Author: mjg
Date: Sun Jan 26 00:40:27 2020
New Revision: 357130
URL: https://svnweb.freebsd.org/changeset/base/357130
Log:
vfs: fix freevnodes count update race against preemption
vdbatch_process leaves the critical section too early, openign a time
window where another thread can get scheduled and modify vd->freevnodes.
Once it the preempted thread gets back it overrides the value with 0.
Just move critical_exit to the end of the function.
Modified:
head/sys/kern/vfs_subr.c
Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c Sun Jan 26 00:38:06 2020 (r357129)
+++ head/sys/kern/vfs_subr.c Sun Jan 26 00:40:27 2020 (r357130)
@@ -3324,10 +3324,10 @@ vdbatch_process(struct vdbatch *vd)
vp->v_dbatchcpu = NOCPU;
}
mtx_unlock(&vnode_list_mtx);
- critical_exit();
vd->freevnodes = 0;
bzero(vd->tab, sizeof(vd->tab));
vd->index = 0;
+ critical_exit();
}
static void
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