From 5feb7dede93900b0012e3047985d9a1739f3ed5d Mon Sep 17 00:00:00 2001 From: Simon Ser Date: Sat, 4 May 2019 14:13:57 +0000 Subject: lib/ui: fix Grid race condition This was is more complicated than others. The cells list is accessed by multiple goroutines: - Some change the Grid's contents via AddChild/RemoveChild - Some call Draw - Some invalidate the grid via Invalidate Invalidate calls are tricky to handle because they will also invalidate all child cells. This will inturn trigger the cellInvalidated callback, which needs to read the list of cells. For this reason, we use a sync.RWLock which allows multiple concurrent reads. Below is the race fixed by this commit. Read at 0x00c0000bc3d0 by goroutine 7: git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Grid).cellInvalidated() /home/simon/src/aerc2/lib/ui/grid.go:181 +0x45 git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Grid).cellInvalidated-fm() /home/simon/src/aerc2/lib/ui/grid.go:179 +0x55 git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate() /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85 git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Bordered).contentInvalidated-fm() /home/simon/src/aerc2/lib/ui/borders.go:39 +0x56 git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate() /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85 git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList.func1() /home/simon/src/aerc2/widgets/dirlist.go:81 +0x55 git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate() /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85 git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start.func1() /home/simon/src/aerc2/widgets/spinner.go:88 +0x82 Previous write at 0x00c0000bc3d0 by main goroutine: [failed to restore the stack] Goroutine 7 (running) created at: git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start() /home/simon/src/aerc2/widgets/spinner.go:46 +0x98 git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList() /home/simon/src/aerc2/widgets/dirlist.go:37 +0x28b git.sr.ht/~sircmpwn/aerc2/widgets.NewAccountView() /home/simon/src/aerc2/widgets/account.go:49 +0x5ca git.sr.ht/~sircmpwn/aerc2/widgets.NewAerc() /home/simon/src/aerc2/widgets/aerc.go:60 +0x807 main.main() /home/simon/src/aerc2/aerc.go:65 +0x33e --- lib/ui/grid.go | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/ui/grid.go b/lib/ui/grid.go index 3fc7f04..f36a16a 100644 --- a/lib/ui/grid.go +++ b/lib/ui/grid.go @@ -3,6 +3,7 @@ package ui import ( "fmt" "math" + "sync" "sync/atomic" ) @@ -12,8 +13,11 @@ type Grid struct { rowLayout []gridLayout columns []GridSpec columnLayout []gridLayout - cells []*GridCell invalid bool + + // Protected by mutex + cells []*GridCell + mutex sync.RWMutex } const ( @@ -73,6 +77,9 @@ func (grid *Grid) Columns(spec []GridSpec) *Grid { } func (grid *Grid) Children() []Drawable { + grid.mutex.RLock() + defer grid.mutex.RUnlock() + children := make([]Drawable, len(grid.cells)) for i, cell := range grid.cells { children[i] = cell.Content @@ -85,6 +92,10 @@ func (grid *Grid) Draw(ctx *Context) { if invalid { grid.reflow(ctx) } + + grid.mutex.RLock() + defer grid.mutex.RUnlock() + for _, cell := range grid.cells { cellInvalid := cell.invalid.Load().(bool) if !cellInvalid && !invalid { @@ -148,9 +159,11 @@ func (grid *Grid) invalidateLayout() { func (grid *Grid) Invalidate() { grid.invalidateLayout() + grid.mutex.RLock() for _, cell := range grid.cells { cell.Content.Invalidate() } + grid.mutex.RUnlock() } func (grid *Grid) AddChild(content Drawable) *GridCell { @@ -159,7 +172,9 @@ func (grid *Grid) AddChild(content Drawable) *GridCell { ColSpan: 1, Content: content, } + grid.mutex.Lock() grid.cells = append(grid.cells, cell) + grid.mutex.Unlock() cell.Content.OnInvalidate(grid.cellInvalidated) cell.invalid.Store(true) grid.invalidateLayout() @@ -167,23 +182,27 @@ func (grid *Grid) AddChild(content Drawable) *GridCell { } func (grid *Grid) RemoveChild(cell *GridCell) { + grid.mutex.Lock() for i, _cell := range grid.cells { if _cell == cell { grid.cells = append(grid.cells[:i], grid.cells[i+1:]...) break } } + grid.mutex.Unlock() grid.invalidateLayout() } func (grid *Grid) cellInvalidated(drawable Drawable) { var cell *GridCell + grid.mutex.RLock() for _, cell = range grid.cells { if cell.Content == drawable { break } cell = nil } + grid.mutex.RUnlock() if cell == nil { panic(fmt.Errorf("Attempted to invalidate unknown cell")) } -- cgit v1.2.3