Reader/Writer Lock Illustrated

Ar

Multiple readers may hold

the lock concurrently in shared mode.

Writers always hold the lock in exclusive mode, and must wait for all readers or writer to exit.

mode read write max allowed

shared yes no many

exclusive yes yes one

not holder no no many

Ar

Rr

Rr

Rw

Aw

If each thread acquires the lock in exclusive (*write) mode, SharedLock functions exactly as an ordinary mutex.

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