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-rw-r--r--erts/doc/src/driver_entry.xml23
1 files changed, 23 insertions, 0 deletions
diff --git a/erts/doc/src/driver_entry.xml b/erts/doc/src/driver_entry.xml
index a2efdf3ebc..929c485c36 100644
--- a/erts/doc/src/driver_entry.xml
+++ b/erts/doc/src/driver_entry.xml
@@ -34,6 +34,29 @@
<lib>driver_entry</lib>
<libsummary>The driver-entry structure used by erlang drivers.</libsummary>
<description>
+ <marker id="WARNING"/>
+ <warning><p><em>Use this functionality with extreme care!</em></p>
+ <p>A driver callback is executed as a direct extension of the
+ native code of the VM. Execution is not made in a safe environment.
+ The VM can <em>not</em> provide the same services as provided when
+ executing Erlang code, such as preemptive scheduling or memory
+ protection. If the driver callback function doesn't behave well,
+ the whole VM will misbehave.</p>
+ <list>
+ <item><p>A driver callback that crash will crash the whole VM.</p></item>
+ <item><p>An erroneously implemented driver callback might cause
+ a VM internal state inconsistency which may cause a crash of the VM,
+ or miscellaneous misbehaviors of the VM at any point after the call
+ to the driver callback.</p></item>
+ <item><p>A driver callback that do
+ <seealso marker="erl_driver#lengthy_work">lengthy work</seealso>
+ before returning will degrade responsiveness of the VM,
+ and may cause miscellaneous strange behaviors. Such strange behaviors
+ include, but are not limited to, extreme memory usage, and bad load
+ balancing between schedulers. Strange behaviors that might occur due
+ to lengthy work may also vary between OTP releases.</p></item>
+ </list>
+ </warning>
<p>
As of erts version 5.9 (OTP release R15B) the driver interface
has been changed with larger types for the callbacks