From nobody Sat Jul 25 04:18:26 2026 Received: from mail.zeus03.de (zeus03.de [194.117.254.33]) (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 B86E83D47D4 for ; Sat, 18 Jul 2026 16:30:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=194.117.254.33 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784392243; cv=none; b=GSctKDEQcZed+SaM/33B7dDUWfgtmEq3/7aS4V7bftMbaRYEpggRxcM69o4EWxlzEvhPsupCRmFcIP9DDh0JVo7bjh/wGrvez4FLC2E3UhIMNCWfhIfy+wpyHa0d/dGV411LcKQl7WZyGwJLkKSy7k/IX6BCs/RPziXfog4ZXDc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784392243; c=relaxed/simple; bh=zXY4szWNyycp/26dnbAw14LSmLq1Nm84Mt8Mi+rNwzk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LSWqOv5WNYmnWmKZbqjtu7mO4A13sSeI5dd9ZWYrWUXYcTl63ZuF4LhPdEtdOF7LYJ72CDlKv4fz7x3zRPDPjSFGDBV9XKPcg6bwo72uiJUdqldXcPwL0R/kWUD5AeVoT6fzLWu02lLZlzdDc0aQnftzL5ElBvgew1WOGUvS/UY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sang-engineering.com; spf=pass smtp.mailfrom=sang-engineering.com; dkim=pass (2048-bit key) header.d=sang-engineering.com header.i=@sang-engineering.com header.b=U6M4NuqJ; arc=none smtp.client-ip=194.117.254.33 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sang-engineering.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sang-engineering.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sang-engineering.com header.i=@sang-engineering.com header.b="U6M4NuqJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= sang-engineering.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; s=k1; bh=XvVPYIu5IJBFa4YggBlNpJtLCUcLtdHOITJmUpwWG5Q=; b=U6M4Nu qJ7lzwZSAK2a6/X3LAE0QMwoH2G9aPxTdBcNkNMIkxRB3RSksC6PhlYdyLzZwCHR 0oPVk3tlHCXjvyHuo0drYbg5CriA/KJxr1Vrx4BJMnpTgQEsR8IoL5HOrA0wIUKL R6ZsmQ6v7ANHIGq6S/U0KzHg+VsJtgq46Amo8O5ln28wPu2hwNnkTz0zl4L7q82e uhZQXl/EabGbHT7rKHz2ic/aYy1muKjxvc2/Sa6LN/3wXj2hNb9UqPtMeTru8QxD 4fT6Em8fJgJIuWyRbT0MdvR6yGFNLonfUpso7vDz6jixcPiXvQqphjpxDg9D4EVx Lkv6Qf4L2CvwiCmA== Received: (qmail 1799917 invoked from network); 18 Jul 2026 18:30:31 +0200 Received: by mail.zeus03.de with ESMTPSA (TLS_AES_256_GCM_SHA384 encrypted, authenticated); 18 Jul 2026 18:30:31 +0200 X-UD-Smtp-Session: l3s3148p1@MU4VMeVWZ2htKXE8 From: Wolfram Sang To: linux-renesas-soc@vger.kernel.org Cc: Matthew Wilcox , linux-kernel@vger.kernel.org, Wolfram Sang , Bjorn Andersson , Baolin Wang , linux-remoteproc@vger.kernel.org Subject: [PATCH v4 1/3] hwspinlock: Convert to XArray Date: Sat, 18 Jul 2026 18:30:21 +0200 Message-ID: <20260718163024.1726-2-wsa+renesas@sang-engineering.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260718163024.1726-1-wsa+renesas@sang-engineering.com> References: <20260718163024.1726-1-wsa+renesas@sang-engineering.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Matthew Wilcox (Oracle)" The radix tree is deprecated. The XArray uses the same data structure with a nicer interface. The hwspinlock_tree_lock is not needed as the spinlock built into the XArray is sufficient for all these cases after we split a larger critical section in hwspin_lock_request_specific() into two smaller ones. Signed-off-by: Matthew Wilcox (Oracle) Co-developed-by: Wolfram Sang Signed-off-by: Wolfram Sang --- drivers/hwspinlock/hwspinlock_core.c | 160 +++++++++++---------------- 1 file changed, 65 insertions(+), 95 deletions(-) diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwsp= inlock_core.c index a509b73da190..e2b7a2271de6 100644 --- a/drivers/hwspinlock/hwspinlock_core.c +++ b/drivers/hwspinlock/hwspinlock_core.c @@ -16,7 +16,7 @@ #include #include #include -#include +#include #include #include #include @@ -27,35 +27,21 @@ /* retry delay used in atomic context */ #define HWSPINLOCK_RETRY_DELAY_US 100 =20 -/* radix tree tags */ -#define HWSPINLOCK_UNUSED (0) /* tags an hwspinlock as unused */ +/* XArray search mark */ +#define HWSPINLOCK_UNUSED XA_MARK_0 /* marks a hwspinlock as unused */ =20 /* - * A radix tree is used to maintain the available hwspinlock instances. + * An XArray is used to maintain the available hwspinlock instances. * The tree associates hwspinlock pointers with their integer key id, * and provides easy-to-use API which makes the hwspinlock core code simple * and easy to read. * - * Radix trees are quick on lookups, and reasonably efficient in terms of + * XArrays are quick on lookups, and reasonably efficient in terms of * storage, especially with high density usages such as this framework * requires (a continuous range of integer keys, beginning with zero, is - * used as the ID's of the hwspinlock instances). - * - * The radix tree API supports tagging items in the tree, which this - * framework uses to mark unused hwspinlock instances (see the - * HWSPINLOCK_UNUSED tag above). As a result, the process of querying the - * tree, looking for an unused hwspinlock instance, is now reduced to a - * single radix tree API call. - */ -static RADIX_TREE(hwspinlock_tree, GFP_KERNEL); - -/* - * Synchronization of access to the tree is achieved using this mutex, - * as the radix-tree API requires that users provide all synchronisation. - * A mutex is needed because we're using non-atomic radix tree allocations. + * used as the ID of the hwspinlock instances). */ -static DEFINE_MUTEX(hwspinlock_tree_lock); - +static DEFINE_XARRAY(hwspinlocks); =20 /** * __hwspin_trylock() - attempt to lock a specific hwspinlock @@ -369,10 +355,9 @@ of_hwspin_lock_simple_xlate(const struct of_phandle_ar= gs *hwlock_spec) */ int of_hwspin_lock_get_id(struct device_node *np, int index) { + XA_STATE(xas, &hwspinlocks, 0); struct of_phandle_args args; struct hwspinlock *hwlock; - struct radix_tree_iter iter; - void **slot; int id; int ret; =20 @@ -389,15 +374,9 @@ int of_hwspin_lock_get_id(struct device_node *np, int = index) /* Find the hwspinlock device: we need its base_id */ ret =3D -EPROBE_DEFER; rcu_read_lock(); - radix_tree_for_each_slot(slot, &hwspinlock_tree, &iter, 0) { - hwlock =3D radix_tree_deref_slot(slot); - if (unlikely(!hwlock)) - continue; - if (radix_tree_deref_retry(hwlock)) { - slot =3D radix_tree_iter_retry(&iter); + xas_for_each(&xas, hwlock, ULONG_MAX) { + if (xas_retry(&xas, hwlock)) continue; - } - if (device_match_of_node(hwlock->bank->dev, args.np)) { ret =3D 0; break; @@ -452,51 +431,50 @@ EXPORT_SYMBOL_GPL(of_hwspin_lock_get_id_byname); =20 static int hwspin_lock_register_single(struct hwspinlock *hwlock, int id) { - struct hwspinlock *tmp; + XA_STATE(xas, &hwspinlocks, id); + struct hwspinlock *existing; int ret; =20 - mutex_lock(&hwspinlock_tree_lock); - - ret =3D radix_tree_insert(&hwspinlock_tree, id, hwlock); - if (ret) { - if (ret =3D=3D -EEXIST) + do { + xas_lock(&xas); + existing =3D xas_load(&xas); + if (existing) { pr_err("hwspinlock id %d already exists!\n", id); - goto out; - } - - /* mark this hwspinlock as available */ - tmp =3D radix_tree_tag_set(&hwspinlock_tree, id, HWSPINLOCK_UNUSED); + xas_set_err(&xas, -EBUSY); + } + xas_store(&xas, hwlock); =20 - /* self-sanity check which should never fail */ - WARN_ON(tmp !=3D hwlock); + /* mark this hwspinlock as available */ + xas_set_mark(&xas, HWSPINLOCK_UNUSED); + ret =3D xas_error(&xas); + xas_unlock(&xas); + } while (xas_nomem(&xas, GFP_KERNEL)); =20 -out: - mutex_unlock(&hwspinlock_tree_lock); return ret; } =20 static struct hwspinlock *hwspin_lock_unregister_single(unsigned int id) { + XA_STATE(xas, &hwspinlocks, id); struct hwspinlock *hwlock =3D NULL; - int ret; + bool unused; =20 - mutex_lock(&hwspinlock_tree_lock); + xas_lock(&xas); + xas_load(&xas); =20 - /* make sure the hwspinlock is not in use (tag is set) */ - ret =3D radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED); - if (ret =3D=3D 0) { + /* make sure the hwspinlock is not in use (mark is set) */ + unused =3D xas_get_mark(&xas, HWSPINLOCK_UNUSED); + if (!unused) { pr_err("hwspinlock %d still in use (or not present)\n", id); goto out; } =20 - hwlock =3D radix_tree_delete(&hwspinlock_tree, id); - if (!hwlock) { - pr_err("failed to delete hwspinlock %d\n", id); - goto out; - } + hwlock =3D xas_store(&xas, NULL); + if (!hwlock) + pr_err("hwspinlock %d already deleted\n", id); =20 out: - mutex_unlock(&hwspinlock_tree_lock); + xas_unlock(&xas); return hwlock; } =20 @@ -666,20 +644,18 @@ int devm_hwspin_lock_register(struct device *dev, EXPORT_SYMBOL_GPL(devm_hwspin_lock_register); =20 /** - * __hwspin_lock_request() - tag an hwspinlock as used and power it up + * hwspin_lock_prepare() - prepare a hwspinlock * @hwlock: the target hwspinlock * * This is an internal function that prepares an hwspinlock instance - * before it is given to the user. The function assumes that - * hwspinlock_tree_lock is taken. + * before it is given to the user. * * Returns: %0 or positive to indicate success, and a negative value to * indicate an error (with the appropriate error code) */ -static int __hwspin_lock_request(struct hwspinlock *hwlock) +static int hwspin_lock_prepare(struct hwspinlock *hwlock) { struct device *dev =3D hwlock->bank->dev; - struct hwspinlock *tmp; int ret; =20 /* prevent underlying implementation from being removed */ @@ -697,16 +673,7 @@ static int __hwspin_lock_request(struct hwspinlock *hw= lock) return ret; } =20 - ret =3D 0; - - /* mark hwspinlock as used, should not fail */ - tmp =3D radix_tree_tag_clear(&hwspinlock_tree, hwlock_to_id(hwlock), - HWSPINLOCK_UNUSED); - - /* self-sanity check that should never fail */ - WARN_ON(tmp !=3D hwlock); - - return ret; + return 0; } =20 /** @@ -724,13 +691,14 @@ static int __hwspin_lock_request(struct hwspinlock *h= wlock) */ struct hwspinlock *hwspin_lock_request_specific(unsigned int id) { + XA_STATE(xas, &hwspinlocks, id); struct hwspinlock *hwlock; + bool unused; int ret; =20 - mutex_lock(&hwspinlock_tree_lock); + xas_lock(&xas); =20 - /* make sure this hwspinlock exists */ - hwlock =3D radix_tree_lookup(&hwspinlock_tree, id); + hwlock =3D xas_load(&xas); if (!hwlock) { pr_warn("hwspinlock %u does not exist\n", id); goto out; @@ -739,21 +707,25 @@ struct hwspinlock *hwspin_lock_request_specific(unsig= ned int id) /* sanity check (this shouldn't happen) */ WARN_ON(hwlock_to_id(hwlock) !=3D id); =20 - /* make sure this hwspinlock is unused */ - ret =3D radix_tree_tag_get(&hwspinlock_tree, id, HWSPINLOCK_UNUSED); - if (ret =3D=3D 0) { + unused =3D xas_get_mark(&xas, HWSPINLOCK_UNUSED); + if (!unused) { pr_warn("hwspinlock %u is already in use\n", id); hwlock =3D NULL; goto out; } =20 - /* mark as used and power up */ - ret =3D __hwspin_lock_request(hwlock); - if (ret < 0) - hwlock =3D NULL; + xas_clear_mark(&xas, HWSPINLOCK_UNUSED); + xas_unlock(&xas); =20 + ret =3D hwspin_lock_prepare(hwlock); + + xas_lock(&xas); + if (ret < 0) { + hwlock =3D NULL; + xas_set_mark(&xas, HWSPINLOCK_UNUSED); + } out: - mutex_unlock(&hwspinlock_tree_lock); + xas_unlock(&xas); return hwlock; } EXPORT_SYMBOL_GPL(hwspin_lock_request_specific); @@ -772,9 +744,10 @@ EXPORT_SYMBOL_GPL(hwspin_lock_request_specific); */ int hwspin_lock_free(struct hwspinlock *hwlock) { + XA_STATE(xas, &hwspinlocks, 0); struct device *dev; - struct hwspinlock *tmp; - int ret; + bool unused; + int ret =3D 0; =20 if (!hwlock) { pr_err("invalid hwlock\n"); @@ -782,12 +755,13 @@ int hwspin_lock_free(struct hwspinlock *hwlock) } =20 dev =3D hwlock->bank->dev; - mutex_lock(&hwspinlock_tree_lock); + xas_lock(&xas); + xas_set(&xas, hwlock_to_id(hwlock)); + xas_load(&xas); =20 /* make sure the hwspinlock is used */ - ret =3D radix_tree_tag_get(&hwspinlock_tree, hwlock_to_id(hwlock), - HWSPINLOCK_UNUSED); - if (ret =3D=3D 1) { + unused =3D xas_get_mark(&xas, HWSPINLOCK_UNUSED); + if (unused) { dev_err(dev, "%s: hwlock is already free\n", __func__); dump_stack(); ret =3D -EINVAL; @@ -798,16 +772,12 @@ int hwspin_lock_free(struct hwspinlock *hwlock) pm_runtime_put(dev); =20 /* mark this hwspinlock as available */ - tmp =3D radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock), - HWSPINLOCK_UNUSED); - - /* sanity check (this shouldn't happen) */ - WARN_ON(tmp !=3D hwlock); + xas_set_mark(&xas, HWSPINLOCK_UNUSED); =20 module_put(dev->driver->owner); =20 out: - mutex_unlock(&hwspinlock_tree_lock); + xas_unlock(&xas); return ret; } EXPORT_SYMBOL_GPL(hwspin_lock_free); --=20 2.51.0 From nobody Sat Jul 25 04:18:26 2026 Received: from mail.zeus03.de (zeus03.de [194.117.254.33]) (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 84FF12C86D for ; Sat, 18 Jul 2026 16:30:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=194.117.254.33 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784392243; 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spf=pass smtp.mailfrom=sang-engineering.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sang-engineering.com header.i=@sang-engineering.com header.b="XwcdYU2u" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= sang-engineering.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; s=k1; bh=6fuvpky/vj2k5JeMwrjaeyYY7HfOB3M6cQnDR7IDEgQ=; b=XwcdYU 2uvCIlqZeWaf/DYDtN8px+QmUlhbi8FtMuC1z/uwxY6G/sKVzlHM7A1yxRf40bSa g9l7mq37JDopsmiuTjYCIsBMfQzWfw1x8/srlbxHrvuPQIeM3FRowBm/gsT+aLmM gxjOVyLtDsG1FJHV2j6htthNoKhIEjTNODq5IZ/KAzcOPNBXQJHhLb+aN52PzbIj BNOvAXcYFP80ndeUjj6SoWWwAHir0BLX3eWJ4xG/ZiJgBLk0y3tZ0+typ17EauPY 1uch9r5vFsOeciULIDL7BUCN6skj4TEJ6W9AWCvYVBcqCpSkdXb5VysNGd+VHkDX nqAb8Ta/OHqaRTtQ== Received: (qmail 1799972 invoked from network); 18 Jul 2026 18:30:32 +0200 Received: by mail.zeus03.de with ESMTPSA (TLS_AES_256_GCM_SHA384 encrypted, authenticated); 18 Jul 2026 18:30:32 +0200 X-UD-Smtp-Session: l3s3148p1@3+wlMeVWAiJtKXE8 From: Wolfram Sang To: linux-renesas-soc@vger.kernel.org Cc: Matthew Wilcox , linux-kernel@vger.kernel.org, Wolfram Sang , Bjorn Andersson , Baolin Wang , linux-remoteproc@vger.kernel.org Subject: [PATCH v4 2/3] hwspinlock: add list of mailboxes to debugfs Date: Sat, 18 Jul 2026 18:30:22 +0200 Message-ID: <20260718163024.1726-3-wsa+renesas@sang-engineering.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260718163024.1726-1-wsa+renesas@sang-engineering.com> References: <20260718163024.1726-1-wsa+renesas@sang-engineering.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" To help debugging, offer a list of registered hwspinlocks in debugfs. It will also print the responsible hwspinlock_device and if the spinlock is currently used. It does not show if the lock is taken because of side-effects. Often, reading a lock means actually taking it. Signed-off-by: Wolfram Sang --- drivers/hwspinlock/hwspinlock_core.c | 67 ++++++++++++++++++++++++++++ 1 file changed, 67 insertions(+) diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwsp= inlock_core.c index e2b7a2271de6..84e9aae6ef44 100644 --- a/drivers/hwspinlock/hwspinlock_core.c +++ b/drivers/hwspinlock/hwspinlock_core.c @@ -9,6 +9,7 @@ =20 #define pr_fmt(fmt) "%s: " fmt, __func__ =20 +#include #include #include #include @@ -21,6 +22,7 @@ #include #include #include +#include =20 #include "hwspinlock_internal.h" =20 @@ -858,5 +860,70 @@ struct hwspinlock *devm_hwspin_lock_request_specific(s= truct device *dev, } EXPORT_SYMBOL_GPL(devm_hwspin_lock_request_specific); =20 +#ifdef CONFIG_DEBUG_FS +static void *hwspin_lock_seq_start(struct seq_file *s, loff_t *ppos) +{ + unsigned long index =3D *ppos; + struct hwspinlock *hwlock; + + rcu_read_lock(); + hwlock =3D xa_find(&hwspinlocks, &index, ULONG_MAX, XA_PRESENT); + *ppos =3D index; + + return hwlock; +} + +static void *hwspin_lock_seq_next(struct seq_file *s, void *v, loff_t *ppo= s) +{ + /* Increase ppos here to avoid endless loops. Don't use xa_find_after() */ + unsigned long index =3D *ppos + 1; + struct hwspinlock *hwlock; + + hwlock =3D xa_find(&hwspinlocks, &index, ULONG_MAX, XA_PRESENT); + *ppos =3D index; + + return hwlock; +} + +static void hwspin_lock_seq_stop(struct seq_file *s, void *v) +{ + rcu_read_unlock(); +} + +static int hwspin_lock_seq_show(struct seq_file *s, void *v) +{ + struct hwspinlock *hwlock =3D v; + bool unused =3D xa_get_mark(&hwspinlocks, s->index, HWSPINLOCK_UNUSED); + + seq_printf(s, "%4llu:\t%s\t%s\n", s->index, unused ? "free" : "in use", + dev_name(hwlock->bank->dev)); + return 0; +} + +static const struct seq_operations hwspinlock_sops =3D { + .start =3D hwspin_lock_seq_start, + .next =3D hwspin_lock_seq_next, + .stop =3D hwspin_lock_seq_stop, + .show =3D hwspin_lock_seq_show, +}; +DEFINE_SEQ_ATTRIBUTE(hwspinlock); + +/* + * subsys_initcall() is used here but controllers may already have been + * registered earlier or will be later. The rationale is that debugfs is + * accessed only late, i.e. from userspace. So, files created here must ma= ke no + * assumptions about initcall ordering. + */ +static int __init hwspin_lock_init(void) +{ + struct dentry *hwspinlock_debugfs =3D debugfs_create_dir("hwspinlock", NU= LL); + + debugfs_create_file("hwspinlock_summary", 0444, hwspinlock_debugfs, + NULL, &hwspinlock_fops); + return 0; +} +subsys_initcall(hwspin_lock_init); +#endif /* DEBUG_FS */ + MODULE_DESCRIPTION("Hardware spinlock interface"); MODULE_AUTHOR("Ohad Ben-Cohen "); --=20 2.51.0 From nobody Sat Jul 25 04:18:26 2026 Received: from mail.zeus03.de (zeus03.de [194.117.254.33]) (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 0E3173D969E for ; Sat, 18 Jul 2026 16:30:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=194.117.254.33 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784392243; cv=none; b=ic81rBS65uz/EGXuV9XwAy9qkEC37s381wSjUT4hvDILasPVtcviKzegFH2sOBSqZhtc+pUWyuylTffGpr0yjacvpM3/ixjQuv8QwkIKEPgaxgQoGoBUaS6zbEcgU/7povFvxb+RF73veTTTEYolG5+BJwnhBdS1M/3PXlM6hmo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784392243; c=relaxed/simple; bh=Lk0wHwpMctVi3g53dFX1WZLpEkGHY4JTmAb6KBR6f+I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GT4/DuC0X9bN65xcQTgLK7k9occmSgOKkxKwH2DFMywKDiXVwKHgra0ytvv3ee400AioZJbdOVUBXth8HsGInMAehc5eb3UUvXaOhGC6Vve8iJOA6EkNoR7ZpW/JlIjb9P+zyL5cpK0vwoyyGNY3/9AXWiYDx5Td3AbzDUPkbS4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sang-engineering.com; spf=pass smtp.mailfrom=sang-engineering.com; dkim=pass (2048-bit key) header.d=sang-engineering.com header.i=@sang-engineering.com header.b=QzW/2PSo; arc=none smtp.client-ip=194.117.254.33 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sang-engineering.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sang-engineering.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sang-engineering.com header.i=@sang-engineering.com header.b="QzW/2PSo" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= sang-engineering.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; s=k1; bh=1Pl172FVFj5opAt6Zg77g7wc2kZredW5bXE1qf5TaBk=; b=QzW/2P SoxHNiUg7fVRvfhophUslxFYbtUEVSyQCnSvi4CYs705OmJlwdfoHPwntGKX4nPD nhB0JrweqsMAr4ec2p5tyXP5JzgAoj3R8Z9X0UmbemkChvgSdtoL8H+OLVy0dCcp JvXhMaezFBA72Quw7of3ffIqlz9aYHcB9e59g0XkzAsPeEkUIKxRySJ4Iaq4NvYC 763qhuESRAcxPICmIK8YLlvFdlbaw96XKCtKH5gDO5YZDGuZLnpiPufoHbxqcqK0 al7GF/kqu9RlnyVyo+kqjkbIVPHnpEDs6ZVyGxZgTb4iuO+YXcc+9eL4L9SFP2sV tluHP6vuO+IOI68w== Received: (qmail 1800012 invoked from network); 18 Jul 2026 18:30:33 +0200 Received: by mail.zeus03.de with ESMTPSA (TLS_AES_256_GCM_SHA384 encrypted, authenticated); 18 Jul 2026 18:30:33 +0200 X-UD-Smtp-Session: l3s3148p1@hLs3MeVW6FdtKXE8 From: Wolfram Sang To: linux-renesas-soc@vger.kernel.org Cc: Matthew Wilcox , linux-kernel@vger.kernel.org, Wolfram Sang , Bjorn Andersson , Baolin Wang , linux-remoteproc@vger.kernel.org Subject: [PATCH v4 3/3] hwspinlock: add low level debug capabilities Date: Sat, 18 Jul 2026 18:30:23 +0200 Message-ID: <20260718163024.1726-4-wsa+renesas@sang-engineering.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260718163024.1726-1-wsa+renesas@sang-engineering.com> References: <20260718163024.1726-1-wsa+renesas@sang-engineering.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" While developing the hwspinlock core or a device driver, it can be really helpful to change states from userspace. Add a debugsfs interface to request, free, lock, unlock, and test hwspinlocks. Because this is a potentially dangerous interface, it can only be enabled via source code. Similar to writeable attributes for clocks where this idea stems from. The created files take a single id for a single lock. To test all locks in a system, one could use this oneliner while in the debugfs directory: for l in $(cut -d: -f1 hwspinlock_summary); do echo $l > test_lock; done Signed-off-by: Wolfram Sang --- drivers/hwspinlock/hwspinlock_core.c | 122 +++++++++++++++++++++++++++ 1 file changed, 122 insertions(+) diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwsp= inlock_core.c index 84e9aae6ef44..052dea7e4850 100644 --- a/drivers/hwspinlock/hwspinlock_core.c +++ b/drivers/hwspinlock/hwspinlock_core.c @@ -908,6 +908,110 @@ static const struct seq_operations hwspinlock_sops = =3D { }; DEFINE_SEQ_ATTRIBUTE(hwspinlock); =20 +/* + * This can be dangerous, therefore don't provide any real compile time + * configuration option for this feature. + * People who want to use this will need to modify the source code directl= y. + */ +#undef HWSPINLOCK_LOW_LEVEL_DEBUG +#ifdef HWSPINLOCK_LOW_LEVEL_DEBUG + +static struct hwspinlock *hwspin_lock_ll_debug_get(u64 id) +{ + struct hwspinlock *hwlock; + unsigned long index =3D id; + + rcu_read_lock(); + hwlock =3D xa_find(&hwspinlocks, &index, ULONG_MAX, XA_PRESENT); + rcu_read_unlock(); + + return hwlock; +} + +static int fops_request_set(void *data, u64 id) +{ + struct hwspinlock *hwlock =3D hwspin_lock_request_specific(id); + + return hwlock ? 0 : -ENOENT; +} +DEFINE_DEBUGFS_ATTRIBUTE(fops_request, NULL, fops_request_set, "%llu\n"); + +static int fops_free_set(void *data, u64 id) +{ + struct hwspinlock *hwlock =3D hwspin_lock_ll_debug_get(id); + + return hwlock ? hwspin_lock_free(hwlock) : -ENOENT; +} +DEFINE_DEBUGFS_ATTRIBUTE(fops_free, NULL, fops_free_set, "%llu\n"); + +/* + * It is intentionally allowed to lock/free hwspinlocks which have not been + * requested before. Like error injection, these inconsistent states can be + * very useful for debugging. + */ +static int fops_trylock_raw_set(void *data, u64 id) +{ + struct hwspinlock *hwlock =3D hwspin_lock_ll_debug_get(id); + + return hwlock ? hwspin_trylock_raw(hwlock) : -ENOENT; +} +DEFINE_DEBUGFS_ATTRIBUTE(fops_trylock_raw, NULL, fops_trylock_raw_set, "%l= lu\n"); + +static int fops_unlock_raw_set(void *data, u64 id) +{ + struct hwspinlock *hwlock =3D hwspin_lock_ll_debug_get(id); + + if (hwlock) + hwspin_unlock_raw(hwlock); + + return 0; +} +DEFINE_DEBUGFS_ATTRIBUTE(fops_unlock_raw, NULL, fops_unlock_raw_set, "%llu= \n"); + +static int fops_test_set(void *data, u64 id) +{ + struct hwspinlock *hwlock =3D hwspin_lock_request_specific(id); + int ret; + + if (!hwlock) + return -ENOENT; + + /* Try twice to see if unlocking was also successful */ + for (int i =3D 0; i < 2; i++) { + ret =3D hwspin_trylock(hwlock); + if (ret) { + hwspin_lock_free(hwlock); + return ret; + } + + ret =3D hwspin_trylock(hwlock); + if (ret !=3D -EBUSY) { + hwspin_lock_free(hwlock); + return -EACCES; + } + + hwspin_unlock(hwlock); + } + + ret =3D hwspin_lock_free(hwlock); + if (ret) + return ret; + + pr_info("Successfully tested lock %llu\n", id); + return 0; +} +DEFINE_DEBUGFS_ATTRIBUTE(fops_test, NULL, fops_test_set, "%llu\n"); + +static void hwspin_lock_low_level_debug_init(struct dentry *rootdir) +{ + debugfs_create_file("request", 0200, rootdir, NULL, &fops_request); + debugfs_create_file("free", 0200, rootdir, NULL, &fops_free); + debugfs_create_file("lock", 0200, rootdir, NULL, &fops_trylock_raw); + debugfs_create_file("unlock", 0200, rootdir, NULL, &fops_unlock_raw); + debugfs_create_file("test_lock", 0200, rootdir, NULL, &fops_test); +} +#endif + /* * subsys_initcall() is used here but controllers may already have been * registered earlier or will be later. The rationale is that debugfs is @@ -920,6 +1024,24 @@ static int __init hwspin_lock_init(void) =20 debugfs_create_file("hwspinlock_summary", 0444, hwspinlock_debugfs, NULL, &hwspinlock_fops); + +#ifdef HWSPINLOCK_LOW_LEVEL_DEBUG + pr_warn("**********************************************************\n"); + pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n"); + pr_warn("** **\n"); + pr_warn("** Low Level Debug for hwspinlocks is compiled in! **\n"); + pr_warn("** **\n"); + pr_warn("** This means safety, security, stability can be easily **\n"); + pr_warn("** compromised from userspace! **\n"); + pr_warn("** **\n"); + pr_warn("** If you see this message and you are not debugging **\n"); + pr_warn("** the kernel, report this immediately to your vendor! **\n"); + pr_warn("** **\n"); + pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n"); + pr_warn("**********************************************************\n"); + hwspin_lock_low_level_debug_init(hwspinlock_debugfs); +#endif + return 0; } subsys_initcall(hwspin_lock_init); --=20 2.51.0