[PATCH] xen/mce: Add mutex lock and buffer to avoid sleep in atomi=
From: Liu , Jinsong
Date: Fri Jun 08 2012 - 12:56:46 EST
copy_to_user might sleep and print a stack trace if it is executed
in an atomic spinlock context. This patch add a mutex lock and a
buffer to avoid the case.
Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Liu, Jinsong <jinsong.liu@xxxxxxxxx>
---
drivers/xen/mcelog.c | 20 ++++++++++++++++----
1 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/drivers/xen/mcelog.c b/drivers/xen/mcelog.c
index 72e87d2..4046f01 100644
--- a/drivers/xen/mcelog.c
+++ b/drivers/xen/mcelog.c
@@ -56,12 +56,14 @@ static struct mcinfo_logical_cpu *g_physinfo;
static uint32_t ncpus;
=20
static DEFINE_SPINLOCK(mcelog_lock);
+static DEFINE_MUTEX(xen_mce_chrdev_read_mutex);
=20
static struct xen_mce_log xen_mcelog =3D {
.signature =3D XEN_MCE_LOG_SIGNATURE,
.len =3D XEN_MCE_LOG_LEN,
.recordlen =3D sizeof(struct xen_mce),
};
+static struct xen_mce_log xen_mcelog_u;
=20
static DEFINE_SPINLOCK(xen_mce_chrdev_state_lock);
static int xen_mce_chrdev_open_count; /* #times opened */
@@ -99,6 +101,10 @@ static int xen_mce_chrdev_release(struct inode *inode, =
struct file *file)
return 0;
}
=20
+/*
+ * copy_to_user might sleep and print a stack trace
+ * if it is executed in an atomic spinlock context
+ */
static ssize_t xen_mce_chrdev_read(struct file *filp, char __user *ubuf,
size_t usize, loff_t *off)
{
@@ -106,9 +112,15 @@ static ssize_t xen_mce_chrdev_read(struct file *filp, =
char __user *ubuf,
unsigned num;
int i, err;
=20
+ mutex_lock(&xen_mce_chrdev_read_mutex);
+
spin_lock(&mcelog_lock);
+ memcpy(&xen_mcelog_u, &xen_mcelog, sizeof(struct xen_mce_log));
=20
num =3D xen_mcelog.next;
+ memset(xen_mcelog.entry, 0, num * sizeof(struct xen_mce));
+ xen_mcelog.next =3D 0;
+ spin_unlock(&mcelog_lock);
=20
/* Only supports full reads right now */
err =3D -EINVAL;
@@ -117,20 +129,20 @@ static ssize_t xen_mce_chrdev_read(struct file *filp,=
char __user *ubuf,
=20
err =3D 0;
for (i =3D 0; i < num; i++) {
- struct xen_mce *m =3D &xen_mcelog.entry[i];
+ struct xen_mce *m =3D &xen_mcelog_u.entry[i];
=20
err |=3D copy_to_user(buf, m, sizeof(*m));
buf +=3D sizeof(*m);
}
=20
- memset(xen_mcelog.entry, 0, num * sizeof(struct xen_mce));
- xen_mcelog.next =3D 0;
+ memset(xen_mcelog_u.entry, 0, num * sizeof(struct xen_mce));
+ xen_mcelog_u.next =3D 0;
=20
if (err)
err =3D -EFAULT;
=20
out:
- spin_unlock(&mcelog_lock);
+ mutex_unlock(&xen_mce_chrdev_read_mutex);
=20
return err ? err : buf - ubuf;
}
--=20
1.7.1
--_002_DE8DF0795D48FD4CA783C40EC8292335221654SHSMSX101ccrcorpi_
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Content-Description: 0001-xen-mce-Add-mutex-lock-and-buffer-to-avoid-sleep-in-.patch
Content-Disposition: attachment;
filename="0001-xen-mce-Add-mutex-lock-and-buffer-to-avoid-sleep-in-.patch";
size=2676; creation-date="Fri, 08 Jun 2012 09:28:53 GMT";
modification-date="Fri, 08 Jun 2012 17:07:04 GMT"
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