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When a module has been purged from memory, any literals belonging
to that module will be copied to all processes that hold references
to them.
The max heap size limit would be ignored in the garbage collection
initiated when copying literals to a process. If the max heap size
was exceeded, the process would typically be terminated in the
following garbage collection.
Since the process would be killed anyway later, kill the process
before copying a literal that would make it exceed its max heap
size.
While at it, also fix a potential bug in `erlang:garbage_collect/0`.
If it was found that the max heap sized had been exceeded while
executing `erlang:garbage_collect/0`, the process would enter a
kind of zombie state instead of being properly terminated.
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See also ERL-553 and ERL-544 (commit c3ddb0f).
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When compiling Erlang source code, the literal area for the
module can only contain data types that have a literal
syntax.
However, it is possible to sneak in other data types
(such as references) in the literal pool by compiling from
abstract or assembly code. Those "fake literals" would work
fine, but would crash the runtime system when the module containing
the literals was purged.
Although fake literals are not officially supported, the
runtime should not crash when attempting to use them.
Therefore, fix the garbage collection of literals and releasing
of literal areas.
https://bugs.erlang.org/browse/ERL-508
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* rickard/purge-hibernated-19:
Update testcase to check that purge handle hibernated process correct
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* rickard/purge-hibernated:
Update testcase to check that purge handle hibernated process correct
Conflicts:
erts/emulator/test/code_SUITE.erl
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The new chunk stores atoms encoded in UTF-8.
beam_lib has also been modified to handle the new
'utf8_atoms' attribute while the 'atoms' attribute
may be a missing chunk from now on.
The binary_to_atom/2 BIF can now encode any utf8
binary with up to 255 characters.
The list_to_atom/1 BIF can now accept codepoints
higher than 255 with up to 255 characters (thanks
to Björn Gustavsson).
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Monitor first, then ask to terminate.
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Hard to unit test now when it takes a magic HipeLoaderState
as argument. All hipe testing should be enough exercise for
code:make_stub_module.
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A step toward better integration of hipe load and purge
Highlights:
* code_server no longer needs to call hipe_unified_loader:post_beam_load/1
Instead new internal function hipe_redirect_to_module()
is called by loading BIFs to patch native call sites if needed.
* hipe_purge_module() is called by erts_internal:purge_module/2
to purge any native code.
* struct hipe_mfa_info redesigned and only used for exported
functions that are called from or implemented by native code.
A list of native call sites (struct hipe_ref) are kept for each hipe_mfa_info.
* struct hipe_sdesc used by hipe_find_mfa_from_ra()
to build native stack traces.
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The code purger process handles vast amounts of messages when
there are lots of processes alive. A single message in the
message queue that does not match will in such cases cause
lots of extra work. The code purger process now always picks
the first message in the message queue, and by this avoid
this extra work.
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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.
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Specifically t_copy_literals_frags/1 tries to test literals
in message heap fragments.
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Those clause are obsolete and never used by common_test.
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As a first step to removing the test_server application as
as its own separate application, change the inclusion of
test_server.hrl to an inclusion of ct.hrl and remove the
inclusion of test_server_line.hrl.
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Repeatedly reload a literals module while sending
the references literals around in a process ring.
This will smoke test the non-copying literals message sending does
not corrupt code unloading.
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Use the md5 of the native code chunk instead of the Beam code md5.
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We did not have test case that ensures that the loader refuses to
load a module if there already exists old code for the module.
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To simplify the implementation of literal pools (constant pools)
for the R12 release, a shortcut was taken regarding binaries --
all binaries would be stored as heap binaries regardless of size.
To allow a module containing literals to be unloaded, literal
terms are copied when sent to another process. That means that
huge literal binaries will also be copied if they are sent to
another process, which could be surprising.
Another problem is that the arity field in the header for the heap
object may not be wide enough to handle big binaries.
Therefore, bite the bullet and allow refc binaries to be stored
in literal pools. In short, the following need to be changed:
* Each loaded module needs a MSO list, linking all refc binaries
in the literal pool.
* When check_process_code/2 copies literals to a process heap,
it must link each referenced binary into the MSO list for the
process and increment the reference counter for the binary.
* purge_module/1 must decrement the reference counter for each
refc binary in the literal pool.
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* bjorn/fun-improvements/OTP-9667:
sys_pre_expand: Remove incorrect comment
compiler: Eliminate use of deprecated erlang:hash/2
beam_asm: Fix broken NewIndex in fun entries
beam_asm: Strenghten the calculation of Uniq for funs
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Funs are identified by a triple, <Module,Uniq,Index>, where Module is
the module name, Uniq is a 27 bit hash value of some intermediate
representation of the code for the fun, and index is a small integer.
When a fun is loaded, the triple for the fun will be compared to
previously loaded funs. If all elements in the triple in the newly
loaded fun are the same, the newly loaded fun will replace the previous
fun. The idea is that if Uniq are the same, the code for the fun is also
the same.
The problem is that Uniq is only based on the intermediate representation
of the fun itself. If the fun calls local functions in the same module,
Uniq may remain the same even if the behavior of the fun has been changed.
See
http://erlang.org/pipermail/erlang-bugs/2007-June/000368.htlm
for an example.
As a long-term plan to fix this problem, the NewIndex and NewUniq
fields was added to each fun in the R8 release (where NewUniq is the
MD5 of the BEAM code for the module). Unfortunately, it turns
out that the compiler does not assign unique value to NewIndex (if it
isn't tested, it doesn't work), so we cannot use the
<Module,NewUniq,NewIndex> triple as identification.
It would be possible to use <Module,NewUniq,Index>, but that seems
ugly. Therefore, fix the problem by making Uniq more unique by
taking 27 bits from the MD5 for the BEAM code. That only requires
a change to the compiler.
Also update a test case for cover, which now fails because of the
stronger Uniq calculation. (The comment in test case about why the
Pid2 process survived is not correct.)
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Currently, the external fun syntax "fun M:F/A" only supports
literals. That is, "fun lists:reverse/1" is allowed but not
"fun M:F/A".
In many real-life situations, some or all of M, F, A are
not known until run-time, and one is forced to either use
the undocumented erlang:make_fun/3 BIF or to use a
"tuple fun" (which is deprecated).
EEP-23 suggests that the parser (erl_parse) should immediately
transform "fun M:F/A" to "erlang:make_fun(M, F, A)". We have
not followed that approach in this implementation, because we
want the abstract code to mirror the source code as closely
as possible, and we also consider erlang:make_fun/3 to
be an implementation detail that we might want to remove in
the future.
Instead, we will change the abstract format for "fun M:F/A" (in a way
that is not backwards compatible), and while we are at it, we will
move the translation from "fun M:F/A" to "erlang:make_fun(M, F, A)"
from sys_pre_expand down to the v3_core pass. We will also update
the debugger and xref to use the new format.
We did consider making the abstract format backward compatible if
no variables were used in the fun, but decided against it. Keeping
it backward compatible would mean that there would be different
abstract formats for the no-variable and variable case, and tools
would have to handle both formats, probably forever.
Reference: http://www.erlang.org/eeps/eep-0023.html
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Add erlang:check_old_code/1 to quickly check whether a module
has old code. If there is no old code, there is no need to call
erlang:check_process_code/2 for all processes, which will save
some time if there are many processes.
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Causing out-of-memory on halfword emulator.
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