Since cdev mutex is after system map mutex in global lock order, free()

shall not be called while holding cdev mutex. devfs_inos unrhdr has cdev as
mutex, thus creating this LOR situation.

Postpone calling free() in kern/subr_unit.c:alloc_unr() and nested functions
until the unrhdr mutex is dropped. Save the freed items on the ppfree list
instead, and provide the clean_unrhdrl() and clean_unrhdr() functions to
clean the list.
Call clean_unrhdrl() after devfs_create() calls immediately before
dropping cdev mutex. devfs_create() is the only user of the alloc_unrl()
in the tree.

Reviewed by:	phk
Tested by:	Peter Holm
LOR:	80
Approved by:	re (kensmith)

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c
index 20d3bc3..751f524 100644
--- a/sys/kern/kern_conf.c
+++ b/sys/kern/kern_conf.c
@@ -617,6 +617,7 @@ make_dev_credv(int flags, struct cdevsw *devsw, int minornr,
 	dev->si_mode = mode;
 
 	devfs_create(dev);
+	clean_unrhdrl(devfs_inos);
 	dev_unlock();
 	return (dev);
 }
@@ -703,6 +704,7 @@ make_dev_alias(struct cdev *pdev, const char *fmt, ...)
 	va_end(ap);
 
 	devfs_create(dev);
+	clean_unrhdrl(devfs_inos);
 	dev_unlock();
 	dev_depends(pdev, dev);
 	return (dev);