If you want to be more safe, you should ask yourself: what happens if now_access_the_common_resource() crashes or loops? will the file stay locked forever? how do you detect that the other processes are starving?

You seem to have a poor understanding of how flock (and database locking) works. In addition to flock blocking until the lock succeeds (as bart explained), crashing is not a problem. When the application crashes, the filehandle will get reclaimed by the OS. The lock gets released along with the filehandle.

You're right that an application can hold the lock indefinitely. For example, the application could enter an infinite loop, or do a blocking call. Switching to a databse (especially in the manner you describe) will not magically solve these problems. Welcome to the very complex world of race conditions and fault tolerant computing.

In reply to Re^2: Ways to sequence calls from multiple processes by ikegami
in thread Ways to sequence calls from multiple processes by johnnywang

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