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docs/devel: Mention post_load hook restrictions where we document the hook

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Accessing another device in a post_load hook is a bad idea, because
the order of device save/restore is not fixed, and so this
cross-device access makes the save/restore non-deterministic.

We previously only flagged up this requirement in the
record-and-replay developer docs; repeat it in the main migration
documentation, where a developer trying to implement a post_load hook
is more likely to see it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Peter Maydell 2024-10-03 15:34:01 +01:00 • committed by Michael Tokarev
parent db17daf8c4
commit e300f4c11d
2 changed files with 9 additions and 0 deletions
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6
docs/devel/migration/main.rst
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@ -465,6 +465,12 @@ Examples of such API functions are:
- portio_list_set_address()
- portio_list_set_enabled()
Since the order of device save/restore is not defined, you must
avoid accessing or changing any other device's state in one of these
callbacks. (For instance, don't do anything that calls ``update_irq()``
in a ``post_load`` hook.) Otherwise, restore will not be deterministic,
and this will break execution record/replay.
Iterative device migration
--------------------------