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Commit 1b2a0551 authored by Liu, Jinsong's avatar Liu, Jinsong Committed by Konrad Rzeszutek Wilk
Browse files

xen/mce: schedule a workqueue to avoid sleep in atomic context 



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: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Suggested-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarLiu, Jinsong <jinsong.liu@intel.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent f65c9bb3

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;

}