From 4bf10fa12973b82262aba78901736b1d1a13374f Mon Sep 17 00:00:00 2001 From: "Liu, Jinsong" 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. 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 [] __might_sleep+0xda/0x100 [] xen_mce_chrdev_read+0xab/0x140 [] vfs_read+0xc5/0x190 [] sys_read+0x4c/0x90 [] 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 Suggested-by: Konrad Rzeszutek Wilk Signed-off-by: Liu, Jinsong Signed-off-by: Konrad Rzeszutek Wilk --- drivers/xen/mcelog.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/drivers/xen/mcelog.c b/drivers/xen/mcelog.c index 72e87d2f1929..804aa3c181c2 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; } -- 2.39.5