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Subject[PATCH] xen/mce: schedule a workqueue to avoid sleep in atomic context
Date
From aa2ce7440f16002266dc8464f749992d0c8ac0e5 Mon Sep 17 00:00:00 2001
From: Liu, Jinsong <jinsong.liu@intel.com>
Date: Tue, 12 Jun 2012 23:11:16 +0800
Subject: [PATCH] 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.

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>
---
drivers/xen/mcelog.c | 18 +++++++++++-------
1 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/drivers/xen/mcelog.c b/drivers/xen/mcelog.c
index 72e87d2..804aa3c 100644
--- a/drivers/xen/mcelog.c
+++ b/drivers/xen/mcelog.c
@@ -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;
}

--
1.7.1[unhandled content-type:application/octet-stream]
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