method

start_exclusive

v7.1.3.4 - Show latest stable - 0 notes - Class: ShareLock

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start_exclusive(purpose: nil, compatible: [], no_wait: false) public

Returns false if no_wait is set and the lock is not immediately available. Otherwise, returns true after the lock has been acquired.

purpose and compatible work together; while this thread is waiting for the exclusive lock, it will yield its share (if any) to any other attempt whose purpose appears in this attempt’s compatible list. This allows a “loose” upgrade, which, being less strict, prevents some classes of deadlocks.

For many resources, loose upgrades are sufficient: if a thread is awaiting a lock, it is not running any other code. With purpose matching, it is possible to yield only to other threads whose activity will not interfere.

Show source

# File activesupport/lib/active_support/concurrency/share_lock.rb, line 76
      def start_exclusive(purpose: nil, compatible: [], no_wait: false)
        synchronize do
          unless @exclusive_thread == Thread.current
            if busy_for_exclusive?(purpose)
              return false if no_wait

              yield_shares(purpose: purpose, compatible: compatible, block_share: true) do
                wait_for(:start_exclusive) { busy_for_exclusive?(purpose) }
              end
            end
            @exclusive_thread = Thread.current
          end
          @exclusive_depth += 1

          true
        end
      end

start_exclusive

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