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prevent deadlock in List() for B2 when b2.connections=1

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This is a fix for the following situation (gh-1188):

List() grabs a semaphore token upon entry, starts a goroutine, and
does not release the token until the routine exits (via a defer).

The goroutine iterates over the results from ListCurrentObjects(),
sending them one at a time to a channel, where they are ultimately
processed by be.Load().

Since be.Load() also needs a token, this will result in deadlock if
b2.connections=1.

This fix changes List() so that the token is only held during the call
to ListCurrentObjects().
This commit is contained in:
George Armhold 2017-10-28 18:39:56 -04:00
parent 53a554c89d
commit 3304b0fcf0
1 changed files with 2 additions and 3 deletions
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5
internal/backend/b2/b2.go
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@ -307,18 +307,17 @@ func (be *b2Backend) List(ctx context.Context, t restic.FileType) <-chan string
ctx, cancel := context.WithCancel(ctx) ctx, cancel := context.WithCancel(ctx)
be.sem.GetToken()
go func() { go func() {
defer close(ch) defer close(ch)
defer cancel() defer cancel()
defer be.sem.ReleaseToken()
prefix := be.Dirname(restic.Handle{Type: t}) prefix := be.Dirname(restic.Handle{Type: t})
cur := &b2.Cursor{Prefix: prefix} cur := &b2.Cursor{Prefix: prefix}
for { for {
be.sem.GetToken()
objs, c, err := be.bucket.ListCurrentObjects(ctx, be.listMaxItems, cur) objs, c, err := be.bucket.ListCurrentObjects(ctx, be.listMaxItems, cur)
be.sem.ReleaseToken()
if err != nil && err != io.EOF { if err != nil && err != io.EOF {
return return
} }