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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B23AC001E0 for ; Sat, 21 Oct 2023 07:25:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229715AbjJUHZS (ORCPT ); Sat, 21 Oct 2023 03:25:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35508 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229472AbjJUHZQ (ORCPT ); Sat, 21 Oct 2023 03:25:16 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51B56D65 for ; Sat, 21 Oct 2023 00:25:13 -0700 (PDT) Received: from dggpeml500002.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4SCCYJ6GSYzNmNP; Sat, 21 Oct 2023 15:21:08 +0800 (CST) Received: from [10.67.120.218] (10.67.120.218) by dggpeml500002.china.huawei.com (7.185.36.158) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Sat, 21 Oct 2023 15:25:09 +0800 Subject: Re: [PATCH 1/3] coresight: ultrasoc-smb: fix sleep while close preempt in enable_smb To: Jonathan Cameron , References: <20231012094706.21565-1-hejunhao3@huawei.com> <20231012094706.21565-2-hejunhao3@huawei.com> <20231019142956.00005a3b@huawei.com> CC: , , , , , , From: hejunhao Message-ID: <2f6c2af0-b867-5be5-ed37-c5d71b1ed1ce@huawei.com> Date: Sat, 21 Oct 2023 15:25:09 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20231019142956.00005a3b@huawei.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.120.218] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpeml500002.china.huawei.com (7.185.36.158) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jonathan, On 2023/10/19 21:30, Jonathan Cameron wrote: > On Thu, 12 Oct 2023 17:47:04 +0800 > Junhao He wrote: > >> When we to enable the SMB by perf, the perf sched will call perf_ctx_lock() >> to close system preempt in event_function_call(). But SMB::enable_smb() use >> mutex to lock the critical section, which may sleep. >> >> BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580 >> in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 153023, name: perf >> preempt_count: 2, expected: 0 >> RCU nest depth: 0, expected: 0 >> INFO: lockdep is turned off. >> irq event stamp: 0 >> hardirqs last enabled at (0): [<0000000000000000>] 0x0 >> hardirqs last disabled at (0): [] copy_process+0xae8/0x2b48 >> softirqs last enabled at (0): [] copy_process+0xae8/0x2b48 >> softirqs last disabled at (0): [<0000000000000000>] 0x0 >> CPU: 2 PID: 153023 Comm: perf Kdump: loaded Tainted: G W O 6.5.0-rc4+ #1 >> >> Call trace: >> ... >> __mutex_lock+0xbc/0xa70 >> mutex_lock_nested+0x34/0x48 >> smb_update_buffer+0x58/0x360 [ultrasoc_smb] >> etm_event_stop+0x204/0x2d8 [coresight] >> etm_event_del+0x1c/0x30 [coresight] >> event_sched_out+0x17c/0x3b8 >> group_sched_out.part.0+0x5c/0x208 >> __perf_event_disable+0x15c/0x210 >> event_function+0xe0/0x230 >> remote_function+0xb4/0xe8 >> generic_exec_single+0x160/0x268 >> smp_call_function_single+0x20c/0x2a0 >> event_function_call+0x20c/0x220 >> _perf_event_disable+0x5c/0x90 >> perf_event_for_each_child+0x58/0xc0 >> _perf_ioctl+0x34c/0x1250 >> perf_ioctl+0x64/0x98 >> ... >> >> Use spinlock replace mutex to control driver data access to one at a >> time. But the function copy_to_user() may sleep so spinlock do not to >> lock it. > I'd like to see a comment on why we no longer need to lock over the copy_to_user > rather than simply that we can't. Yes, I will do that. >> Fixes: 06f5c2926aaa ("drivers/coresight: Add UltraSoc System Memory Buffer driver") >> Signed-off-by: Junhao He > A follow up patch could change a lot of this to use the new cleanup.h (don't want that > in the fix though as will make back porting trickier.). > That should let you do > guard(spin_lock)(&drvdata->spinlock); > and then use direct returns instead of goto complexity. > > > > Jonathan Thanks for sharing. I will append up a new patch to use guards to reduce gotos. > >> @@ -132,10 +132,8 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len, >> if (!len) >> return 0; >> >> - mutex_lock(&drvdata->mutex); >> - >> if (!sdb->data_size) >> - goto out; >> + return 0; >> >> to_copy = min(sdb->data_size, len); >> >> @@ -145,20 +143,18 @@ static ssize_t smb_read(struct file *file, char __user *data, size_t len, >> >> if (copy_to_user(data, sdb->buf_base + sdb->buf_rdptr, to_copy)) { >> dev_dbg(dev, "Failed to copy data to user\n"); >> - to_copy = -EFAULT; >> - goto out; >> + return -EFAULT; >> } >> >> + spin_lock(&drvdata->spinlock); >> *ppos += to_copy; >> - > Unrelated white space change that shouldn't be here. Ok, i will drop this white space Thanks for the comments! Best regards, Junhao. > >> smb_update_read_ptr(drvdata, to_copy); >> >> - dev_dbg(dev, "%zu bytes copied\n", to_copy); >> -out: >> if (!sdb->data_size) >> smb_reset_buffer(drvdata); >> - mutex_unlock(&drvdata->mutex); >> + spin_unlock(&drvdata->spinlock); >> >> + dev_dbg(dev, "%zu bytes copied\n", to_copy); >> return to_copy; >> } > > . >