diff options
| author | Fabricio Voznika <fvoznika@google.com> | 2021-07-12 18:27:59 -0700 |
|---|---|---|
| committer | gVisor bot <gvisor-bot@google.com> | 2021-07-12 18:30:46 -0700 |
| commit | 520795aaad701854e9ffe84de1108954cf2b77f8 (patch) | |
| tree | 9f2aa17263053f5fd3edd7614679341202129c08 /pkg/refsvfs2 | |
| parent | 275932bf0852431b6f307ba9c45f26073d20ac62 (diff) | |
Fix deadlock in procfs
Kernfs provides an internal mechanism to defer calls to `DecRef()` because
on the last reference `Filesystem.mu` must be held and most places that
need to call `DecRef()` are inside the lock. The same can be true for
filesystems that extend kernfs. procfs needs to look up files and `DecRef()`
them inside the `kernfs.Filesystem.mu`. If the files happen to be procfs
files, it can deadlock trying to decrement if it's the last reference.
This change extends the mechanism to external callers to defer DecRefs
to `vfs.FileDescription` and `vfs.VirtualDentries`.
PiperOrigin-RevId: 384361647
Diffstat (limited to 'pkg/refsvfs2')
| -rw-r--r-- | pkg/refsvfs2/refs.go | 5 | ||||
| -rw-r--r-- | pkg/refsvfs2/refs_template.go | 2 |
2 files changed, 6 insertions, 1 deletions
diff --git a/pkg/refsvfs2/refs.go b/pkg/refsvfs2/refs.go index ef8beb659..fe3e4a1ca 100644 --- a/pkg/refsvfs2/refs.go +++ b/pkg/refsvfs2/refs.go @@ -28,6 +28,11 @@ type RefCounter interface { // DecRef decrements the object's reference count. Users of refs_template.Refs // may specify a destructor to be called once the reference count reaches zero. DecRef(ctx context.Context) +} + +// TryRefCounter is like RefCounter but allow the ref increment to be tried. +type TryRefCounter interface { + RefCounter // TryIncRef attempts to increment the reference count, but may fail if all // references have already been dropped, in which case it returns false. If diff --git a/pkg/refsvfs2/refs_template.go b/pkg/refsvfs2/refs_template.go index 1102c8adc..55b0a60a1 100644 --- a/pkg/refsvfs2/refs_template.go +++ b/pkg/refsvfs2/refs_template.go @@ -101,7 +101,7 @@ func (r *Refs) IncRef() { } } -// TryIncRef implements refs.RefCounter.TryIncRef. +// TryIncRef implements refs.TryRefCounter.TryIncRef. // // To do this safely without a loop, a speculative reference is first acquired // on the object. This allows multiple concurrent TryIncRef calls to distinguish |