[Feature #20590]
For better of for worse, fork(2) remain the primary provider of
parallelism in Ruby programs. Even though it's frowned uppon in
many circles, and a lot of literature will simply state that only
async-signal safe APIs are safe to use after `fork()`, in practice
most APIs work well as long as you are careful about not forking
while another thread is holding a pthread mutex.
One of the APIs that is known cause fork safety issues is `getaddrinfo`.
If you fork while another thread is inside `getaddrinfo`, a mutex
may be left locked in the child, with no way to unlock it.
I think we could reduce the impact of these problem by preventing
in for the most notorious and common cases, by locking around
`fork(2)` and known unsafe APIs with a read-write lock.
This commit changes how stack extents are calculated for both the main
thread and other threads. Ruby uses the address of a local variable as
part of the calculation for machine stack extents:
* pthreads uses it as a lower-bound on the start of the stack, because
glibc (and maybe other libcs) can store its own data on the stack
before calling into user code on thread creation.
* win32 uses it as an argument to VirtualQuery, which gets the extent of
the memory mapping which contains the variable
However, the local being used for this is actually too low (too close to
the leaf function call) in both the main thread case and the new thread
case.
In the main thread case, we have the `INIT_STACK` macro, which is used
for pthreads to set the `native_main_thread->stack_start` value. This
value is correctly captured at the very top level of the program (in
main.c). However, this is _not_ what's used to set the execution context
machine stack (`th->ec->machine_stack.stack_start`); that gets set as
part of a call to `ruby_thread_init_stack` in `Init_BareVM`, using the
address of a local variable allocated _inside_ `Init_BareVM`. This is
too low; we need to use a local allocated closer to the top of the
program.
In the new thread case, the lolcal is allocated inside
`native_thread_init_stack`, which is, again, too low.
In both cases, this means that we might have VALUEs lying outside the
bounds of `th->ec->machine.stack_{start,end}`, which won't be marked
correctly by the GC machinery.
To fix this,
* In the main thread case: We already have `INIT_STACK` at the right
level, so just pass that local var to `ruby_thread_init_stack`.
* In the new thread case: Allocate the local one level above the call to
`native_thread_init_stack` in `call_thread_start_func2`.
[Bug #20001]
fix
The implementation of `native_thread_init_stack` for the various
threading models can use the address of a local variable as part of the
calculation of the machine stack extents:
* pthreads uses it as a lower-bound on the start of the stack, because
glibc (and maybe other libcs) can store its own data on the stack
before calling into user code on thread creation.
* win32 uses it as an argument to VirtualQuery, which gets the extent of
the memory mapping which contains the variable
However, the local being used for this is actually allocated _inside_
the `native_thread_init_stack` frame; that means the caller might
allocate a VALUE on the stack that actually lies outside the bounds
stored in machine.stack_{start,end}.
A local variable from one level above the topmost frame that stores
VALUEs on the stack must be drilled down into the call to
`native_thread_init_stack` to be used in the calculation. This probably
doesn't _really_ matter for the win32 case (they'll be in the same
memory mapping so VirtualQuery should return the same thing), but
definitely could matter for the pthreads case.
[Bug #20001]
With M:N thread scheduler, the native thread (NT) related resources
should be freed when the NT is no longer needed. So the calling
`native_thread_destroy()` at the end of `is will be freed when
`thread_cleanup_func()` (at the end of Ruby thread) is not correct
timing. Call it when the corresponding Ruby thread is collected.
This patch introduce M:N thread scheduler for Ractor system.
In general, M:N thread scheduler employs N native threads (OS threads)
to manage M user-level threads (Ruby threads in this case).
On the Ruby interpreter, 1 native thread is provided for 1 Ractor
and all Ruby threads are managed by the native thread.
From Ruby 1.9, the interpreter uses 1:1 thread scheduler which means
1 Ruby thread has 1 native thread. M:N scheduler change this strategy.
Because of compatibility issue (and stableness issue of the implementation)
main Ractor doesn't use M:N scheduler on default. On the other words,
threads on the main Ractor will be managed with 1:1 thread scheduler.
There are additional settings by environment variables:
`RUBY_MN_THREADS=1` enables M:N thread scheduler on the main ractor.
Note that non-main ractors use the M:N scheduler without this
configuration. With this configuration, single ractor applications
run threads on M:1 thread scheduler (green threads, user-level threads).
`RUBY_MAX_CPU=n` specifies maximum number of native threads for
M:N scheduler (default: 8).
This patch will be reverted soon if non-easy issues are found.
[Bug #19842]
```
1) Failure:
TestThreadInstrumentation#test_thread_instrumentation [/tmp/ruby/src/trunk-repeat20-asserts/test/-ext-/thread/test_instrumentation_api.rb:33]:
Call counters[4]: [3, 4, 4, 4, 0].
Expected 0 to be > 0.
```
We fire the EXIT hook after the call to `thread_sched_to_dead` which
mean another thread might be running before the `EXIT` hook have been
executed.
fiber machine stack is placed outside of C stack allocated by wasm-ld,
so highest stack address recorded by `rb_wasm_record_stack_base` is
invalid when running on non-main fiber.
Therefore, we should scan `stack_{start,end}` which always point a valid
stack range in any context.
[Feature #18339]
After experimenting with the initial version of the API I figured there is a need
for an exit event to cleanup instrumentation data. e.g. if you record data in a
{thread_id -> data} table, you need to free associated data when a thread goes away.
`NON_SCALAR_THREAD_ID` shows `pthread_t` is non-scalar (non-pointer)
and only s390x is known platform. However, the supporting code is
very complex and it is only used for deubg print information.
So this patch removes the support of `NON_SCALAR_THREAD_ID`
and make the code simple.
`rb_thread_t` contained `native_thread_data_t` to represent
thread implementation dependent data. This patch separates
them and rename it `rb_native_thread` and point it from
`rb_thraed_t`.
Now, 1 Ruby thread (`rb_thread_t`) has 1 native thread (`rb_native_thread`).
Now GVL is not process *Global* so this patch try to use
another words.
* `rb_global_vm_lock_t` -> `struct rb_thread_sched`
* `gvl->owner` -> `sched->running`
* `gvl->waitq` -> `sched->readyq`
* `rb_gvl_init` -> `rb_thread_sched_init`
* `gvl_destroy` -> `rb_thread_sched_destroy`
* `gvl_acquire` -> `thread_sched_to_running` # waiting -> ready -> running
* `gvl_release` -> `thread_sched_to_waiting` # running -> waiting
* `gvl_yield` -> `thread_sched_yield`
* `GVL_UNLOCK_BEGIN` -> `THREAD_BLOCKING_BEGIN`
* `GVL_UNLOCK_END` -> `THREAD_BLOCKING_END`
* removed
* `rb_ractor_gvl`
* `rb_vm_gvl_destroy` (not used)
There are GVL functions such as `rb_thread_call_without_gvl()` yet
but I don't have good name to replace them. Maybe GVL stands for
"Greate Valuable Lock" or something like that.
Jean Boussier
Nobuyoshi Nakada
Koichi Sasada
KJ Tsanaktsidis
Jean Boussier
Yuta Saito