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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The previously used message queue partitioned into two halves has been
replaced by a more general signal queue partitioned into three parts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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Replace long long with Uint64
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Example symptom:
1> float_to_list(0.145, [{decimals,1}]).
"0.2"
There were two problems in sys_double_to_chars_fast
1. Most serious was adding 0.55555555 / (10^D) instead of 0.5 / (10^D)
which imposed a 5.5% risk of a faulty rounding up.
2. Using fixpoint for frac_part which lost significant bits if F < 0.5
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putenv(3) and friends aren't thread-safe regardless of how you slice
it; a global lock around all environment operations (like before)
keeps things safe as far as our own operations go, but we have
absolutely no control over what libc or a library dragged in by a
driver/NIF does -- they're free to call getenv(3) or putenv(3)
without honoring our lock.
This commit solves this by setting up an "emulated" environment which
can't be touched without going through our interfaces. Third-party
libraries can still shoot themselves in the foot but benign uses of
os:putenv/2 will no longer risk crashing the emulator.
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kqueue is broken on earlier versions of OS X.
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that is shared between _kp and _nkp versions.
Makes it easier to access in debugger.
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# Conflicts:
# erts/emulator/beam/erl_process.c
# erts/emulator/beam/sys.h
# erts/emulator/sys/common/erl_check_io.c
# erts/emulator/sys/common/erl_check_io.h
# erts/emulator/sys/unix/sys.c
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by having different structs with same name.
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and use correct cache alignment.
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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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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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The macro previously named 'LOG2' is in fact computing the LSB (not the MSB)
of its input, and can only be used to compute log2(n) when n is is a power
of 2, that is, when its LSB is also its MSB.
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erl_mseg.c: don't use invalid indices in - > cache_powered_node[]
OTP-14360
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Allocations and message sending are now scheduled by a signal,
via a signal state bitmap, instead of doing it directly in the signal handler.
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The signal handler will now schedule a sigterm message instead of sending
the message in the signal handler. The signal handler must refrain from
memory allocations and thus the event is scheduled.
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Why did I add that?
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Conflicts:
erts/emulator/beam/erl_binary.h
erts/emulator/beam/erl_monitors.c
erts/emulator/beam/erl_nif.c
erts/emulator/beam/global.h
erts/emulator/test/nif_SUITE_data/nif_SUITE.c
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by simply disable "delayed deselect".
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to negative int as error and positive as success.
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indentation and comments only
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as it's not part of the API
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to not inline cold reallocation code.
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