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Merge pull request #822 from sm00th/aguide 

patch-author-guide: sleeping locks in callbacks
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Joe Lawrence 2018-04-11 10:12:28 -04:00 committed by GitHub
parent ae79f2206d 808a6b83de
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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