linux-kernel - [PATCH 4.16 100/161] crypto: ccp - dont disable interrupts while setting up debugfs

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Message-Id: <20180524093030.391952472@linuxfoundation.org>
Date:   Thu, 24 May 2018 11:38:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Gary R Hook <gary.hook@....com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.16 100/161] crypto: ccp - dont disable interrupts while setting up debugfs

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

[ Upstream commit 79eb382b5e06a6dca5806465d7195d686a463ab0 ]

I don't why we need take a single write lock and disable interrupts
while setting up debugfs. This is what what happens when we try anyway:

|ccp 0000:03:00.2: enabling device (0000 -> 0002)
|BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:69
|in_atomic(): 1, irqs_disabled(): 1, pid: 3, name: kworker/0:0
|irq event stamp: 17150
|hardirqs last  enabled at (17149): [<0000000097a18c49>] restore_regs_and_return_to_kernel+0x0/0x23
|hardirqs last disabled at (17150): [<000000000773b3a9>] _raw_write_lock_irqsave+0x1b/0x50
|softirqs last  enabled at (17148): [<0000000064d56155>] __do_softirq+0x3b8/0x4c1
|softirqs last disabled at (17125): [<0000000092633c18>] irq_exit+0xb1/0xc0
|CPU: 0 PID: 3 Comm: kworker/0:0 Not tainted 4.16.0-rc2+ #30
|Workqueue: events work_for_cpu_fn
|Call Trace:
| dump_stack+0x7d/0xb6
| ___might_sleep+0x1eb/0x250
| down_write+0x17/0x60
| start_creating+0x4c/0xe0
| debugfs_create_dir+0x9/0x100
| ccp5_debugfs_setup+0x191/0x1b0
| ccp5_init+0x8a7/0x8c0
| ccp_dev_init+0xb8/0xe0
| sp_init+0x6c/0x90
| sp_pci_probe+0x26e/0x590
| local_pci_probe+0x3f/0x90
| work_for_cpu_fn+0x11/0x20
| process_one_work+0x1ff/0x650
| worker_thread+0x1d4/0x3a0
| kthread+0xfe/0x130
| ret_from_fork+0x27/0x50

If any locking is required, a simple mutex will do it.

Cc: Gary R Hook <gary.hook@....com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Acked-by: Gary R Hook <gary.hook@....com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/crypto/ccp/ccp-debugfs.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/drivers/crypto/ccp/ccp-debugfs.c
+++ b/drivers/crypto/ccp/ccp-debugfs.c
@@ -278,7 +278,7 @@ static const struct file_operations ccp_
 };
 
 static struct dentry *ccp_debugfs_dir;
-static DEFINE_RWLOCK(ccp_debugfs_lock);
+static DEFINE_MUTEX(ccp_debugfs_lock);
 
 #define	MAX_NAME_LEN	20
 
@@ -290,16 +290,15 @@ void ccp5_debugfs_setup(struct ccp_devic
 	struct dentry *debugfs_stats;
 	struct dentry *debugfs_q_instance;
 	struct dentry *debugfs_q_stats;
-	unsigned long flags;
 	int i;
 
 	if (!debugfs_initialized())
 		return;
 
-	write_lock_irqsave(&ccp_debugfs_lock, flags);
+	mutex_lock(&ccp_debugfs_lock);
 	if (!ccp_debugfs_dir)
 		ccp_debugfs_dir = debugfs_create_dir(KBUILD_MODNAME, NULL);
-	write_unlock_irqrestore(&ccp_debugfs_lock, flags);
+	mutex_unlock(&ccp_debugfs_lock);
 	if (!ccp_debugfs_dir)
 		return;