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signals-unix.c
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// This file is a part of Julia. License is MIT: https://julialang.org/license
// Note that this file is `#include`d by "signal-handling.c"
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <pthread.h>
#include <time.h>
#include <errno.h>
#if defined(_OS_DARWIN_) && !defined(MAP_ANONYMOUS)
#define MAP_ANONYMOUS MAP_ANON
#endif
#ifdef __APPLE__
#include <AvailabilityMacros.h>
#ifdef MAC_OS_X_VERSION_10_9
#include <sys/_types/_ucontext64.h>
#else
#define __need_ucontext64_t
#include <machine/_structs.h>
#endif
#endif
// Figure out the best signals/timers to use for this platform
#if defined(__APPLE__) // Darwin's mach ports allow signal-free thread management
#define HAVE_MACH
#define HAVE_KEVENT
#elif defined(__OpenBSD__)
#define HAVE_KEVENT
#else // generic Linux or FreeBSD
#define HAVE_TIMER
#endif
#ifdef HAVE_KEVENT
#include <sys/event.h>
#endif
// 8M signal stack, same as default stack size (though we barely use this)
static const size_t sig_stack_size = 8 * 1024 * 1024;
#include "julia_assert.h"
// helper function for returning the unw_context_t inside a ucontext_t
// (also used by stackwalk.c)
bt_context_t *jl_to_bt_context(void *sigctx)
{
#ifdef __APPLE__
return (bt_context_t*)&((ucontext64_t*)sigctx)->uc_mcontext64->__ss;
#elif defined(_CPU_ARM_)
// libunwind does not use `ucontext_t` on ARM.
// `unw_context_t` is a struct of 16 `unsigned long` which should
// have the same layout as the `arm_r0` to `arm_pc` fields in `sigcontext`
ucontext_t *ctx = (ucontext_t*)sigctx;
return (bt_context_t*)&ctx->uc_mcontext.arm_r0;
#else
return (bt_context_t*)sigctx;
#endif
}
static int thread0_exit_count = 0;
static void jl_exit_thread0(int signo, jl_bt_element_t *bt_data, size_t bt_size);
static inline __attribute__((unused)) uintptr_t jl_get_rsp_from_ctx(const void *_ctx)
{
#if defined(_OS_LINUX_) && defined(_CPU_X86_64_)
const ucontext_t *ctx = (const ucontext_t*)_ctx;
return ctx->uc_mcontext.gregs[REG_RSP];
#elif defined(_OS_LINUX_) && defined(_CPU_X86_)
const ucontext_t *ctx = (const ucontext_t*)_ctx;
return ctx->uc_mcontext.gregs[REG_ESP];
#elif defined(_OS_LINUX_) && defined(_CPU_AARCH64_)
const ucontext_t *ctx = (const ucontext_t*)_ctx;
return ctx->uc_mcontext.sp;
#elif defined(_OS_LINUX_) && defined(_CPU_ARM_)
const ucontext_t *ctx = (const ucontext_t*)_ctx;
return ctx->uc_mcontext.arm_sp;
#elif defined(_OS_DARWIN_) && defined(_CPU_X86_64_)
const ucontext64_t *ctx = (const ucontext64_t*)_ctx;
return ctx->uc_mcontext64->__ss.__rsp;
#elif defined(_OS_DARWIN_) && defined(_CPU_AARCH64_)
const ucontext64_t *ctx = (const ucontext64_t*)_ctx;
return ctx->uc_mcontext64->__ss.__sp;
#elif defined(_OS_FREEBSD_) && defined(_CPU_X86_64_)
const ucontext_t *ctx = (const ucontext_t*)_ctx;
return ctx->uc_mcontext.mc_rsp;
#elif defined(_OS_FREEBSD_) && defined(_CPU_AARCH64_)
const ucontext_t *ctx = (const ucontext_t*)_ctx;
return ctx->uc_mcontext.mc_gpregs.gp_sp;
#elif defined(_OS_OPENBSD_) && defined(_CPU_X86_64_)
const struct sigcontext *ctx = (const struct sigcontext *)_ctx;
return ctx->sc_rsp;
#else
// TODO Add support for PowerPC(64)?
return 0;
#endif
}
static int is_addr_on_sigstack(jl_ptls_t ptls, void *ptr)
{
// One guard page for signal_stack.
return ptls->signal_stack == NULL ||
((char*)ptr >= (char*)ptls->signal_stack - jl_page_size &&
(char*)ptr <= (char*)ptls->signal_stack + (ptls->signal_stack_size ? ptls->signal_stack_size : sig_stack_size));
}
// Modify signal context `_ctx` so that `fptr` will execute when the signal
// returns. `fptr` will execute on the signal stack, and must not return.
// jl_call_in_ctx is also currently executing on that signal stack,
// so be careful not to smash it
JL_NO_ASAN static void jl_call_in_ctx(jl_ptls_t ptls, void (*fptr)(void), int sig, void *_ctx)
{
// Modifying the ucontext should work but there is concern that
// sigreturn oriented programming mitigation can work against us
// by rejecting ucontext that is modified.
// The current (staged) implementation in the Linux Kernel only
// checks that the syscall is made in the signal handler and that
// the ucontext address is valid. Hopefully the value of the ucontext
// will not be part of the validation...
if (!ptls) {
sigset_t sset;
sigemptyset(&sset);
sigaddset(&sset, sig);
pthread_sigmask(SIG_UNBLOCK, &sset, NULL);
fptr();
return;
}
uintptr_t rsp = jl_get_rsp_from_ctx(_ctx);
if (is_addr_on_sigstack(ptls, (void*)rsp))
rsp = (rsp - 256) & ~(uintptr_t)15; // redzone and re-alignment
else
rsp = (uintptr_t)ptls->signal_stack + (ptls->signal_stack_size ? ptls->signal_stack_size : sig_stack_size);
assert(rsp % 16 == 0);
rsp -= 16;
#if defined(_OS_LINUX_) && defined(_CPU_X86_64_)
ucontext_t *ctx = (ucontext_t*)_ctx;
rsp -= sizeof(void*);
ctx->uc_mcontext.gregs[REG_RSP] = rsp;
ctx->uc_mcontext.gregs[REG_RIP] = (uintptr_t)fptr;
#elif defined(_OS_FREEBSD_) && defined(_CPU_X86_64_)
ucontext_t *ctx = (ucontext_t*)_ctx;
rsp -= sizeof(void*);
ctx->uc_mcontext.mc_rsp = rsp;
ctx->uc_mcontext.mc_rip = (uintptr_t)fptr;
#elif defined(_OS_LINUX_) && defined(_CPU_X86_)
ucontext_t *ctx = (ucontext_t*)_ctx;
rsp -= sizeof(void*);
ctx->uc_mcontext.gregs[REG_ESP] = rsp;
ctx->uc_mcontext.gregs[REG_EIP] = (uintptr_t)fptr;
#elif defined(_OS_FREEBSD_) && defined(_CPU_X86_)
ucontext_t *ctx = (ucontext_t*)_ctx;
rsp -= sizeof(void*);
ctx->uc_mcontext.mc_esp = rsp;
ctx->uc_mcontext.mc_eip = (uintptr_t)fptr;
#elif defined(_OS_OPENBSD_) && defined(_CPU_X86_64_)
struct sigcontext *ctx = (struct sigcontext *)_ctx;
rsp -= sizeof(void*);
ctx->sc_rsp = rsp;
ctx->sc_rip = fptr;
#elif defined(_OS_LINUX_) && defined(_CPU_AARCH64_)
ucontext_t *ctx = (ucontext_t*)_ctx;
ctx->uc_mcontext.sp = rsp;
ctx->uc_mcontext.regs[29] = 0; // Clear link register (x29)
ctx->uc_mcontext.pc = (uintptr_t)fptr;
#elif defined(_OS_FREEBSD_) && defined(_CPU_AARCH64_)
ucontext_t *ctx = (ucontext_t*)_ctx;
ctx->uc_mcontext.mc_gpregs.gp_sp = rsp;
ctx->uc_mcontext.mc_gpregs.gp_x[29] = 0; // Clear link register (x29)
ctx->uc_mcontext.mc_gpregs.gp_elr = (uintptr_t)fptr;
#elif defined(_OS_LINUX_) && defined(_CPU_ARM_)
ucontext_t *ctx = (ucontext_t*)_ctx;
uintptr_t target = (uintptr_t)fptr;
// Apparently some glibc's sigreturn target is running in thumb state.
// Mimic a `bx` instruction by setting the T(5) bit of CPSR
// depending on the target address.
uintptr_t cpsr = ctx->uc_mcontext.arm_cpsr;
// Thumb mode function pointer should have the lowest bit set
if (target & 1) {
target = target & ~((uintptr_t)1);
cpsr = cpsr | (1 << 5);
}
else {
cpsr = cpsr & ~(1 << 5);
}
ctx->uc_mcontext.arm_cpsr = cpsr;
ctx->uc_mcontext.arm_sp = rsp;
ctx->uc_mcontext.arm_lr = 0; // Clear link register
ctx->uc_mcontext.arm_pc = target;
#elif defined(_OS_DARWIN_) && (defined(_CPU_X86_64_) || defined(_CPU_AARCH64_))
// Only used for SIGFPE.
// This doesn't seems to be reliable when the SIGFPE is generated
// from a divide-by-zero exception, which is now handled by
// `catch_exception_raise`. It works fine when a signal is received
// due to `kill`/`raise` though.
ucontext64_t *ctx = (ucontext64_t*)_ctx;
#if defined(_CPU_X86_64_)
rsp -= sizeof(void*);
ctx->uc_mcontext64->__ss.__rsp = rsp;
ctx->uc_mcontext64->__ss.__rip = (uintptr_t)fptr;
#else
ctx->uc_mcontext64->__ss.__sp = rsp;
ctx->uc_mcontext64->__ss.__pc = (uintptr_t)fptr;
ctx->uc_mcontext64->__ss.__lr = 0;
#endif
#else
#pragma message("julia: throw-in-context not supported on this platform")
// TODO Add support for PowerPC(64)?
sigset_t sset;
sigemptyset(&sset);
sigaddset(&sset, sig);
pthread_sigmask(SIG_UNBLOCK, &sset, NULL);
fptr();
#endif
}
static void jl_throw_in_ctx(jl_task_t *ct, jl_value_t *e, int sig, void *sigctx)
{
jl_ptls_t ptls = ct->ptls;
if (!jl_get_safe_restore()) {
ptls->bt_size =
rec_backtrace_ctx(ptls->bt_data, JL_MAX_BT_SIZE, jl_to_bt_context(sigctx),
ct->gcstack);
ptls->sig_exception = e;
}
jl_call_in_ctx(ptls, &jl_sig_throw, sig, sigctx);
}
static pthread_t signals_thread;
static int is_addr_on_stack(jl_task_t *ct, void *addr)
{
if (ct->copy_stack) {
jl_ptls_t ptls = ct->ptls;
return ((char*)addr > (char*)ptls->stackbase - ptls->stacksize &&
(char*)addr < (char*)ptls->stackbase);
}
return ((char*)addr > (char*)ct->stkbuf &&
(char*)addr < (char*)ct->stkbuf + ct->bufsz);
}
static void sigdie_handler(int sig, siginfo_t *info, void *context)
{
signal(sig, SIG_DFL);
uv_tty_reset_mode();
if (sig == SIGILL)
jl_show_sigill(context);
jl_task_t *ct = jl_get_current_task();
jl_critical_error(sig, info->si_code, jl_to_bt_context(context), ct);
if (ct)
jl_atomic_store_relaxed(&ct->ptls->safepoint, (size_t*)NULL + 1);
if (info->si_code == 0 ||
info->si_code == SI_USER ||
#ifdef SI_KERNEL
info->si_code == SI_KERNEL ||
#endif
info->si_code == SI_QUEUE ||
#ifdef SI_MESGQ
info->si_code == SI_MESGQ ||
#endif
#ifdef SI_ASYNCIO
info->si_code == SI_ASYNCIO ||
#endif
#ifdef SI_SIGIO
info->si_code == SI_SIGIO ||
#endif
#ifdef SI_TKILL
info->si_code == SI_TKILL ||
#endif
info->si_code == SI_TIMER)
raise(sig);
else if (sig != SIGSEGV &&
sig != SIGBUS &&
sig != SIGILL &&
sig != SIGFPE &&
sig != SIGTRAP)
raise(sig);
// fall-through return to re-execute faulting statement (but without the
// error handler and the pgcstack having been destroyed)
}
#if defined(_CPU_X86_64_) || defined(_CPU_X86_)
enum x86_trap_flags {
USER_MODE = 0x4,
WRITE_FAULT = 0x2,
PAGE_PRESENT = 0x1 // whether this page is currently mapped into memory
};
int exc_reg_is_write_fault(uintptr_t err) {
return err & WRITE_FAULT;
}
#elif defined(_CPU_AARCH64_)
enum aarch64_esr_layout {
EC_MASK = ((uint32_t)0b111111) << 26,
EC_DATA_ABORT = ((uint32_t)0b100100) << 26,
DFSC_MASK = ((uint32_t)0b111111) << 0,
ISR_DA_WnR = ((uint32_t)1) << 6
};
int exc_reg_is_write_fault(uintptr_t esr) {
// n.b. we check that DFSC is either a permission fault (page in memory but not writable) or a translation fault (page not in memory)
// but because of info->si_code == SEGV_ACCERR, we know the kernel could have brought the page into memory.
// Access faults happen when trying to write to code or secure memory, which is a more severe violation, so we ignore those.
// AArch64 appears to leaves it up to a given implementer whether atomic update errors are reported as read or write faults.
return (esr & EC_MASK) == EC_DATA_ABORT &&
(((esr & DFSC_MASK) >= 0b000100 && // Translation flag fault, level 0.
(esr & DFSC_MASK) <= 0b000111) || // Translation fault, level 3.
((esr & DFSC_MASK) >= 0b001100 && // Permission flag fault, level 0.
(esr & DFSC_MASK) <= 0b001111)) && // Permission fault, level 3.
(esr & ISR_DA_WnR); // Attempted write
}
#endif
#if defined(HAVE_MACH)
#include "signals-mach.c"
#else
int jl_lock_stackwalk(void)
{
jl_lock_profile();
return 0;
}
void jl_unlock_stackwalk(int lockret)
{
(void)lockret;
jl_unlock_profile();
}
#if defined(_OS_LINUX_) && (defined(_CPU_X86_64_) || defined(_CPU_X86_))
int is_write_fault(void *context) {
ucontext_t *ctx = (ucontext_t*)context;
return exc_reg_is_write_fault(ctx->uc_mcontext.gregs[REG_ERR]);
}
#elif defined(_OS_LINUX_) && defined(_CPU_AARCH64_)
struct linux_aarch64_ctx_header {
uint32_t magic;
uint32_t size;
};
const uint32_t linux_esr_magic = 0x45535201;
int is_write_fault(void *context) {
ucontext_t *ctx = (ucontext_t*)context;
struct linux_aarch64_ctx_header *extra =
(struct linux_aarch64_ctx_header *)ctx->uc_mcontext.__reserved;
while (extra->magic != 0) {
if (extra->magic == linux_esr_magic) {
return exc_reg_is_write_fault(*(uint64_t*)&extra[1]);
}
extra = (struct linux_aarch64_ctx_header *)
(((uint8_t*)extra) + extra->size);
}
return 0;
}
#elif defined(_OS_FREEBSD_) && (defined(_CPU_X86_64_) || defined(_CPU_X86_))
int is_write_fault(void *context) {
ucontext_t *ctx = (ucontext_t*)context;
return exc_reg_is_write_fault(ctx->uc_mcontext.mc_err);
}
#elif defined(_OS_FREEBSD_) && defined(_CPU_AARCH64_)
// FreeBSD seems not to expose a means of accessing ESR via `ucontext_t` on AArch64.
// TODO: Is there an alternative approach that can be taken? ESR may become accessible
// in a future release though.
int is_write_fault(void *context) {
return 0;
}
#elif defined(_OS_OPENBSD_) && defined(_CPU_X86_64_)
int is_write_fault(void *context) {
struct sigcontext *ctx = (struct sigcontext *)context;
return exc_reg_is_write_fault(ctx->sc_err);
}
#else
#pragma message("Implement this query for consistent PROT_NONE handling")
int is_write_fault(void *context) {
return 0;
}
#endif
static int jl_is_on_sigstack(jl_ptls_t ptls, void *ptr, void *context)
{
return (ptls->signal_stack != NULL &&
is_addr_on_sigstack(ptls, ptr) &&
is_addr_on_sigstack(ptls, (void*)jl_get_rsp_from_ctx(context)));
}
JL_NO_ASAN static void segv_handler(int sig, siginfo_t *info, void *context)
{
assert(sig == SIGSEGV || sig == SIGBUS);
if (jl_get_safe_restore()) { // restarting jl_ or profile
jl_call_in_ctx(NULL, &jl_sig_throw, sig, context);
return;
}
jl_task_t *ct = jl_get_current_task();
if (ct == NULL || ct->ptls == NULL || jl_atomic_load_relaxed(&ct->ptls->gc_state) == JL_GC_STATE_WAITING) {
sigdie_handler(sig, info, context);
return;
}
if (sig == SIGSEGV && info->si_code == SEGV_ACCERR && jl_addr_is_safepoint((uintptr_t)info->si_addr) && !is_write_fault(context)) {
jl_set_gc_and_wait();
// Do not raise sigint on worker thread
if (jl_atomic_load_relaxed(&ct->tid) != 0)
return;
// n.b. if the user might have seen that we were in a state where it
// was safe to run GC concurrently, we might briefly enter a state
// where our execution is not consistent with the gc_state of this
// thread. That will quickly be rectified when we rerun the faulting
// instruction and end up right back here, or we start to run the
// exception handler and immediately hit the safepoint there.
if (ct->ptls->defer_signal) {
jl_safepoint_defer_sigint();
}
else if (jl_safepoint_consume_sigint()) {
jl_clear_force_sigint();
jl_throw_in_ctx(ct, jl_interrupt_exception, sig, context);
}
return;
}
if (ct->eh == NULL)
sigdie_handler(sig, info, context);
if ((sig != SIGBUS || info->si_code == BUS_ADRERR) && is_addr_on_stack(ct, info->si_addr)) { // stack overflow and not a BUS_ADRALN (alignment error)
stack_overflow_warning();
jl_throw_in_ctx(ct, jl_stackovf_exception, sig, context);
}
else if (jl_is_on_sigstack(ct->ptls, info->si_addr, context)) {
// This mainly happens when one of the finalizers during final cleanup
// on the signal stack has a deep/infinite recursion.
// There isn't anything more we can do
// (we are already corrupting that stack running this function)
// so just call `_exit` to terminate immediately.
jl_safe_printf("ERROR: Signal stack overflow, exit\n");
jl_raise(sig);
}
else if (sig == SIGSEGV && info->si_code == SEGV_ACCERR && is_write_fault(context)) { // writing to read-only memory (e.g., mmap)
jl_throw_in_ctx(ct, jl_readonlymemory_exception, sig, context);
}
else {
sigdie_handler(sig, info, context);
}
}
#if !defined(JL_DISABLE_LIBUNWIND)
static bt_context_t *signal_context;
pthread_mutex_t in_signal_lock;
static pthread_cond_t exit_signal_cond;
static pthread_cond_t signal_caught_cond;
int jl_thread_suspend_and_get_state(int tid, int timeout, bt_context_t *ctx)
{
struct timespec ts;
clock_gettime(CLOCK_REALTIME, &ts);
ts.tv_sec += timeout;
pthread_mutex_lock(&in_signal_lock);
jl_ptls_t ptls2 = jl_atomic_load_relaxed(&jl_all_tls_states)[tid];
jl_task_t *ct2 = ptls2 ? jl_atomic_load_relaxed(&ptls2->current_task) : NULL;
if (ct2 == NULL) {
// this thread is not alive or already dead
pthread_mutex_unlock(&in_signal_lock);
return 0;
}
jl_atomic_store_release(&ptls2->signal_request, 1);
pthread_kill(ptls2->system_id, SIGUSR2);
// wait for thread to acknowledge
int err = pthread_cond_timedwait(&signal_caught_cond, &in_signal_lock, &ts);
if (err == ETIMEDOUT) {
sig_atomic_t request = 1;
if (jl_atomic_cmpswap(&ptls2->signal_request, &request, 0)) {
pthread_mutex_unlock(&in_signal_lock);
return 0;
}
// Request is either now 0 (meaning the other thread is waiting for
// exit_signal_cond already),
// Or it is now -1 (meaning the other thread
// is waiting for in_signal_lock, and we need to release that lock
// here for a bit, until the other thread has a chance to get to the
// exit_signal_cond)
if (request == -1) {
err = pthread_cond_wait(&signal_caught_cond, &in_signal_lock);
assert(!err);
}
}
// Now the other thread is waiting on exit_signal_cond (verify that here by
// checking it is 0, and add an acquire barrier for good measure)
int request = jl_atomic_load_acquire(&ptls2->signal_request);
assert(request == 0); (void) request;
jl_atomic_store_release(&ptls2->signal_request, 1); // prepare to resume normally
*ctx = *signal_context;
return 1;
}
void jl_thread_resume(int tid)
{
jl_ptls_t ptls2 = jl_atomic_load_relaxed(&jl_all_tls_states)[tid];
pthread_cond_broadcast(&exit_signal_cond);
pthread_cond_wait(&signal_caught_cond, &in_signal_lock); // wait for thread to acknowledge (so that signal_request doesn't get mixed up)
// The other thread is waiting to leave exit_signal_cond (verify that here by
// checking it is 0, and add an acquire barrier for good measure)
int request = jl_atomic_load_acquire(&ptls2->signal_request);
assert(request == 0); (void) request;
pthread_mutex_unlock(&in_signal_lock);
}
#endif
// Throw jl_interrupt_exception if the master thread is in a signal async region
// or if SIGINT happens too often.
static void jl_try_deliver_sigint(void)
{
jl_ptls_t ptls2 = jl_atomic_load_relaxed(&jl_all_tls_states)[0];
jl_safepoint_enable_sigint();
jl_wake_libuv();
jl_atomic_store_release(&ptls2->signal_request, 2);
// This also makes sure `sleep` is aborted.
pthread_kill(ptls2->system_id, SIGUSR2);
}
// Write only by signal handling thread, read only by main thread
// no sync necessary.
static int thread0_exit_signo = 0;
static void JL_NORETURN jl_exit_thread0_cb(void)
{
CFI_NORETURN
jl_critical_error(thread0_exit_signo, 0, NULL, jl_current_task);
jl_atexit_hook(128);
jl_raise(thread0_exit_signo);
}
static void jl_exit_thread0(int signo, jl_bt_element_t *bt_data, size_t bt_size)
{
jl_ptls_t ptls2 = jl_atomic_load_relaxed(&jl_all_tls_states)[0];
bt_context_t signal_context;
// This also makes sure `sleep` is aborted.
if (jl_thread_suspend_and_get_state(0, 30, &signal_context)) {
thread0_exit_signo = signo;
ptls2->bt_size = bt_size; // <= JL_MAX_BT_SIZE
memcpy(ptls2->bt_data, bt_data, ptls2->bt_size * sizeof(bt_data[0]));
jl_atomic_store_release(&ptls2->signal_request, 3);
jl_thread_resume(0); // resume with message 3 (call jl_exit_thread0_cb)
}
else {
// thread 0 is gone? just do the exit ourself
jl_raise(signo);
}
}
// request:
// -1: beginning processing [invalid outside here]
// 0: nothing [not from here]
// 1: get state
// 2: throw sigint if `!defer_signal && io_wait` or if force throw threshold
// is reached
// 3: raise `thread0_exit_signo` and try to exit
void usr2_handler(int sig, siginfo_t *info, void *ctx)
{
jl_task_t *ct = jl_get_current_task();
if (ct == NULL)
return;
jl_ptls_t ptls = ct->ptls;
if (ptls == NULL)
return;
int errno_save = errno;
// acknowledge that we saw the signal_request
sig_atomic_t request = jl_atomic_exchange(&ptls->signal_request, -1);
#if !defined(JL_DISABLE_LIBUNWIND)
if (request == 1) {
pthread_mutex_lock(&in_signal_lock);
signal_context = jl_to_bt_context(ctx);
// acknowledge that we set the signal_caught_cond broadcast
request = jl_atomic_exchange(&ptls->signal_request, 0);
assert(request == -1); (void) request;
pthread_cond_broadcast(&signal_caught_cond);
pthread_cond_wait(&exit_signal_cond, &in_signal_lock);
request = jl_atomic_exchange(&ptls->signal_request, 0);
assert(request == 1 || request == 3);
// acknowledge that we got the resume signal
pthread_cond_broadcast(&signal_caught_cond);
pthread_mutex_unlock(&in_signal_lock);
}
else
#endif
jl_atomic_exchange(&ptls->signal_request, 0); // returns -1
if (request == 2) {
int force = jl_check_force_sigint();
if (force || (!ptls->defer_signal && ptls->io_wait)) {
jl_safepoint_consume_sigint();
if (force)
jl_safe_printf("WARNING: Force throwing a SIGINT\n");
// Force a throw
jl_clear_force_sigint();
jl_throw_in_ctx(ct, jl_interrupt_exception, sig, ctx);
}
}
else if (request == 3) {
jl_call_in_ctx(ct->ptls, jl_exit_thread0_cb, sig, ctx);
}
errno = errno_save;
}
// Because SIGUSR1 is dual-purpose, and the timer can have trailing signals after being deleted,
// a 2-second grace period is imposed to ignore any trailing timer-created signals so they don't get
// confused for user triggers
uint64_t last_timer_delete_time = 0;
int timer_graceperiod_elapsed(void)
{
return jl_hrtime() > (last_timer_delete_time + 2e9);
}
#if defined(HAVE_TIMER)
// Linux-style
#include <time.h>
#include <string.h> // for memset
static timer_t timerprof;
static struct itimerspec itsprof;
JL_DLLEXPORT int jl_profile_start_timer(void)
{
struct sigevent sigprof;
// Establish the signal event
memset(&sigprof, 0, sizeof(struct sigevent));
sigprof.sigev_notify = SIGEV_SIGNAL;
sigprof.sigev_signo = SIGUSR1;
sigprof.sigev_value.sival_ptr = &timerprof;
// Because SIGUSR1 is multipurpose, set `running` before so that we know that the first SIGUSR1 came from the timer
running = 1;
if (timer_create(CLOCK_REALTIME, &sigprof, &timerprof) == -1) {
running = 0;
return -2;
}
// Start the timer
itsprof.it_interval.tv_sec = 0;
itsprof.it_interval.tv_nsec = 0;
itsprof.it_value.tv_sec = nsecprof / GIGA;
itsprof.it_value.tv_nsec = nsecprof % GIGA;
if (timer_settime(timerprof, 0, &itsprof, NULL) == -1) {
running = 0;
return -3;
}
return 0;
}
JL_DLLEXPORT void jl_profile_stop_timer(void)
{
if (running) {
timer_delete(timerprof);
last_timer_delete_time = jl_hrtime();
running = 0;
}
}
#elif defined(__OpenBSD__)
JL_DLLEXPORT int jl_profile_start_timer(void)
{
return -1;
}
JL_DLLEXPORT void jl_profile_stop_timer(void)
{
}
#else
#error no profile tools available
#endif
#endif // HAVE_MACH
static void allocate_segv_handler(void)
{
struct sigaction act;
memset(&act, 0, sizeof(struct sigaction));
sigemptyset(&act.sa_mask);
act.sa_sigaction = segv_handler;
act.sa_flags = SA_ONSTACK | SA_SIGINFO;
if (sigaction(SIGSEGV, &act, NULL) < 0) {
jl_errorf("fatal error: sigaction: %s", strerror(errno));
}
// On AArch64, stack overflow triggers a SIGBUS
if (sigaction(SIGBUS, &act, NULL) < 0) {
jl_errorf("fatal error: sigaction: %s", strerror(errno));
}
}
void jl_install_thread_signal_handler(jl_ptls_t ptls)
{
#ifdef HAVE_MACH
attach_exception_port(pthread_mach_thread_np(ptls->system_id), 0);
#endif
stack_t ss;
if (sigaltstack(NULL, &ss) < 0)
jl_errorf("fatal error: sigaltstack: %s", strerror(errno));
if ((ss.ss_flags & SS_DISABLE) != SS_DISABLE)
return; // someone else appears to have already set this up, so just use that
size_t ssize = sig_stack_size;
void *signal_stack = jl_malloc_stack(&ssize, NULL);
ss.ss_flags = 0;
ss.ss_size = ssize;
assert(ssize != 0);
#ifndef _OS_OPENBSD_
/* fallback to malloc(), but it isn't possible on OpenBSD */
if (signal_stack == NULL) {
signal_stack = malloc(ssize);
ssize = 0;
if (signal_stack == NULL)
jl_safe_printf("\nwarning: julia signal alt stack could not be allocated (StackOverflowError will be fatal on this thread).\n");
else
jl_safe_printf("\nwarning: julia signal stack allocated without guard page (launch foreign threads earlier to avoid this warning).\n");
}
#endif
if (signal_stack != NULL) {
ss.ss_sp = signal_stack;
if (sigaltstack(&ss, NULL) < 0)
jl_errorf("fatal error: sigaltstack: %s", strerror(errno));
ptls->signal_stack = signal_stack;
ptls->signal_stack_size = ssize;
}
}
const static int sigwait_sigs[] = {
SIGINT, SIGTERM, SIGQUIT,
#ifdef SIGINFO
SIGINFO,
#else
SIGUSR1,
#endif
#if defined(HAVE_TIMER)
SIGUSR1,
#endif
0
};
static void jl_sigsetset(sigset_t *sset)
{
sigemptyset(sset);
for (const int *sig = sigwait_sigs; *sig; sig++)
sigaddset(sset, *sig);
}
#ifdef HAVE_KEVENT
static void kqueue_signal(int *sigqueue, struct kevent *ev, int sig)
{
if (*sigqueue == -1)
return;
EV_SET(ev, sig, EVFILT_SIGNAL, EV_ADD, 0, 0, 0);
if (kevent(*sigqueue, ev, 1, NULL, 0, NULL)) {
perror("signal kevent");
close(*sigqueue);
*sigqueue = -1;
}
else {
// kqueue gets signals before SIG_IGN, but does not remove them from pending (unlike sigwait)
signal(sig, SIG_IGN);
}
}
#endif
void trigger_profile_peek(void)
{
jl_safe_printf("\n======================================================================================\n");
jl_safe_printf("Information request received. A stacktrace will print followed by a %.1f second profile\n", profile_peek_duration);
jl_safe_printf("======================================================================================\n");
if (bt_size_max == 0){
// If the buffer hasn't been initialized, initialize with default size
// Keep these values synchronized with Profile.default_init()
if (jl_profile_init(10000000, 1000000) == -1) {
jl_safe_printf("ERROR: could not initialize the profile buffer");
return;
}
}
bt_size_cur = 0; // clear profile buffer
if (jl_profile_start_timer() < 0)
jl_safe_printf("ERROR: Could not start profile timer\n");
else
profile_autostop_time = jl_hrtime() + (profile_peek_duration * 1e9);
}
static void *signal_listener(void *arg)
{
static jl_bt_element_t bt_data[JL_MAX_BT_SIZE + 1];
static size_t bt_size = 0;
sigset_t sset;
int sig, critical, profile;
jl_sigsetset(&sset);
#if defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 199309L
siginfo_t info;
#endif
#ifdef HAVE_KEVENT
struct kevent ev;
int sigqueue = kqueue();
if (sigqueue == -1) {
perror("signal kqueue");
}
else {
for (const int *sig = sigwait_sigs; *sig; sig++)
kqueue_signal(&sigqueue, &ev, *sig);
if (sigqueue == -1) {
// re-enable sigwait for these
for (const int *sig = sigwait_sigs; *sig; sig++)
signal(*sig, SIG_DFL);
}
}
#endif
while (1) {
sig = 0;
errno = 0;
#ifdef HAVE_KEVENT
if (sigqueue != -1) {
int nevents = kevent(sigqueue, NULL, 0, &ev, 1, NULL);
if (nevents == -1) {
if (errno == EINTR)
continue;
perror("signal kevent");
}
if (nevents != 1) {
close(sigqueue);
sigqueue = -1;
for (const int *sig = sigwait_sigs; *sig; sig++)
signal(*sig, SIG_DFL);
continue;
}
sig = ev.ident;
}
else
#endif
#if defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 199309L
sig = sigwaitinfo(&sset, &info);
#else
if (sigwait(&sset, &sig))
sig = -1;
#endif
if (sig == -1) {
if (errno == EINTR)
continue;
sig = SIGABRT; // this branch can't occur, unless we had stack memory corruption of sset
}
profile = 0;
#ifndef HAVE_MACH
#if defined(HAVE_TIMER)
profile = (sig == SIGUSR1);
#if defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 199309L
if (profile && !(info.si_code == SI_TIMER &&
info.si_value.sival_ptr == &timerprof))
profile = 0;
#endif
#endif
#endif
if (sig == SIGINT) {
if (jl_ignore_sigint()) {
continue;
}
else if (exit_on_sigint) {
critical = 1;
}
else {
jl_try_deliver_sigint();
continue;
}
}
else {
critical = 0;
}
critical |= (sig == SIGTERM);
critical |= (sig == SIGABRT);
critical |= (sig == SIGQUIT);
#ifdef SIGINFO
critical |= (sig == SIGINFO);
#else
critical |= (sig == SIGUSR1 && !profile);
#endif
int doexit = critical;
#ifdef SIGINFO
if (sig == SIGINFO) {
if (running != 1)
trigger_profile_peek();
doexit = 0;
}
#else
if (sig == SIGUSR1) {
if (running != 1 && timer_graceperiod_elapsed())
trigger_profile_peek();
doexit = 0;
}
#endif
if (doexit) {
// The exit can get stuck if it happens at an unfortunate spot in thread 0
// (unavoidable due to its async nature).
// Try much harder to exit next time, if we get multiple exit requests.
// 1. unblock the signal, so this thread can be killed by it
// 2. reset the tty next, because we might die before we get another chance to do that
// 3. attempt a graceful cleanup of julia, followed by an abrupt end to the C runtime (except for fflush)
// 4. kill this thread with `raise`, to preserve the signo / exit code / and coredump configuration
// Similar to jl_raise, but a slightly different order of operations
sigset_t sset;
sigemptyset(&sset);
sigaddset(&sset, sig);
pthread_sigmask(SIG_UNBLOCK, &sset, NULL);
#ifdef HAVE_KEVENT
signal(sig, SIG_DFL);
#endif
uv_tty_reset_mode();
thread0_exit_count++;
fflush(NULL);
if (thread0_exit_count > 1) {
raise(sig); // very unlikely to return
_exit(128 + sig);
}
}
int nthreads = jl_atomic_load_acquire(&jl_n_threads);
bt_size = 0;
#if !defined(JL_DISABLE_LIBUNWIND)
bt_context_t signal_context;
// sample each thread, round-robin style in reverse order
// (so that thread zero gets notified last)
if (critical || profile) {
int lockret = jl_lock_stackwalk();
int *randperm;
if (profile)
randperm = profile_get_randperm(nthreads);
for (int idx = nthreads; idx-- > 0; ) {
// Stop the threads in the random or reverse round-robin order.
int i = profile ? randperm[idx] : idx;
// notify thread to stop
if (!jl_thread_suspend_and_get_state(i, 1, &signal_context))
continue;
// do backtrace on thread contexts for critical signals
// this part must be signal-handler safe
if (critical) {
bt_size += rec_backtrace_ctx(bt_data + bt_size,
JL_MAX_BT_SIZE / nthreads - 1,
&signal_context, NULL);
bt_data[bt_size++].uintptr = 0;
}
// do backtrace for profiler
if (profile && running) {
if (jl_profile_is_buffer_full()) {
// Buffer full: Delete the timer
jl_profile_stop_timer();
}
else {
// unwinding can fail, so keep track of the current state
// and restore from the SEGV handler if anything happens.
jl_jmp_buf *old_buf = jl_get_safe_restore();
jl_jmp_buf buf;
jl_set_safe_restore(&buf);
if (jl_setjmp(buf, 0)) {
jl_safe_printf("WARNING: profiler attempt to access an invalid memory location\n");
} else {
// Get backtrace data
bt_size_cur += rec_backtrace_ctx((jl_bt_element_t*)bt_data_prof + bt_size_cur,
bt_size_max - bt_size_cur - 1, &signal_context, NULL);
}
jl_set_safe_restore(old_buf);
jl_ptls_t ptls2 = jl_atomic_load_relaxed(&jl_all_tls_states)[i];
// META_OFFSET_THREADID store threadid but add 1 as 0 is preserved to indicate end of block
bt_data_prof[bt_size_cur++].uintptr = ptls2->tid + 1;
// META_OFFSET_TASKID store task id (never null)
bt_data_prof[bt_size_cur++].jlvalue = (jl_value_t*)jl_atomic_load_relaxed(&ptls2->current_task);
// META_OFFSET_CPUCYCLECLOCK store cpu cycle clock
bt_data_prof[bt_size_cur++].uintptr = cycleclock();
// META_OFFSET_SLEEPSTATE store whether thread is sleeping but add 1 as 0 is preserved to indicate end of block
bt_data_prof[bt_size_cur++].uintptr = jl_atomic_load_relaxed(&ptls2->sleep_check_state) + 1;
// Mark the end of this block with two 0's
bt_data_prof[bt_size_cur++].uintptr = 0;
bt_data_prof[bt_size_cur++].uintptr = 0;
}
}
// notify thread to resume
jl_thread_resume(i);
}
jl_unlock_stackwalk(lockret);
}
#ifndef HAVE_MACH
if (profile && running) {
jl_check_profile_autostop();
#if defined(HAVE_TIMER)
timer_settime(timerprof, 0, &itsprof, NULL);
#endif
}
#endif
#endif