|From:||Chapman Flack <chap(at)anastigmatix(dot)net>|
|To:||PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>|
|Subject:||Signals in a BGW|
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I'm curious about handling signals in a background worker.
As I understand it, these are blocked when the BGW is born, until
enabled with BackgroundWorkerUnblockSignals() after possible
Is there a known, default behavior that some signals will
have, if I simply BackgroundWorkerUnblockSignals() without customizing?
Will SIGINT and SIGTERM, for example, have default handlers that
interact with the volatile flags in miscadmin.h that are used by
CHECK_FOR_INTERRUPTS, and set the process latch?
I notice that the worker_spi example code customizes SIGHUP
and SIGTERM, giving them handlers that set a (different, local
to the module) volatile flag, and set the process latch.
The example code does call CHECK_FOR_INTERRUPTS, though I assume
this won't detect ProcDie at all, now that the custom SIGTERM
handler is setting a different, local flag. Perhaps it still
does something useful with QueryCancel?
Does this use of a custom SIGTERM handler, setting a custom flag,
setting the process latch, and then checked in custom code,
accomplish something important that would not be accomplished
by a generic handler and CHECK_FOR_INTERRUPTS ?
I'm just not clearly grasping the reason it's customized here.
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