CVS commit: src/sys

[YAMAMOTO Takashi <yamt%netbsd.org@localhost>]

Module Name:    src
Committed By:   yamt
Date:           Sat May 16 08:29:54 UTC 2009

Modified Files:
        src/sys/kern: vfs_subr.c
        src/sys/sys: vnode.h

Log Message:
put a flag bit into v_usecount to prevent vtryget during getcleanvnode.
this fixes the following deadlock.

        a thread doing getcleanvnode:
        pick a vnode
        acqure v_interlock
        v_usecount++
        call vclean

                now, another thread doing cache_lookup:
                picks the vnode
                vtryget succeed
                vn_lock succeed

        now in vclean:
        set VI_XLOCK (too late to be noticed by the competing thread)
        wait on the vnode lock (this might violate locking order)

the use of a flag bit was suggested by Andrew Doran.  PR/41374.


To generate a diff of this commit:
cvs rdiff -u -r1.378 -r1.379 src/sys/kern/vfs_subr.c
cvs rdiff -u -r1.206 -r1.207 src/sys/sys/vnode.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.