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Prevent interruption by the PHP "set_time_limit()" mechanism while holding the durable write lock
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Authored by epriestley on Jan 27 2021, 12:09 AM.

Details

Summary

Ref T13590. By default, PHP kills execution after web scripts run for 30 seconds. If this occurs in the locked section of a repository write while we're holding the durable write lock, the lock will get stuck.

Use "set_time_limit(0)" to prevent this mechanism from interrupting execution while the durable lock is held.

Test Plan
  • Added "set_time_limit(1)" before the lock and "while (1);" in the critical section of the lock.
  • Pushed, got the lock stuck.
  • Cleared the lock, applied this patch, pushed.
  • Got an infinite hang instead. (Normally, we expect the script to take more than 30 seconds to execute because there is a large push that executes in finite time, not because there's an infinte loop.)

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