I feel like the docs are pretty precise in what they say and why. a blocked Lock call excludes new readers from acquiring the lock.
This means, the following could happen: Goroutine 1 calls RLock, acquires a Read-Lock Goroutine 2 calls Lock, blocking Goroutine 1 calls RLock again, blocking (as no new read locks can be acquired while GR 2 is blocked). Thus, you get a deadlock. It also has a conditional on the section If a goroutine holds a RWMutex for reading and another goroutine might call > Lock […] So if you know that no other goroutine might call Lock concurrently, then yes, you can call RLock twice. I can't really imagine a setting where you'd need an RWMutex and have that assurance and need recursive read locks. But there might be one. On Mon, Sep 21, 2020 at 12:16 PM Henrik Johansson <dahankz...@gmail.com> wrote: > > https://golang.org/pkg/sync/#RWMutex > > Holds that this prohibits recursive read locks but why would it? > I understand that deadlocks can happen in case write locks are held in > between the read locks > but why can't a goroutine issue several RLock calls? > > It does actually work in the playground. > https://play.golang.org/p/nOehJaeikxA > Is this simply a recommendation or should the docs be updated to clarify > what this means? > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/CAKOF696YKSGn3j%2BcyX7o0ukA7wnD2Kq19_QGefUoeMELUZGOWA%40mail.gmail.com > <https://groups.google.com/d/msgid/golang-nuts/CAKOF696YKSGn3j%2BcyX7o0ukA7wnD2Kq19_QGefUoeMELUZGOWA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAEkBMfHGbQyvmcrxbGYLN6BZqAQN3K1i_HxtQTXmV22668WWQg%40mail.gmail.com.
