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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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#### 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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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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These allow one to hash VM terms from NIF code.
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# Conflicts:
# erts/emulator/test/nif_SUITE_data/nif_SUITE.c
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* egil/erts/nif-format_term/OTP-13580:
runtime_tools: Change erts_snprintf to enif_snprintf
erts: Document enif_snprintf
erts: Add tests for enif_snprintf
erts: Add enif_snprintf
Conflicts:
erts/emulator/beam/erl_nif_api_funcs.h
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- Termination of a process...
- Modify trace flags of process...
- Process info on process...
- Register/unregister of name on process...
- Set group leader on process...
... while it is executing a dirty NIF.
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* Add the capability to format erlang terms to a char buffer in nifs.
* Bump NIF version to 2.11
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* henrik/update-copyrightyear:
update copyright-year
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* Accept a raw data buffer instead of ErlNifBinary
* Accept option ERL_NIF_BIN2TERM_SAFE
* Return number of read bytes
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to read OS environment variables in a safe and portable way.
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Add enif_raise_exception function to allow NIFs to raise error
exceptions holding any Erlang terms. This does not replace or
deprecate the enif_make_badarg function, though, because raising
badarg errors is so idiomatic in NIFs. Reimplement enif_make_badarg on
top of enif_raise_exception. Add new tests for enif_raise_exception
for both normal and dirty NIFs. Add documentation for
enif_raise_exception.
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Sverker Eriksson came up with the following idea: to handle a future
ability for NIFs to raise more than just badarg exceptions, modify the
recently-added enif_has_pending_exception function to take a second
argument: a pointer to ERL_NIF_TERM. If this argument is a null
pointer, ignore it. Otherwise, if the first argument, an ErlNifEnv*,
has an associated exception, set the pointed-to ERL_NIF_TERM of the
second argument to the value of the exception term. Add new tests and
documentation for this modification.
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and add 'dirty_scheduler_support' to ErlNifSysInfo
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enif_schedule_nif() put LAST of the unconditional functions to keep the
order which is vital for ABI compatibility on Windows.
The conditional dirty scheduler stuff moved down at the end of the list
to keep them out of the way. We don't want them mess things up then they
become unconditional some day.
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In the #erlang IRC channel Anthony Ramine once mentioned the idea of
allowing a NIF to use an emulator trap, similar to a BIF trap, to schedule
another NIF for execution. This is exactly how dirty NIFs were implemented
for Erlang/OTP 17.0, so this commit refactors and generalizes that dirty
NIF code to support a new enif_schedule_nif() API function.
The enif_schedule_nif() function allows a long-running NIF to be broken
into separate NIF invocations. The NIF first executes part of the
long-running task, then calls enif_schedule_nif() to schedule a NIF for
later execution to continue the task. Any number of NIFs can be scheduled
in this manner, one after another. Since the emulator regains control
between invocations, this helps avoid problems caused by native code tying
up scheduler threads for too long.
The enif_schedule_nif() function also replaces the original experimental
dirty NIF API. The function takes a flags parameter that a caller can use
to indicate the NIF should be scheduled onto either a dirty CPU scheduler
thread, a dirty I/O scheduler thread, or scheduled as a regular NIF on a
regular scheduler thread. With this change, the original experimental
enif_schedule_dirty_nif(), enif_schedule_dirty_nif_finalizer() and
enif_dirty_nif_finalizer() API functions are no longer needed and have been
removed. Explicit scheduling of a dirty NIF finalization function is no
longer necessary; if an application wants similar functionality, it can
have a dirty NIF just invoke enif_schedule_nif() to schedule a non-dirty
NIF to complete its task.
Lift the restriction that dirty NIFs can't call enif_make_badarg() to raise
an exception. This was a problem with the original dirty NIF API because it
forced developers to get and check all incoming arguments in a regular NIF,
and then schedule the dirty NIF which then had to get all the arguments
again. Now, the argument checking can be done in the dirty NIF and it can
call enif_make_badarg() itself to flag incorrect arguments.
Extend the ErlNifFunc struct with a new flags field that allows NIFs to be
declared as dirty. The default value for this field is 0, indicating a
regular NIF, so it's backwards compatible with all existing statically
initialized ErlNifFunc struct instances, and so such instances require no
code changes. Defining the flags field with a value of
ERL_NIF_DIRTY_JOB_CPU_BOUND indicates that the NIF should execute on a
dirty CPU scheduler thread, or defining it with a value of
ERL_NIF_DIRTY_JOB_IO_BOUND indicates that the NIF should execute on a dirty
I/O scheduler thread. Any other flags field value causes a NIF library
loading error.
Extend the ErlNifEntry struct with a new options field that indicates
whether a NIF library was built with support for optional features such as
dirty NIFs. When a NIF library is loaded, the runtime checks the options
field to ensure compatibility. If a NIF library built with dirty NIF
support is loaded into a runtime that does not support dirty NIFs, and the
library defines one or more ErlNifFunc entries with non-zero flags fields
indicating dirty NIFs, a NIF library loading error results. There is no
error if a NIF library built with dirty NIF support is loaded into a
runtime that does not support dirty NIFs but the library does not have any
dirty NIFs. It is also not an error if a library without dirty NIF support
is loaded into a runtime built with dirty NIF support.
Add documentation and tests for enif_schedule_nif().
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as it does the same thing as enif_get_map_value.
Replace with placeholder to be ABI backward compatible on Windows
as long as enif_find_map_value is not called.
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- int enif_is_map(ErlNifEnv* env, ERL_NIF_TERM map)
- int enif_get_map_size(ErlNifEnv *env, ERL_NIF_TERM, int*)
- ERL_NIF_TERM enif_make_new_map(ErlNifEnv *env)
- int enif_make_map_put(ErlNifEnv *env, ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM value, ERL_NIF_TERM* map_out)
- int enif_get_map_value(ErlNifEnv *env, ERL_NIF_TERM map, ERL_NIF_TERM key, ERL_NIF_TERM* value)
- int enif_find_map_value(ErlNifEnv *env, ERL_NIF_TERM map, ERL_NIF_TERM key, ERL_NIF_TERM* value)
- int enif_make_map_update(ErlNifEnv *env, ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM value, ERL_NIF_TERM* map_out)
- int enif_make_map_remove(ErlNifEnv *env, ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM* map_out)
- int enif_map_iterator_create(ErlNifEnv *env, ERL_NIF_TERM map, ErlNifMapIterator *iter)
- void enif_map_iterator_destroy(ErlNifEnv *env, ErlNifMapIterator *iter)
- int enif_map_iterator_next(ErlNifEnv *env, ErlNifMapIterator *iter)
- int enif_map_iterator_get_pair(ErlNifEnv *env, ErlNifMapIterator *iter, ERL_NIF_TERM *key, ERL_NIF_TERM *value)
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Add initial support for dirty schedulers.
There are two types of dirty schedulers: CPU schedulers and I/O
schedulers. By default, there are as many dirty CPU schedulers as there are
normal schedulers and as many dirty CPU schedulers online as normal
schedulers online. There are 10 dirty I/O schedulers (similar to the choice
of 10 as the default for async threads).
By default, dirty schedulers are disabled and conditionally compiled
out. To enable them, you must pass --enable-dirty-schedulers to the
top-level configure script when building Erlang/OTP.
Current dirty scheduler support requires the emulator to be built with SMP
support. This restriction will be lifted in the future.
You can specify the number of dirty schedulers with the command-line
options +SDcpu (for dirty CPU schedulers) and +SDio (for dirty I/O
schedulers). The +SDcpu option is similar to the +S option in that it takes
two numbers separated by a colon: C1:C2, where C1 specifies the number of
dirty schedulers available and C2 specifies the number of dirty schedulers
online. The +SDPcpu option allows numbers of dirty CPU schedulers available
and dirty CPU schedulers online to be specified as percentages, similar to
the existing +SP option for normal schedulers. The number of dirty CPU
schedulers created and dirty CPU schedulers online may not exceed the
number of normal schedulers created and normal schedulers online,
respectively. The +SDio option takes only a single number specifying the
number of dirty I/O schedulers available and online. There is no support
yet for programmatically changing at run time the number of dirty CPU
schedulers online via erlang:system_flag/2. Also, changing the number of
normal schedulers online via erlang:system_flag(schedulers_online,
NewSchedulersOnline) should ensure that there are no more dirty CPU
schedulers than normal schedulers, but this is not yet implemented. You can
retrieve the number of dirty schedulers by passing dirty_cpu_schedulers,
dirty_cpu_schedulers_online, or dirty_io_schedulers to
erlang:system_info/1.
Currently only NIFs are able to access dirty scheduler
functionality. Neither drivers nor BIFs currently support dirty
schedulers. This restriction will be addressed in the future.
If dirty scheduler support is present in the runtime, the initial status
line Erlang prints before presenting its interactive prompt will include
the indicator "[ds:C1:C2:I]" where "ds" indicates "dirty schedulers", "C1"
indicates the number of dirty CPU schedulers available, "C2" indicates the
number of dirty CPU schedulers online, and "I" indicates the number of
dirty I/O schedulers.
Document The dirty NIF API in the erl_nif man page. The API closely follows
Rickard Green's presentation slides from his talk "Future Extensions to the
Native Interface", presented at the 2011 Erlang Factory held in the San
Francisco Bay Area. Rickard's slides are available online at
http://bit.ly/1m34UHB .
Document the new erl command-line options, the additions to
erlang:system_info/1, and also add the erlang:system_flag/2 dirty scheduler
documentation even though it's not yet implemented.
To determine whether the dirty NIF API is available, native code can check
to see whether the C preprocessor macro ERL_NIF_DIRTY_SCHEDULER_SUPPORT is
defined. To check if dirty schedulers are available at run time, native
code can call the boolean enif_have_dirty_schedulers() function, and Erlang
code can call erlang:system_info(dirty_cpu_schedulers), which raises
badarg if no dirty scheduler support is available.
Add a simple dirty NIF test to the emulator NIF suite.
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