Panic/return false on overflow in no_threads read/try_read impl#154526
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asder8215 wants to merge 2 commits intorust-lang:mainfrom
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Panic/return false on overflow in no_threads read/try_read impl#154526asder8215 wants to merge 2 commits intorust-lang:mainfrom
asder8215 wants to merge 2 commits intorust-lang:mainfrom
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| assert!(m == isize::MAX, "too many active read locks on RwLock"); | ||
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| if m >= 0 { | ||
| self.mode.set(m + 1); |
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Let's write this as m.checked_add(1).expect("rwlock overflowed read locks"), and same with below.
I would also move the subtraction in the unlock code to do the same. It's not as necessary, but I think it would be good to confirm we are in fact holding a read lock and should be cheap for this implementation.
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As per discussion with Mark in #153555, it's possible for
no_threadsimpl ofRwLockto trigger a silent overflow onRwLock::read/RwLock::try_readif we try to acquire more thanisize::MAXread locks. This PR adds an explicit panic/return false when our read lock counter is atisize::MAXforRwLock::read/RwLock::try_read; the message is similar to that of sys/sync/rwlock/futex.rs here.