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authorRickard Green <[email protected]>2016-08-02 15:58:06 +0200
committerRickard Green <[email protected]>2016-08-29 16:26:24 +0200
commit9d0638216d35ca0f21c1eea20f8daa3992ac4f71 (patch)
treeb270d8f0226e88c376826584c4ea88ae377dff6f /erts/doc
parent2fe03e832adb11c50bcfc62679cf17779b284124 (diff)
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Fix purge of code
Ensure that we cannot get any dangling pointers into code that has been purged. This is done by a two phase purge. At first phase all fun entries pointing into the code to purge are marked for purge. All processes trying to call these funs will be suspended and by this we avoid getting new direct references into the code. When all processes has been checked, these processes are resumed. The new purge strategy now also completely ignore the existence of indirect references to the code (funs). If such exist, they will cause bad fun exceptions to the caller, but will not prevent a soft purge or cause a kill of a process having such live references during a hard purge. This since it is impossible to give any guarantees that no processes in the system have such indirect references. Even when the system is completely clean from such references, new ones can appear via distribution and/or disk.
Diffstat (limited to 'erts/doc')
-rw-r--r--erts/doc/src/erlang.xml23
1 files changed, 23 insertions, 0 deletions
diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 6289f033b2..a146d4f2b1 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -764,6 +764,29 @@
and the operation was requested
by passing option <c>{allow_gc, false}</c>.</p></item>
</taglist>
+ <note>
+ <p>
+ Up until ERTS version 8.*, the check process code operation
+ checks for all types of references to the old code. That is,
+ direct references (e.g. return addresses on the process
+ stack), indirect references (<c>fun</c>s in process
+ context), and references to literals in the code.
+ </p>
+ <p>
+ As of ERTS version 9.0, the check process code operation
+ only checks for direct references to the code. Indirect
+ references via <c>fun</c>s will be ignored. If such
+ <c>fun</c>s exist and are used after a purge of the old
+ code, an exception will be raised upon usage (same as
+ the case when the <c>fun</c> is received by the process
+ after the purge). Literals will be taken care of (copied)
+ at a later stage. This behavior can as of ERTS version
+ 8.1 be enabled when
+ <seealso marker="doc/installation_guide:INSTALL#Advanced-configuration-and-build-of-ErlangOTP_Configuring">building OTP</seealso>,
+ and will automatically be enabled if dirty scheduler
+ support is enabled.
+ </p>
+ </note>
<p>See also <seealso marker="kernel:code">code(3)</seealso>.</p>
<p>Failures:</p>
<taglist>