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: 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> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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@ -55,7 +55,7 @@ static struct mc_info g_mi;
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static struct mcinfo_logical_cpu *g_physinfo;
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static uint32_t ncpus;
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static DEFINE_SPINLOCK(mcelog_lock);
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static DEFINE_MUTEX(mcelog_lock);
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static struct xen_mce_log xen_mcelog = {
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.signature = XEN_MCE_LOG_SIGNATURE,
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@ -106,7 +106,7 @@ static ssize_t xen_mce_chrdev_read(struct file *filp, char __user *ubuf,
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unsigned num;
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int i, err;
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spin_lock(&mcelog_lock);
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mutex_lock(&mcelog_lock);
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num = xen_mcelog.next;
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@ -130,7 +130,7 @@ static ssize_t xen_mce_chrdev_read(struct file *filp, char __user *ubuf,
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err = -EFAULT;
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out:
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spin_unlock(&mcelog_lock);
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mutex_unlock(&mcelog_lock);
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return err ? err : buf - ubuf;
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}
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@ -310,12 +310,11 @@ static int mc_queue_handle(uint32_t flags)
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}
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/* virq handler for machine check error info*/
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static irqreturn_t xen_mce_interrupt(int irq, void *dev_id)
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static void xen_mce_work_fn(struct work_struct *work)
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{
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int err;
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unsigned long tmp;
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spin_lock_irqsave(&mcelog_lock, tmp);
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mutex_lock(&mcelog_lock);
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/* urgent mc_info */
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err = mc_queue_handle(XEN_MC_URGENT);
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@ -330,8 +329,13 @@ static irqreturn_t xen_mce_interrupt(int irq, void *dev_id)
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pr_err(XEN_MCELOG
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"Failed to handle nonurgent mc_info queue.\n");
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spin_unlock_irqrestore(&mcelog_lock, tmp);
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mutex_unlock(&mcelog_lock);
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}
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static DECLARE_WORK(xen_mce_work, xen_mce_work_fn);
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static irqreturn_t xen_mce_interrupt(int irq, void *dev_id)
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{
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schedule_work(&xen_mce_work);
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return IRQ_HANDLED;
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}
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