Commit 581d21a2 authored by David Vrabel's avatar David Vrabel Committed by Juergen Gross

xenbus: fix deadlock on writes to /proc/xen/xenbus

/proc/xen/xenbus does not work correctly.  A read blocked waiting for
a xenstore message holds the mutex needed for atomic file position
updates.  This blocks any writes on the same file handle, which can
deadlock if the write is needed to unblock the read.

Clear FMODE_ATOMIC_POS when opening this device to always get
character device like sematics.
Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent 3da96be5
......@@ -538,6 +538,8 @@ static int xenbus_file_open(struct inode *inode, struct file *filp)
nonseekable_open(inode, filp);
filp->f_mode &= ~FMODE_ATOMIC_POS; /* cdev-style semantics */
u = kzalloc(sizeof(*u), GFP_KERNEL);
if (u == NULL)
return -ENOMEM;
......
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