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-rw-r--r--erts/doc/src/erl_driver.xml19
1 files changed, 13 insertions, 6 deletions
diff --git a/erts/doc/src/erl_driver.xml b/erts/doc/src/erl_driver.xml
index 2fb03954b6..8e18dd6657 100644
--- a/erts/doc/src/erl_driver.xml
+++ b/erts/doc/src/erl_driver.xml
@@ -1638,12 +1638,19 @@ ERL_DRV_EXT2TERM char *buf, ErlDrvUInt len
<fsummary>Cancel an asynchronous call</fsummary>
<desc>
<marker id="driver_async_cancel"></marker>
- <p>This function cancels an asynchronous operation, by removing
- it from the queue. Only functions in the queue can be
- cancelled; if a function is executing, it's too late to
- cancel it. The <c>async_free</c> function is also called.</p>
- <p>The return value is 1 if the operation was removed from the
- queue, otherwise 0.</p>
+ <p>This function used to cancel a scheduled asynchronous operation,
+ if it was still in the queue. It returned 1 if it succeeded, and
+ 0 if it failed.</p>
+ <p>Since it could not guarantee success, it was more or less useless.
+ The user had to implement synchronization of cancellation anyway.
+ It also unnecessarily complicated the implementation. Therefore,
+ as of OTP-R15B <c>driver_async_cancel()</c> is deprecated, and
+ scheduled for removal in OTP-R16. It will currently always fail,
+ and return 0.</p>
+ <warning><p><c>driver_async_cancel()</c> is deferred and will
+ be removed in the OTP-R16 release.</p>
+ </warning>
+
</desc>
</func>
<func>