tk_fast *tkf, u64 *mono) basem = ktime_to_ns(tkr->base); baser = ktime_to_ns(tkr->base_real); delta = fast_tk_get_delta_ns(tkr); - } while (read_seqcount_latch_retry(&tkf->seq, seq)); + } while (raw_read_seqcount_latch_retry(&tkf->seq, seq)); if (mono) *mono = basem + delta; -- 2.43.0