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Communication between Erlang processes has conceptually always been
performed through asynchronous signaling. The runtime system
implementation has however previously preformed most operation
synchronously. In a system with only one true thread of execution, this
is not problematic (often the opposite). In a system with multiple threads
of execution (as current runtime system implementation with SMP support)
it becomes problematic. This since it often involves locking of structures
when updating them which in turn cause resource contention. Utilizing
true asynchronous communication often avoids these resource contention
issues.
The case that triggered this change was contention on the link lock due
to frequent updates of the monitor trees during communication with a
frequently used server. The signal order delivery guarantees of the
language makes it hard to change the implementation of only some signals
to use true asynchronous signaling. Therefore the implementations
of (almost) all signals have been changed.
Currently the following signals have been implemented as true
asynchronous signals:
- Message signals
- Exit signals
- Monitor signals
- Demonitor signals
- Monitor triggered signals (DOWN, CHANGE, etc)
- Link signals
- Unlink signals
- Group leader signals
All of the above already defined as asynchronous signals in the
language. The implementation of messages signals was quite
asynchronous to begin with, but had quite strict delivery constraints
due to the ordering guarantees of signals between a pair of processes.
The previously used message queue partitioned into two halves has been
replaced by a more general signal queue partitioned into three parts
that service all kinds of signals. More details regarding the signal
queue can be found in comments in the erl_proc_sig_queue.h file.
The monitor and link implementations have also been completely replaced
in order to fit the new asynchronous signaling implementation as good
as possible. More details regarding the new monitor and link
implementations can be found in the erl_monitor_link.h file.
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This does not avoid allocating a ProcBin since we still need to
release the binary somehow (and using the tmp obj list is slightly
slower since it's an unavoidable off-heap allocation), but it does give
us a hard limit on how long said ProcBin will live, which is a lot
better than before.
OTP-14845
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This fixes two corner-cases:
1) We will no longer return an invalid term when a binary inspected
on environment A is used in enif_make_binary on environment B
2) A double-free in this sequence of events:
* enif_alloc_binary(size, &bin);
* enif_ioq_enq_binary(ioq, &bin, skip);
* enif_make_binary(env, &bin);
* enif_make_binary(env, &bin);
OTP-14931
OTP-14932
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Attaching to a ProcBin is the fastest way to delay the release of an
already allocated Binary, but alloc_tmp_obj is a lot faster when
starting from scratch since it usually uses temp_alloc.
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When a dirty NIF is executed a "schedule in" trace event is
generated, which may in turn result in a generic system task being
created, causing the process to be scheduled out as it can't run
dirty with pending tasks.
This is usually fine since said system task is seldom created, but
ERTS_FORCE_ENIF_SEND_DELAY was de-facto always on for debug builds,
causing the process to bounce between dirty and normal schedulers
forever.
This commit is not a complete fix and it can go off the rails even
on normal builds; if there's a lot of dirty jobs lined up and the
receiver's msgq lock happens to be busy at the wrong time, the
additional trace messages generated through this will hammer the
lock and keep everything bouncing.
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This introduces a way to retrieve erlang terms from NIF IO queues
without having to resort to copying.
OTP-14797
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Break out from 'flags' into new dedicated 'connection_id'
just for simplicity.
Also changed flags to low bits
and that affected enif_binary_to_term.
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when done by enif_free_env or enif_clear_env.
Do check before we free heap fragments.
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* maint:
Updated OTP version
Update release notes
Update version numbers
inets: Prepare for release
inets: Add missing guard
Avoid WindowBits=8 as per the manual
Fix deflateParams on zlib 1.2.11
Ignore empty binaries in enif_inspect_iovec
Emasculate writable binaries on entering an iovec
Only apply EOS behaviors if there's pending data
Conflicts:
OTP_VERSION
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The lack of this caused serious data corruption when a binary was
altered after entering the queue. This went unnoticed because it
was never used without erlang:iolist_to_iovec, which always
emasculates binaries.
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The BeamOp() macro in erl_vm.h is clumsy to use. All users
cast the return value to BeamInstr.
Define new macros that are easier to use. In the future,
we might want to pack an operand into the same word as
the pointer to the instruction, so we will define two macros.
BeamIsOpCode() is used to rewrite code like this:
if (Instr == (BeamInstr) BeamOp(op_i_func_info_IaaI) {
...
}
to:
if (BeamIsOpCode(Instr, op_i_func_info_IaaI)) {
...
}
BeamOpCodeAddr(op_apply_bif) is used when we need the address
for an instruction.
Also elimiminate the global variables em_* in beam_emu.c.
They are not really needed. Use the BeamOpCodeAddr() macro
instead.
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Besides being noisy, they were already defined by a global Unix-
specific header, causing the Windows build to fail if one forgot to
define them.
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OTP-14520
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Conflicts:
erts/emulator/beam/erl_nif.c
erts/emulator/beam/erl_process.c
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* lukas/erts/fix_dirty_trace_message_flush/OTP-14538:
erts: Must have main lock when flushing trace messages
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* sverker/enif_whereis-bug:
erts: Fix bug in enif_whereis_pid/port
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This refactor was done using the unifdef tool like this:
for file in $(find erts/ -name *.[ch]); do unifdef -t -f defile -o $file $file; done
where defile contained:
#define ERTS_SMP 1
#define USE_THREADS 1
#define DDLL_SMP 1
#define ERTS_HAVE_SMP_EMU 1
#define SMP 1
#define ERL_BITS_REENTRANT 1
#define ERTS_USE_ASYNC_READY_Q 1
#define FDBLOCK 1
#undef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
#define ERTS_POLL_ASYNC_INTERRUPT_SUPPORT 0
#define ERTS_POLL_USE_WAKEUP_PIPE 1
#define ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE 1
#undef ERTS_HAVE_PLAIN_EMU
#undef ERTS_SIGNAL_STATE
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that could cause heap corruption if
whereis lookup conflicts with other register updater
AND other thread sends on-heap message while main lock is released.
Also improved enif_whereis from dirty nifs by passing c_p as NULL.
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* john/erts/runtime-lcnt:
Document rt_mask and add warnings about copy_save
Add an emulator test suite for lock counting
Break erts_debug:lock_counters/1 into separate BIFs
Allow toggling lock counting at runtime
Move lock flags to a common header
Enable register_SUITE for lcnt builds
Enable lcnt smoke test on all builds that have lcnt enabled
Make lock counter info independent of the locks being counted
OTP-14412
OTP-13170
OTP-14413
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The implementation is still hidden behind ERTS_ENABLE_LOCK_COUNT, and
all categories are still enabled by default, but the actual counting can be
toggled at will.
OTP-13170
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If we don't have the main lock, multiple threads may come in and
do the flush at the same time which will lead to all kinds of
strang problems.
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#### Why do we need this new feature?
There are cases when a NIF needs to send a message, using `enif_send()`, to a long-lived process with a registered name.
A common use-case is logging, where asynchronous fire-and-forget messages are the norm.
There can also be cases where a yielding or dirty NIF or background thread may request a callback from a service with additional information it needs to complete its operation, yielding or waiting (with suitable timeouts, etc) until its state has been updated through the NIF module's API.
NIFs can only send messages to pids, and the lack of name resolution leaves a complicated dance between separate monitoring processes and the NIF as the only way to keep a NIF informed of the whereabouts of such long-lived processes.
Providing a reliable, built-in facility for NIFs to resolve process (or port) names simplifies these use cases considerably.
#### Risks or uncertain artifacts?
Testing has not exposed any significant risk.
The implementation behaves as expected on regular and dirty scheduler threads as well as non-scheduler threads.
By constraining the `enif_whereis_...()` functions to their minimal scopes and using patterns consistent with related functions, the implementation, testing, and maintenance burden is low.
The API and behavior of existing functions is unchanged.
#### How did you solve it?
While extending `enif_send()` to operate on a pid or an atom (as `erlang:send/2` does) was attractive, it would have entailed changing the type of its `to_pid` parameter and thereby breaking backward compatibility.
The same consideration applies to `enif_port_command()`.
That leaves a choice between 1, 2, or 3 new functions:
1. `enif_whereis()`
2. `enif_whereis_pid()` and `enif_whereis_port()`
3. All of the above.
While option (1), directly mimicking the behavior of `erlang:whereis/1`, is appealing, it poses potential problems if `pid()` or `port()` are subsequently implemented as non-integral types that must be bound to an owning `ErlNifEnv` instance.
Therefore, option (2) has been chosen to use `ErlNifPid`/`ErlNifPort` structures in the API to maintain proper term ownership semantics.
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Support hashing terms from NIF code
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* sverker/refactor:
erts: Introduce struct binary_internals
erts: Introduce erts_bin_release
erts: Init refc=1 in erts_bin_drv_alloc*
erts: Init refc=1 in erts_bin_nrml_alloc
erts: Remove deliberate leak of hipe fun entries
erts: Remove hipe_bifs:remove_refs_from/1
Refactor hipe specific code to use ErtsCodeInfo
erts: Refactor ErtsCodeInfo.native
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Allow for expanding support to 64-bit hashes without breaking the
interface.
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A more generic hashing function which can also hash terms based on
`make_internal_hash'.
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