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patch-author-guide: sleeping locks in callbacks 

Add a note about dealing with sleeping locks in callbacks.
This commit is contained in:
Artem Savkov 2018-04-06 13:27:20 +02:00
parent 055f9c8596
commit 808a6b83de
1 changed files with 4 additions and 1 deletions
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5
doc/patch-author-guide.md
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@ -193,7 +193,10 @@ static void kpatch_post_unpatch_tcp_send_challenge_ack(patch_object *obj)
+KPATCH_POST_UNPATCH_CALLBACK(kpatch_post_unpatch_tcp_send_challenge_ack);
```
Don't forget to protect access to the data as needed.
Don't forget to protect access to the data as needed. Please note that mutexes
and other sleeping locks can't be used from stop_machine context, so you will
have to check if any locks protecting the data are already held and if so
return an error from your callback function.
Also be careful when upgrading. If patch A has a pre/post-patch callback which
writes to X, and then you load patch B which is a superset of A, in some cases