Acme-Parataxis
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lib/Acme/Parataxis.c view on Meta::CPAN
/**
* @file Parataxis.c
* @brief Low-level Green Threads (Fibers) and Hybrid Thread Pool for Perl.
*
* @section Overview
* This file implements a cooperative multitasking system (Fibers) integrated
* with a preemptive native thread pool. It allows Perl to run thousands of
* user-mode fibers that can offload blocking C-level tasks to background
* OS threads without stalling the main interpreter.
*
* @section Architecture
* - **Fibers**: The primitive unit of execution. Each fiber has its own OS context
* and a complete set of Perl interpreter stacks (Argument, Mark, Scope, Save, Mortal).
* - **Coroutines**: The execution pattern (yield/call/transfer) used by fibers to
* pass control.
* - **Thread Pool**: A fixed pool of worker threads that poll a job queue for
* blocking operations like sleep, I/O, or heavy computation.
* - **Context Switching**: The `swap_perl_state` function manually saves and restores
* the global state of the Perl interpreter (`PL_*` variables) to allow disjoint
* execution flows.
*
* @section Caveats
* Shared subroutines (CVs) with re-entrant yielding calls are handled by a
* specialized pad-clearing mechanism in `_activate_current_depths` to satisfy
* Perl's internal `AvFILLp` assertions in debug builds.
*/
#ifdef _WIN32
#define WIN32_LEAN_AND_MEAN
#ifndef _WIN32_WINNT
#define _WIN32_WINNT 0x0601
#endif
#else
#ifndef _XOPEN_SOURCE
#define _XOPEN_SOURCE 600
#endif
#ifdef __APPLE__
#ifndef _DARWIN_C_SOURCE
#define _DARWIN_C_SOURCE
#endif
#endif
#endif
#define PERL_NO_GET_CONTEXT
#define NO_XSLOCKS
#include "EXTERN.h"
#include "XSUB.h"
#include "perl.h"
#ifdef _WIN32
/** @brief Export macro for Windows DLLs */
#define DLLEXPORT __declspec(dllexport)
/** @brief Handle for the underlying OS fiber context */
typedef LPVOID coro_handle_t;
/** @brief Handle for a native OS thread */
typedef HANDLE para_thread_t;
/** @brief Mutex type for queue synchronization */
typedef CRITICAL_SECTION para_mutex_t;
#define LOCK(m) EnterCriticalSection(&m)
#define UNLOCK(m) LeaveCriticalSection(&m)
#define LOCK_INIT(m) InitializeCriticalSection(&m)
#else
#include <pthread.h>
#include <sched.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <ucontext.h>
#include <unistd.h>
#if defined(__APPLE__) || defined(__FreeBSD__)
#include <sys/sysctl.h>
#include <sys/types.h>
#endif
/** @brief Export macro for Unix systems */
#define DLLEXPORT __attribute__((visibility("default")))
/** @brief Handle for the underlying OS fiber context (ucontext_t) */
typedef ucontext_t coro_handle_t;
/** @brief Handle for a native OS thread (pthread_t) */
lib/Acme/Parataxis.c view on Meta::CPAN
nm[0] = CTL_HW;
nm[1] = HW_NCPU;
sysctl(nm, 2, &count, &len, NULL, 0);
return (count > 0) ? (int)count : 1;
#else
long count = sysconf(_SC_NPROCESSORS_ONLN);
return (count > 0) ? (int)count : 1;
#endif
}
/**
* @struct para_fiber_t
* @brief The complete execution context of a Perl Fiber.
*
* This structure encapsulates both the OS-level register state (via context)
* and the entire internal state of the Perl interpreter required to pause
* and resume execution of Perl code.
*/
typedef struct {
coro_handle_t context; /**< OS-specific context handle */
#ifndef _WIN32
void * stack_p; /**< Pointer to dynamically allocated fiber stack (Unix only) */
size_t stack_sz; /**< Size of the allocated stack (Unix only) */
#endif
/*
* Perl Interpreter State Pointers.
* These must be saved and restored during every context switch.
*/
PERL_SI * si; /**< Current Stack Info (tracks recursion and eval frames) */
AV * curstack; /**< The active Argument Stack (AV*) */
SSize_t stack_sp_offset; /**< Stack Pointer offset from stack base */
I32 * markstack; /**< Base of the Mark Stack (tracks list start points) */
I32 * markstack_ptr; /**< Current pointer into the Mark Stack */
I32 * markstack_max; /**< Limit of the Mark Stack */
I32 * scopestack; /**< Base of the Scope Stack (tracks block nesting) */
I32 scopestack_ix; /**< Current index in the Scope Stack */
I32 scopestack_max; /**< Limit of the Scope Stack */
ANY * savestack; /**< Base of the Save Stack (tracks local/my variables for cleanup) */
I32 savestack_ix; /**< Current index in the Save Stack */
I32 savestack_max; /**< Limit of the Save Stack */
SV ** tmps_stack; /**< Base of the Mortal Stack (tracks SVs needing refcnt decrement) */
I32 tmps_ix; /**< Current index in the Mortal Stack */
I32 tmps_floor; /**< Current floor of the Mortal Stack */
I32 tmps_max; /**< Limit of the Mortal Stack */
JMPENV * top_env; /**< Pointer to the top exception environment (eval/die buffers) */
COP * curcop; /**< Current Op Pointer (location in the source/bytecode) */
OP * op; /**< Current Operation being executed */
PAD * comppad; /**< Current lexical Pad (variable storage) */
SV ** curpad; /**< Array pointer to the current lexical Pad */
PMOP * curpm; /**< Current pattern match state */
PMOP * curpm_under; /**< Current pattern match state under */
PMOP * reg_curpm; /**< Current regex match state */
GV * defgv; /**< The $_ global */
GV * last_in_gv; /**< GV used in last <FH> */
SV * rs; /**< The $/ global */
GV * ofsgv; /**< The $, global */
SV * ors_sv; /**< The $\ global */
GV * defoutgv; /**< The default output filehandle */
HV * curstash; /**< Current package stash */
HV * defstash; /**< Default package stash */
SV * errors; /**< Outstanding queued errors */
SV * user_cv; /**< The Perl sub/coderef this fiber is running */
SV * self_ref; /**< The Acme::Parataxis Perl object wrapper */
SV * transfer_data; /**< Arguments or return values passed during yield/transfer */
int id; /**< Numeric ID of this fiber */
int finished; /**< Flag: 1 if the fiber has completed its entry_point */
int parent_id; /**< ID of the fiber that 'called' this one (asymmetric) */
int last_sender; /**< ID of the fiber that last switched control to this one */
} para_fiber_t;
/** @name Job Status Constants */
///@{
#define JOB_FREE 0 /**< Slot is available for new tasks */
#define JOB_NEW 1 /**< Task is submitted but not yet picked up by a worker */
#define JOB_BUSY 2 /**< Task is currently being processed by a worker thread */
#define JOB_DONE 3 /**< Task has completed and results are ready */
///@}
/** @name Task Type Constants */
///@{
#define TASK_SLEEP 0 /**< Sleep for N milliseconds */
#define TASK_GET_CPU 1 /**< Retrieve current core ID */
#define TASK_READ 2 /**< Wait for read-readiness on a file descriptor */
#define TASK_WRITE 3 /**< Wait for write-readiness on a file descriptor */
///@}
/**
* @union value_t
* @brief Generic container for task input/output data.
*/
typedef union {
int64_t i; /**< Integer/Pointer storage */
double d; /**< Floating point storage */
char * s; /**< String storage */
} value_t;
/**
* @struct job_t
* @brief Represents a task in the background thread pool queue.
*/
typedef struct {
int fiber_id; /**< ID of the Fiber that submitted this task */
int target_thread; /**< Index of the assigned worker thread */
int type; /**< Type of task to perform (TASK_*) */
value_t input; /**< Input data for the task */
value_t output; /**< Result data populated by the worker */
int timeout_ms; /**< Timeout duration for I/O tasks */
int status; /**< Current lifecycle state (JOB_*) */
} job_t;
// Global Registry and State
/** @brief Maximum number of concurrent fibers allowed */
#define MAX_FIBERS 1024
lib/Acme/Parataxis.c view on Meta::CPAN
}
return &PL_sv_undef;
}
/**
* @brief Restores subroutine call depths and cleans argument pads.
*
* This function iterates the context stack and restores CvDEPTH for
* active subroutines in two passes to safely handle recursive calls.
*
* Pass 1: Restores CvDEPTH for all active frames.
* Pass 2: Surgicaly cleans Slot 0 of the *next* pad depth for each CV.
*
* @param to The fiber being resumed.
*/
static void _activate_current_depths(pTHX_ para_fiber_t * to) {
PERL_SI * si = to->si;
if (!si || !si->si_cxstack)
return;
/* Pass 1: Restore CvDEPTH for all active frames */
for (I32 i = 0; i <= si->si_cxix; i++) {
PERL_CONTEXT * cx = &(si->si_cxstack[i]);
if (CxTYPE(cx) == CXt_SUB || CxTYPE(cx) == CXt_FORMAT) {
CV * cv = cx->blk_sub.cv;
if (cv && SvTYPE((SV *)cv) == SVt_PVCV)
CvDEPTH(cv) = cx->blk_sub.olddepth + 1;
}
}
/* Pass 2: Clean the landing pads for the NEXT call in each CV */
for (I32 i = 0; i <= si->si_cxix; i++) {
PERL_CONTEXT * cx = &(si->si_cxstack[i]);
if (CxTYPE(cx) == CXt_SUB || CxTYPE(cx) == CXt_FORMAT) {
CV * cv = cx->blk_sub.cv;
if (cv && SvTYPE((SV *)cv) == SVt_PVCV) {
PADLIST * pl = CvPADLIST(cv);
I32 next_depth = CvDEPTH(cv) + 1;
if (pl && next_depth <= PadlistMAX(pl)) {
AV * next_pad = (AV *)PadlistARRAY(pl)[next_depth];
if (next_pad && SvTYPE(next_pad) == SVt_PVAV) {
SV ** array = AvARRAY(next_pad);
if (array && AvMAX(next_pad) >= 0) {
SV * args = array[0];
if (args && SvTYPE(args) == SVt_PVAV) {
AvFILLp((AV *)args) = -1;
AvREAL_off((AV *)args);
}
}
}
}
}
}
}
}
/**
* @brief Swaps the internal Perl Interpreter state pointers.
*
* This is the core of the fiber implementation. It manually saves all
* global pointers that define the "state" of the Perl virtual machine for
* the current context and restores them for the target context.
*
* @param from Context being paused.
* @param to Context being resumed.
*/
void swap_perl_state(para_fiber_t * from, para_fiber_t * to) {
dTHX;
/* Save current state into 'from' context */
from->si = PL_curstackinfo;
// The Argument Stack (Main Perl stack)
from->curstack = PL_curstack;
from->stack_sp_offset = PL_stack_sp - PL_stack_base;
// The Mark Stack (Tracks where lists begin on the argument stack)
from->markstack = PL_markstack;
from->markstack_ptr = PL_markstack_ptr;
from->markstack_max = PL_markstack_max;
// The Scope Stack (Tracks block entry/exit for cleanup)
from->scopestack = PL_scopestack;
from->scopestack_ix = PL_scopestack_ix;
from->scopestack_max = PL_scopestack_max;
// The Save Stack (Tracks 'local' variables and destructors)
from->savestack = PL_savestack;
from->savestack_ix = PL_savestack_ix;
from->savestack_max = PL_savestack_max;
// The Mortal Stack (Tracks temporary SVs that need decrementing)
from->tmps_stack = PL_tmps_stack;
from->tmps_ix = PL_tmps_ix;
from->tmps_floor = PL_tmps_floor;
from->tmps_max = PL_tmps_max;
// Exception Environment (setjmp/longjmp buffers for eval/die)
from->top_env = PL_top_env;
// Op and Pad pointers (Where we are in the bytecode)
from->curcop = PL_curcop;
from->op = PL_op;
from->comppad = PL_comppad;
from->curpad = PL_curpad;
from->curpm = PL_curpm;
from->curpm_under = PL_curpm_under;
from->reg_curpm = PL_reg_curpm;
from->defgv = PL_defgv;
from->last_in_gv = PL_last_in_gv;
from->rs = PL_rs;
from->ofsgv = PL_ofsgv;
from->ors_sv = PL_ors_sv;
from->defoutgv = PL_defoutgv;
from->curstash = PL_curstash;
from->defstash = PL_defstash;
from->errors = PL_errors;
/* Load target state from 'to' context */
PL_curstackinfo = to->si;
PL_curstack = to->curstack;
lib/Acme/Parataxis.c view on Meta::CPAN
PL_curpad = to->curpad;
// Restore CvDEPTH and clean landing pads
_activate_current_depths(aTHX_ to);
}
/**
* @brief Allocates and initializes new Perl stacks for a fiber.
*
* Each fiber needs a complete set of independent stacks (Argument, Mark,
* Scope, Save, Mortal) to function as a separate execution thread.
*
* @param c The fiber context to initialize.
*/
void init_perl_stacks(para_fiber_t * c) {
dTHX;
// Allocate Stack Info (SI)
Newxz(c->si, 1, PERL_SI);
c->si->si_cxmax = 64;
// Use Newxz to ensure the context stack is zeroed.
Newxz(c->si->si_cxstack, c->si->si_cxmax, PERL_CONTEXT);
c->si->si_cxix = -1;
c->si->si_type = PERLSI_MAIN;
// Allocate Argument Stack (AV)
c->curstack = newAV();
AvREAL_off(c->curstack); // Stacks do not 'own' their elements in the refcnt sense
av_extend(c->curstack, 128);
// Initialize stack with a dummy undef at index 0, matching Perl's main stack
AvARRAY(c->curstack)[0] = &PL_sv_undef;
AvFILLp(c->curstack) = 0;
c->stack_sp_offset = 0;
// Link the SI to the AV. Perl uses this linkage during stack unwinding.
c->si->si_stack = c->curstack;
// Allocate Control Stacks
I32 sz = 2048; /* Recursion depth support */
Newx(c->markstack, sz, I32);
c->markstack_ptr = c->markstack;
*c->markstack_ptr = 0;
c->markstack_max = c->markstack + sz - 1;
Newx(c->scopestack, sz, I32);
c->scopestack_ix = 0;
c->scopestack_max = sz;
Newx(c->savestack, sz, ANY);
c->savestack_ix = 0;
c->savestack_max = sz;
Newx(c->tmps_stack, sz, SV *);
c->tmps_ix = -1;
c->tmps_floor = -1;
c->tmps_max = sz;
// Inherit initial globals from current interpreter state
c->curcop = PL_curcop;
c->op = PL_op;
c->top_env = PL_top_env;
c->curpm = PL_curpm;
c->curpm_under = PL_curpm_under;
c->reg_curpm = NULL;
c->defgv = PL_defgv;
c->last_in_gv = PL_last_in_gv;
c->rs = PL_rs;
c->ofsgv = PL_ofsgv;
c->ors_sv = PL_ors_sv;
c->defoutgv = PL_defoutgv;
c->curstash = PL_curstash;
c->defstash = PL_defstash;
c->errors = PL_errors;
// Start with fresh pads to avoid interfering with caller.
c->comppad = NULL;
c->curpad = NULL;
}
/**
* @brief Initializes the fiber system and converts the main thread.
*
* This function must be called once before any other fiber operations.
* It captures the state of the main Perl interpreter thread.
*
* @return int 0 on success.
*/
DLLEXPORT int init_system() {
dTHX;
if (system_initialized)
return 0;
if (max_thread_pool_size == 0) {
max_thread_pool_size = get_cpu_count();
if (max_thread_pool_size > MAX_THREADS)
max_thread_pool_size = MAX_THREADS;
}
main_context.si = PL_curstackinfo;
main_context.transfer_data = &PL_sv_undef;
main_context.id = -1;
main_context.finished = 0;
main_context.last_sender = -1;
main_context.curpm = PL_curpm;
main_context.curpm_under = PL_curpm_under;
main_context.reg_curpm = PL_reg_curpm;
main_context.defgv = PL_defgv;
main_context.last_in_gv = PL_last_in_gv;
main_context.rs = PL_rs;
main_context.ofsgv = PL_ofsgv;
main_context.ors_sv = PL_ors_sv;
main_context.defoutgv = PL_defoutgv;
main_context.curstash = PL_curstash;
main_context.defstash = PL_defstash;
main_context.errors = PL_errors;
system_initialized = 1;
#ifdef _WIN32
/* Convert the main thread into a fiber so it can be switched out */
if (!main_fiber_handle) {
main_fiber_handle = ConvertThreadToFiber(NULL);
lib/Acme/Parataxis.c view on Meta::CPAN
}
if (c->self_ref && c->self_ref != &PL_sv_undef) {
SvREFCNT_dec(c->self_ref);
c->self_ref = NULL;
}
if (c->transfer_data && c->transfer_data != &PL_sv_undef) {
SvREFCNT_dec(c->transfer_data);
c->transfer_data = NULL;
}
/* Early exit if Perl is already shutting down */
if (PL_dirty) {
#ifndef _WIN32
if (c->stack_p)
free(c->stack_p);
#endif
free(c);
return;
}
#ifdef _WIN32
if (c->context)
DeleteFiber(c->context);
#else
if (c->stack_p)
free(c->stack_p);
#endif
/* Safely free Perl-allocated stacks */
if (c->si) {
if (c->si->si_cxstack)
Safefree(c->si->si_cxstack);
Safefree(c->si);
}
if (c->curstack) {
av_clear(c->curstack);
SvREFCNT_dec((SV *)c->curstack);
c->curstack = NULL;
}
if (c->markstack)
Safefree(c->markstack);
if (c->scopestack)
Safefree(c->scopestack);
if (c->savestack)
Safefree(c->savestack);
if (c->tmps_stack) {
for (I32 i = 0; i <= c->tmps_ix; i++) {
SV * sv = c->tmps_stack[i];
if (sv && sv != &PL_sv_undef)
SvREFCNT_dec(sv);
}
Safefree(c->tmps_stack);
}
free(c);
}
/**
* @brief Global cleanup function for the fiber and thread pool system.
*
* Signals all worker threads to terminate and destroys all remaining
* fibers. Should be called during global destruction or system shutdown.
*/
DLLEXPORT void cleanup() {
dTHX;
if (threads_initialized) {
LOCK(queue_lock);
threads_keep_running = 0;
PARA_COND_BROADCAST(queue_cond);
UNLOCK(queue_lock);
#ifdef _WIN32
/* Wait for threads to finish and close handles */
for (int i = 0; i < current_thread_count; i++) {
if (thread_handles[i]) {
WaitForSingleObject(thread_handles[i], 100);
CloseHandle(thread_handles[i]);
thread_handles[i] = NULL;
}
}
#else
/* Give threads a moment to notice threads_keep_running = 0 */
usleep(10000);
#endif
}
if (current_fiber_id != -1) {
swap_perl_state(fibers[current_fiber_id], &main_context);
current_fiber_id = -1;
}
for (int i = 0; i < MAX_FIBERS; i++)
if (fibers[i])
destroy_coro(i);
if (main_context.transfer_data && main_context.transfer_data != &PL_sv_undef) {
SvREFCNT_dec(main_context.transfer_data);
main_context.transfer_data = &PL_sv_undef;
}
}
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