[Xen-devel] [PATCH] xen/mce: schedule a workqueue to avoid sleep in atomic context

["Liu, Jinsong" <jinsong.liu@xxxxxxxxx>]

>From aa2ce7440f16002266dc8464f749992d0c8ac0e5 Mon Sep 17 00:00:00 2001
From: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
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@xxxxxxxxxx>
Suggested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
---
 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

Attachment: 0001-xen-mce-schedule-a-workqueue-to-avoid-sleep-in-atomi.patch
Description: 0001-xen-mce-schedule-a-workqueue-to-avoid-sleep-in-atomi.patch

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel