xen/mce: schedule a workqueue to avoid sleep in atomic context (1b2a0551) · Commits · 戴 / test

copy_to_user might sleep and print a stack trace if it is executed in an atomic spinlock context. Like this: (XEN) CMCI: send CMCI to DOM0 through virq BUG: sleeping function called from invalid context at /home/konradinux/kernel.h:199 in_atomic(): 1, irqs_disabled(): 0, pid: 4581, name: mcelog Pid: 4581, comm: mcelog Tainted: G O 3.5.0-rc1upstream-00003-g149000b-dirty #1 [<ffffffff8109ad9a>] __might_sleep+0xda/0x100 [<ffffffff81329b0b>] xen_mce_chrdev_read+0xab/0x140 [<ffffffff81148945>] vfs_read+0xc5/0x190 [<ffffffff81148b0c>] sys_read+0x4c/0x90 [<ffffffff815bd039>] system_call_fastpath+0x16 This patch schedule a workqueue for IRQ handler to poll the data, and use mutex instead of spinlock, so copy_to_user sleep in atomic context would not occur. Reported-by:

Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Suggested-by:

Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by:

Liu, Jinsong <jinsong.liu@intel.com> Signed-off-by:

Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/mcelog.c

+11 −7

Original line number	Diff line number	Diff line
		@@ -55,7 +55,7 @@ static struct mc_info g_mi;
		static struct mcinfo_logical_cpu *g_physinfo;
		static uint32_t ncpus;

		static DEFINE_SPINLOCK(mcelog_lock);
		static DEFINE_MUTEX(mcelog_lock);

		static struct xen_mce_log xen_mcelog = {
		.signature = XEN_MCE_LOG_SIGNATURE,
		@@ -106,7 +106,7 @@ static ssize_t xen_mce_chrdev_read(struct file filp, char __user ubuf,
		unsigned num;
		int i, err;

		spin_lock(&mcelog_lock);
		mutex_lock(&mcelog_lock);

		num = xen_mcelog.next;

		@@ -130,7 +130,7 @@ static ssize_t xen_mce_chrdev_read(struct file filp, char __user ubuf,
		err = -EFAULT;

		out:
		spin_unlock(&mcelog_lock);
		mutex_unlock(&mcelog_lock);

		return err ? err : buf - ubuf;
		}
		@@ -310,12 +310,11 @@ static int mc_queue_handle(uint32_t flags)
		}

		/* virq handler for machine check error info*/
		static irqreturn_t xen_mce_interrupt(int irq, void *dev_id)
		static void xen_mce_work_fn(struct work_struct *work)
		{
		int err;
		unsigned long tmp;

		spin_lock_irqsave(&mcelog_lock, tmp);
		mutex_lock(&mcelog_lock);

		/* urgent mc_info */
		err = mc_queue_handle(XEN_MC_URGENT);
		@@ -330,8 +329,13 @@ static irqreturn_t xen_mce_interrupt(int irq, void *dev_id)
		pr_err(XEN_MCELOG
		"Failed to handle nonurgent mc_info queue.\n");

		spin_unlock_irqrestore(&mcelog_lock, tmp);
		mutex_unlock(&mcelog_lock);
		}
		static DECLARE_WORK(xen_mce_work, xen_mce_work_fn);

		static irqreturn_t xen_mce_interrupt(int irq, void *dev_id)
		{
		schedule_work(&xen_mce_work);
		return IRQ_HANDLED;
		}

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