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 D1F138120A; Sun, 24 Mar 2024 22:48:46 +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=1711320527; cv=none; b=X1NvMg9/wJ+0v+Z/XNh8COO2BJtfmybYzdqo30G8jXU8FnBifQXwjAJEKJx1QPP4uYFN1vGoSfjRBEv6NlQomq1WQrKO8L1n7poZPDz4XV2lI9XnoATrR/2yNlJFoOHFQd0bnW0kiswLgqBAYwhN9l4NAluuI1IgDJ+CzaGplHE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711320527; c=relaxed/simple; bh=OpbSXIs9k98gbYogvjWK31VrjqjDrXBfziuOBKHJiw4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DuaFNUnZr4Ugd6n/KiXORrsl7iBYYk4UuCWI0P5z2MOXXMfrasz/SBy/JKyIGe29b2wXNSVCb2/N/UFEZo+T4w+ld2WLioKdRWi2YmfXO3vmx4j7ODrbfvEh299seUxboN7tuEgkY892kxYQJPfklXQkWrD6MI65bvKAXgdtxjY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OFTcr+OU; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OFTcr+OU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1CC93C433C7; Sun, 24 Mar 2024 22:48:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711320526; bh=OpbSXIs9k98gbYogvjWK31VrjqjDrXBfziuOBKHJiw4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OFTcr+OUneQA9qpVMqeSPRz8LJIuvl+AHVkz6vLnSYewPyA7Ye8fftWLn4YADaT0d NGEC+rPNgOabG//TB4pLTtNcIrplfHRMjp9MCfaqbydoT1jwEnbIGp2jaLDZsZ+zYg /YGI+j3I3VPdlLI+1UoT/lqX0WnfWNRJDuoY2C+zmQrt20NsXmpr5YDOOm2A4JNu9z bhwp0MJlTIEPZXo/vdf+Efa83131vZ2y+r/tSB393rJs1/ujU1H0C5GrkIA8ufv2JC tvL5BdRMPHV0z60L20xPu0Xdc/Ne+ll0bD/n6v2Dlqv6KgIR4Ga5LuMB7rFdDQ4tP/ CzdZCy9pmeRdg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Tejun Heo , Lai Jiangshan , Sasha Levin Subject: [PATCH 6.7 088/713] workqueue: RCU protect wq->dfl_pwq and implement accessors for it Date: Sun, 24 Mar 2024 18:36:54 -0400 Message-ID: <20240324224720.1345309-89-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324224720.1345309-1-sashal@kernel.org> References: <20240324224720.1345309-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Tejun Heo [ Upstream commit 9f66cff212bb3c1cd25996aaa0dfd0c9e9d8baab ] wq->cpu_pwq is RCU protected but wq->dfl_pwq isn't. This is okay because currently wq->dfl_pwq is used only accessed to install it into wq->cpu_pwq which doesn't require RCU access. However, we want to be able to access wq->dfl_pwq under RCU in the future to access its __pod_cpumask and the code can be made easier to read by making the two pwq fields behave in the same way. - Make wq->dfl_pwq RCU protected. - Add unbound_pwq_slot() and unbound_pwq() which can access both ->dfl_pwq and ->cpu_pwq. The former returns the double pointer that can be used access and update the pwqs. The latter performs locking check and dereferences the double pointer. - pwq accesses and updates are converted to use unbound_pwq[_slot](). Signed-off-by: Tejun Heo Reviewed-by: Lai Jiangshan Stable-dep-of: 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues") Signed-off-by: Sasha Levin --- kernel/workqueue.c | 64 +++++++++++++++++++++++++++++----------------- 1 file changed, 40 insertions(+), 24 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 059f122563def..53bebd8c8b457 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -304,7 +304,7 @@ struct workqueue_struct { int saved_max_active; /* WQ: saved max_active */ struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */ - struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */ + struct pool_workqueue __rcu *dfl_pwq; /* PW: only for unbound wqs */ #ifdef CONFIG_SYSFS struct wq_device *wq_dev; /* I: for sysfs interface */ @@ -629,6 +629,23 @@ static int worker_pool_assign_id(struct worker_pool *pool) return ret; } +static struct pool_workqueue __rcu ** +unbound_pwq_slot(struct workqueue_struct *wq, int cpu) +{ + if (cpu >= 0) + return per_cpu_ptr(wq->cpu_pwq, cpu); + else + return &wq->dfl_pwq; +} + +/* @cpu < 0 for dfl_pwq */ +static struct pool_workqueue *unbound_pwq(struct workqueue_struct *wq, int cpu) +{ + return rcu_dereference_check(*unbound_pwq_slot(wq, cpu), + lockdep_is_held(&wq_pool_mutex) || + lockdep_is_held(&wq->mutex)); +} + static unsigned int work_color_to_flags(int color) { return color << WORK_STRUCT_COLOR_SHIFT; @@ -4318,10 +4335,11 @@ static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu, "possible intersect\n"); } -/* install @pwq into @wq's cpu_pwq and return the old pwq */ +/* install @pwq into @wq and return the old pwq, @cpu < 0 for dfl_pwq */ static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq, int cpu, struct pool_workqueue *pwq) { + struct pool_workqueue __rcu **slot = unbound_pwq_slot(wq, cpu); struct pool_workqueue *old_pwq; lockdep_assert_held(&wq_pool_mutex); @@ -4330,8 +4348,8 @@ static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq, /* link_pwq() can handle duplicate calls */ link_pwq(pwq); - old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu)); - rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq); + old_pwq = rcu_access_pointer(*slot); + rcu_assign_pointer(*slot, pwq); return old_pwq; } @@ -4431,14 +4449,11 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx) copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs); - /* save the previous pwq and install the new one */ + /* save the previous pwqs and install the new ones */ for_each_possible_cpu(cpu) ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu, ctx->pwq_tbl[cpu]); - - /* @dfl_pwq might not have been used, ensure it's linked */ - link_pwq(ctx->dfl_pwq); - swap(ctx->wq->dfl_pwq, ctx->dfl_pwq); + ctx->dfl_pwq = install_unbound_pwq(ctx->wq, -1, ctx->dfl_pwq); mutex_unlock(&ctx->wq->mutex); } @@ -4561,9 +4576,7 @@ static void wq_update_pod(struct workqueue_struct *wq, int cpu, /* nothing to do if the target cpumask matches the current pwq */ wq_calc_pod_cpumask(target_attrs, cpu, off_cpu); - pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu), - lockdep_is_held(&wq_pool_mutex)); - if (wqattrs_equal(target_attrs, pwq->pool->attrs)) + if (wqattrs_equal(target_attrs, unbound_pwq(wq, cpu)->pool->attrs)) return; /* create a new pwq */ @@ -4581,10 +4594,11 @@ static void wq_update_pod(struct workqueue_struct *wq, int cpu, use_dfl_pwq: mutex_lock(&wq->mutex); - raw_spin_lock_irq(&wq->dfl_pwq->pool->lock); - get_pwq(wq->dfl_pwq); - raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock); - old_pwq = install_unbound_pwq(wq, cpu, wq->dfl_pwq); + pwq = unbound_pwq(wq, -1); + raw_spin_lock_irq(&pwq->pool->lock); + get_pwq(pwq); + raw_spin_unlock_irq(&pwq->pool->lock); + old_pwq = install_unbound_pwq(wq, cpu, pwq); out_unlock: mutex_unlock(&wq->mutex); put_pwq_unlocked(old_pwq); @@ -4622,10 +4636,13 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq) cpus_read_lock(); if (wq->flags & __WQ_ORDERED) { + struct pool_workqueue *dfl_pwq; + ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]); /* there should only be single pwq for ordering guarantee */ - WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node || - wq->pwqs.prev != &wq->dfl_pwq->pwqs_node), + dfl_pwq = rcu_access_pointer(wq->dfl_pwq); + WARN(!ret && (wq->pwqs.next != &dfl_pwq->pwqs_node || + wq->pwqs.prev != &dfl_pwq->pwqs_node), "ordering guarantee broken for workqueue %s\n", wq->name); } else { ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]); @@ -4856,7 +4873,7 @@ static bool pwq_busy(struct pool_workqueue *pwq) if (pwq->nr_in_flight[i]) return true; - if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1)) + if ((pwq != rcu_access_pointer(pwq->wq->dfl_pwq)) && (pwq->refcnt > 1)) return true; if (!pwq_is_empty(pwq)) return true; @@ -4940,13 +4957,12 @@ void destroy_workqueue(struct workqueue_struct *wq) rcu_read_lock(); for_each_possible_cpu(cpu) { - pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu)); - RCU_INIT_POINTER(*per_cpu_ptr(wq->cpu_pwq, cpu), NULL); - put_pwq_unlocked(pwq); + put_pwq_unlocked(unbound_pwq(wq, cpu)); + RCU_INIT_POINTER(*unbound_pwq_slot(wq, cpu), NULL); } - put_pwq_unlocked(wq->dfl_pwq); - wq->dfl_pwq = NULL; + put_pwq_unlocked(unbound_pwq(wq, -1)); + RCU_INIT_POINTER(*unbound_pwq_slot(wq, -1), NULL); rcu_read_unlock(); } -- 2.43.0