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 2A98014E2F9; Wed, 3 Apr 2024 17:56:17 +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=1712166977; cv=none; b=Tm/fSWCgLUOfnq1wHC1CxYH2PWnXTsePrWW41fSQLe2daVBP/1UG26mRpGCxAqjQeA85dp5tSRiZj7+2+pY5YD1XdVP736uGQeUwH37DdE+a/SjLj8AYECPW8WN9tQYHisssXeAryGslvkOFGmZuqKsc4ok9L6XFGcxa0sWvwK8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712166977; c=relaxed/simple; bh=lNsnqzLs6qM6H3tLQYPevG1PijCLapvkul3YZLadaI8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Dm5LpVoAlLeSRBf+hx/jQ5d4owpqlCm3YzVlUSEn0SKPgE5VKBOiUDGHvWE4z7VrfVnUitlSIsw6Pt8essh+t4tQxPgn4E+FUCt5p4ddNSsLOX14WjFY6Q5qS4lhZasHGpUddXz2cLVaV1lHOCp+hu6zciuwWXaXDQ4O16/DITU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=coij3cRv; 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="coij3cRv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99C9EC433F1; Wed, 3 Apr 2024 17:56:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1712166977; bh=lNsnqzLs6qM6H3tLQYPevG1PijCLapvkul3YZLadaI8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=coij3cRv1weq4d1Keoft2hddoNtXNwwUAl3K7teQLwSaOn8IM1gAOsWsY/F61uTKl a+YeeGj3/07Tw9QraL7Fqt1h6sAOYjGlc7yT8DKiviqZxGUnBExAdmVMGS14f4y08f IXdk3J5Ib+iyXNoW5tLfWR7kmKLYyHYpCse8uJXA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Thorsten Leemhuis , Tejun Heo , Marek Szyprowski , Nathan Chancellor , Sasha Levin , Audra Mitchell Subject: [PATCH 6.8 05/11] Revert "workqueue: RCU protect wq->dfl_pwq and implement accessors for it" Date: Wed, 3 Apr 2024 19:55:44 +0200 Message-ID: <20240403175125.945264939@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240403175125.754099419@linuxfoundation.org> References: <20240403175125.754099419@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Greg Kroah-Hartman This reverts commit 3fb5dbc8bb3759ad0a82d6bf5ed32866c0410a79 which is commit 9f66cff212bb3c1cd25996aaa0dfd0c9e9d8baab upstream. The workqueue patches backported to 6.8.y caused some reported regressions, so revert them for now. Reported-by: Thorsten Leemhuis Cc: Tejun Heo Cc: Marek Szyprowski Cc: Nathan Chancellor Cc: Sasha Levin Cc: Audra Mitchell Link: https://lore.kernel.org/all/ce4c2f67-c298-48a0-87a3-f933d646c73b@leemhuis.info/ Signed-off-by: Greg Kroah-Hartman --- kernel/workqueue.c | 64 +++++++++++++++++++---------------------------------- 1 file changed, 24 insertions(+), 40 deletions(-) --- 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 __rcu *dfl_pwq; /* PW: only for unbound wqs */ + struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */ #ifdef CONFIG_SYSFS struct wq_device *wq_dev; /* I: for sysfs interface */ @@ -635,23 +635,6 @@ static int worker_pool_assign_id(struct 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; @@ -4341,11 +4324,10 @@ static void wq_calc_pod_cpumask(struct w "possible intersect\n"); } -/* install @pwq into @wq and return the old pwq, @cpu < 0 for dfl_pwq */ +/* install @pwq into @wq's cpu_pwq and return the old 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); @@ -4354,8 +4336,8 @@ static struct pool_workqueue *install_un /* link_pwq() can handle duplicate calls */ link_pwq(pwq); - old_pwq = rcu_access_pointer(*slot); - rcu_assign_pointer(*slot, pwq); + old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu)); + rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq); return old_pwq; } @@ -4455,11 +4437,14 @@ static void apply_wqattrs_commit(struct copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs); - /* save the previous pwqs and install the new ones */ + /* save the previous pwq and install the new one */ for_each_possible_cpu(cpu) ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu, ctx->pwq_tbl[cpu]); - ctx->dfl_pwq = install_unbound_pwq(ctx->wq, -1, ctx->dfl_pwq); + + /* @dfl_pwq might not have been used, ensure it's linked */ + link_pwq(ctx->dfl_pwq); + swap(ctx->wq->dfl_pwq, ctx->dfl_pwq); mutex_unlock(&ctx->wq->mutex); } @@ -4569,7 +4554,9 @@ static void wq_update_pod(struct workque /* nothing to do if the target cpumask matches the current pwq */ wq_calc_pod_cpumask(target_attrs, cpu, off_cpu); - if (wqattrs_equal(target_attrs, unbound_pwq(wq, cpu)->pool->attrs)) + 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)) return; /* create a new pwq */ @@ -4587,11 +4574,10 @@ static void wq_update_pod(struct workque use_dfl_pwq: mutex_lock(&wq->mutex); - 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); + 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); out_unlock: mutex_unlock(&wq->mutex); put_pwq_unlocked(old_pwq); @@ -4629,13 +4615,10 @@ static int alloc_and_link_pwqs(struct wo 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 */ - dfl_pwq = rcu_access_pointer(wq->dfl_pwq); - WARN(!ret && (wq->pwqs.next != &dfl_pwq->pwqs_node || - wq->pwqs.prev != &dfl_pwq->pwqs_node), + WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node || + wq->pwqs.prev != &wq->dfl_pwq->pwqs_node), "ordering guarantee broken for workqueue %s\n", wq->name); } else { ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]); @@ -4866,7 +4849,7 @@ static bool pwq_busy(struct pool_workque if (pwq->nr_in_flight[i]) return true; - if ((pwq != rcu_access_pointer(pwq->wq->dfl_pwq)) && (pwq->refcnt > 1)) + if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1)) return true; if (!pwq_is_empty(pwq)) return true; @@ -4950,12 +4933,13 @@ void destroy_workqueue(struct workqueue_ rcu_read_lock(); for_each_possible_cpu(cpu) { - put_pwq_unlocked(unbound_pwq(wq, cpu)); - RCU_INIT_POINTER(*unbound_pwq_slot(wq, cpu), NULL); + 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, -1)); - RCU_INIT_POINTER(*unbound_pwq_slot(wq, -1), NULL); + put_pwq_unlocked(wq->dfl_pwq); + wq->dfl_pwq = NULL; rcu_read_unlock(); }