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os_linux.cpp
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os_linux.cpp
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/*
* Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2015, 2022 SAP SE. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
// no precompiled headers
#include "classfile/vmSymbols.hpp"
#include "code/icBuffer.hpp"
#include "code/vtableStubs.hpp"
#include "compiler/compileBroker.hpp"
#include "compiler/disassembler.hpp"
#include "hugepages.hpp"
#include "interpreter/interpreter.hpp"
#include "jvm.h"
#include "jvmtifiles/jvmti.h"
#include "logging/log.hpp"
#include "logging/logStream.hpp"
#include "memory/allocation.inline.hpp"
#include "oops/oop.inline.hpp"
#include "os_linux.inline.hpp"
#include "os_posix.inline.hpp"
#include "osContainer_linux.hpp"
#include "prims/jniFastGetField.hpp"
#include "prims/jvm_misc.hpp"
#include "runtime/arguments.hpp"
#include "runtime/atomic.hpp"
#include "runtime/globals.hpp"
#include "runtime/globals_extension.hpp"
#include "runtime/init.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/javaCalls.hpp"
#include "runtime/javaThread.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/objectMonitor.hpp"
#include "runtime/osInfo.hpp"
#include "runtime/osThread.hpp"
#include "runtime/perfMemory.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/statSampler.hpp"
#include "runtime/stubRoutines.hpp"
#include "runtime/threadCritical.hpp"
#include "runtime/threads.hpp"
#include "runtime/threadSMR.hpp"
#include "runtime/timer.hpp"
#include "runtime/vm_version.hpp"
#include "signals_posix.hpp"
#include "semaphore_posix.hpp"
#include "services/memTracker.hpp"
#include "services/runtimeService.hpp"
#include "utilities/align.hpp"
#include "utilities/checkedCast.hpp"
#include "utilities/debug.hpp"
#include "utilities/decoder.hpp"
#include "utilities/defaultStream.hpp"
#include "utilities/events.hpp"
#include "utilities/elfFile.hpp"
#include "utilities/growableArray.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/macros.hpp"
#include "utilities/powerOfTwo.hpp"
#include "utilities/vmError.hpp"
#if INCLUDE_JFR
#include "jfr/jfrEvents.hpp"
#endif
// put OS-includes here
# include <sys/types.h>
# include <sys/mman.h>
# include <sys/stat.h>
# include <sys/select.h>
# include <sys/sendfile.h>
# include <pthread.h>
# include <signal.h>
# include <endian.h>
# include <errno.h>
# include <dlfcn.h>
# include <stdio.h>
# include <unistd.h>
# include <sys/resource.h>
# include <pthread.h>
# include <sys/stat.h>
# include <sys/time.h>
# include <sys/times.h>
# include <sys/utsname.h>
# include <sys/socket.h>
# include <pwd.h>
# include <poll.h>
# include <fcntl.h>
# include <string.h>
# include <syscall.h>
# include <sys/sysinfo.h>
# include <sys/ipc.h>
# include <sys/shm.h>
# include <link.h>
# include <stdint.h>
# include <inttypes.h>
# include <sys/ioctl.h>
# include <linux/elf-em.h>
# include <sys/prctl.h>
#ifdef __GLIBC__
# include <malloc.h>
#endif
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#include <sched.h>
#undef _GNU_SOURCE
#else
#include <sched.h>
#endif
// if RUSAGE_THREAD for getrusage() has not been defined, do it here. The code calling
// getrusage() is prepared to handle the associated failure.
#ifndef RUSAGE_THREAD
#define RUSAGE_THREAD (1) /* only the calling thread */
#endif
#define MAX_PATH (2 * K)
#define MAX_SECS 100000000
// for timer info max values which include all bits
#define ALL_64_BITS CONST64(0xFFFFFFFFFFFFFFFF)
#ifdef MUSL_LIBC
// dlvsym is not a part of POSIX
// and musl libc doesn't implement it.
static void *dlvsym(void *handle,
const char *symbol,
const char *version) {
// load the latest version of symbol
return dlsym(handle, symbol);
}
#endif
enum CoredumpFilterBit {
FILE_BACKED_PVT_BIT = 1 << 2,
FILE_BACKED_SHARED_BIT = 1 << 3,
LARGEPAGES_BIT = 1 << 6,
DAX_SHARED_BIT = 1 << 8
};
////////////////////////////////////////////////////////////////////////////////
// global variables
julong os::Linux::_physical_memory = 0;
address os::Linux::_initial_thread_stack_bottom = nullptr;
uintptr_t os::Linux::_initial_thread_stack_size = 0;
int (*os::Linux::_pthread_getcpuclockid)(pthread_t, clockid_t *) = nullptr;
int (*os::Linux::_pthread_setname_np)(pthread_t, const char*) = nullptr;
pthread_t os::Linux::_main_thread;
bool os::Linux::_supports_fast_thread_cpu_time = false;
const char * os::Linux::_libc_version = nullptr;
const char * os::Linux::_libpthread_version = nullptr;
#ifdef __GLIBC__
// We want to be buildable and runnable on older and newer glibcs, so resolve both
// mallinfo and mallinfo2 dynamically.
struct old_mallinfo {
int arena;
int ordblks;
int smblks;
int hblks;
int hblkhd;
int usmblks;
int fsmblks;
int uordblks;
int fordblks;
int keepcost;
};
typedef struct old_mallinfo (*mallinfo_func_t)(void);
static mallinfo_func_t g_mallinfo = nullptr;
struct new_mallinfo {
size_t arena;
size_t ordblks;
size_t smblks;
size_t hblks;
size_t hblkhd;
size_t usmblks;
size_t fsmblks;
size_t uordblks;
size_t fordblks;
size_t keepcost;
};
typedef struct new_mallinfo (*mallinfo2_func_t)(void);
static mallinfo2_func_t g_mallinfo2 = nullptr;
typedef int (*malloc_info_func_t)(int options, FILE *stream);
static malloc_info_func_t g_malloc_info = nullptr;
#endif // __GLIBC__
static int clock_tics_per_sec = 100;
// If the VM might have been created on the primordial thread, we need to resolve the
// primordial thread stack bounds and check if the current thread might be the
// primordial thread in places. If we know that the primordial thread is never used,
// such as when the VM was created by one of the standard java launchers, we can
// avoid this
static bool suppress_primordial_thread_resolution = false;
// utility functions
julong os::Linux::available_memory_in_container() {
julong avail_mem = static_cast<julong>(-1L);
if (OSContainer::is_containerized()) {
jlong mem_limit = OSContainer::memory_limit_in_bytes();
jlong mem_usage;
if (mem_limit > 0 && (mem_usage = OSContainer::memory_usage_in_bytes()) < 1) {
log_debug(os, container)("container memory usage failed: " JLONG_FORMAT ", using host value", mem_usage);
}
if (mem_limit > 0 && mem_usage > 0) {
avail_mem = mem_limit > mem_usage ? (julong)mem_limit - (julong)mem_usage : 0;
}
}
return avail_mem;
}
julong os::available_memory() {
return Linux::available_memory();
}
julong os::Linux::available_memory() {
julong avail_mem = available_memory_in_container();
if (avail_mem != static_cast<julong>(-1L)) {
log_trace(os)("available container memory: " JULONG_FORMAT, avail_mem);
return avail_mem;
}
FILE *fp = os::fopen("/proc/meminfo", "r");
if (fp != nullptr) {
char buf[80];
do {
if (fscanf(fp, "MemAvailable: " JULONG_FORMAT " kB", &avail_mem) == 1) {
avail_mem *= K;
break;
}
} while (fgets(buf, sizeof(buf), fp) != nullptr);
fclose(fp);
}
if (avail_mem == static_cast<julong>(-1L)) {
avail_mem = free_memory();
}
log_trace(os)("available memory: " JULONG_FORMAT, avail_mem);
return avail_mem;
}
julong os::free_memory() {
return Linux::free_memory();
}
julong os::Linux::free_memory() {
// values in struct sysinfo are "unsigned long"
struct sysinfo si;
julong free_mem = available_memory_in_container();
if (free_mem != static_cast<julong>(-1L)) {
log_trace(os)("free container memory: " JULONG_FORMAT, free_mem);
return free_mem;
}
sysinfo(&si);
free_mem = (julong)si.freeram * si.mem_unit;
log_trace(os)("free memory: " JULONG_FORMAT, free_mem);
return free_mem;
}
julong os::physical_memory() {
jlong phys_mem = 0;
if (OSContainer::is_containerized()) {
jlong mem_limit;
if ((mem_limit = OSContainer::memory_limit_in_bytes()) > 0) {
log_trace(os)("total container memory: " JLONG_FORMAT, mem_limit);
return mem_limit;
}
}
phys_mem = Linux::physical_memory();
log_trace(os)("total system memory: " JLONG_FORMAT, phys_mem);
return phys_mem;
}
static uint64_t initial_total_ticks = 0;
static uint64_t initial_steal_ticks = 0;
static bool has_initial_tick_info = false;
static void next_line(FILE *f) {
int c;
do {
c = fgetc(f);
} while (c != '\n' && c != EOF);
}
bool os::Linux::get_tick_information(CPUPerfTicks* pticks, int which_logical_cpu) {
FILE* fh;
uint64_t userTicks, niceTicks, systemTicks, idleTicks;
// since at least kernel 2.6 : iowait: time waiting for I/O to complete
// irq: time servicing interrupts; softirq: time servicing softirqs
uint64_t iowTicks = 0, irqTicks = 0, sirqTicks= 0;
// steal (since kernel 2.6.11): time spent in other OS when running in a virtualized environment
uint64_t stealTicks = 0;
// guest (since kernel 2.6.24): time spent running a virtual CPU for guest OS under the
// control of the Linux kernel
uint64_t guestNiceTicks = 0;
int logical_cpu = -1;
const int required_tickinfo_count = (which_logical_cpu == -1) ? 4 : 5;
int n;
memset(pticks, 0, sizeof(CPUPerfTicks));
if ((fh = os::fopen("/proc/stat", "r")) == nullptr) {
return false;
}
if (which_logical_cpu == -1) {
n = fscanf(fh, "cpu " UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " "
UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " "
UINT64_FORMAT " " UINT64_FORMAT " ",
&userTicks, &niceTicks, &systemTicks, &idleTicks,
&iowTicks, &irqTicks, &sirqTicks,
&stealTicks, &guestNiceTicks);
} else {
// Move to next line
next_line(fh);
// find the line for requested cpu faster to just iterate linefeeds?
for (int i = 0; i < which_logical_cpu; i++) {
next_line(fh);
}
n = fscanf(fh, "cpu%u " UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " "
UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " " UINT64_FORMAT " "
UINT64_FORMAT " " UINT64_FORMAT " ",
&logical_cpu, &userTicks, &niceTicks,
&systemTicks, &idleTicks, &iowTicks, &irqTicks, &sirqTicks,
&stealTicks, &guestNiceTicks);
}
fclose(fh);
if (n < required_tickinfo_count || logical_cpu != which_logical_cpu) {
return false;
}
pticks->used = userTicks + niceTicks;
pticks->usedKernel = systemTicks + irqTicks + sirqTicks;
pticks->total = userTicks + niceTicks + systemTicks + idleTicks +
iowTicks + irqTicks + sirqTicks + stealTicks + guestNiceTicks;
if (n > required_tickinfo_count + 3) {
pticks->steal = stealTicks;
pticks->has_steal_ticks = true;
} else {
pticks->steal = 0;
pticks->has_steal_ticks = false;
}
return true;
}
#ifndef SYS_gettid
// i386: 224, ia64: 1105, amd64: 186, sparc: 143
#ifdef __ia64__
#define SYS_gettid 1105
#else
#ifdef __i386__
#define SYS_gettid 224
#else
#ifdef __amd64__
#define SYS_gettid 186
#else
#ifdef __sparc__
#define SYS_gettid 143
#else
#error define gettid for the arch
#endif
#endif
#endif
#endif
#endif
// pid_t gettid()
//
// Returns the kernel thread id of the currently running thread. Kernel
// thread id is used to access /proc.
pid_t os::Linux::gettid() {
long rslt = syscall(SYS_gettid);
assert(rslt != -1, "must be."); // old linuxthreads implementation?
return (pid_t)rslt;
}
// Returns the amount of swap currently configured, in bytes.
// This can change at any time.
julong os::Linux::host_swap() {
struct sysinfo si;
sysinfo(&si);
return (julong)si.totalswap;
}
// Most versions of linux have a bug where the number of processors are
// determined by looking at the /proc file system. In a chroot environment,
// the system call returns 1.
static bool unsafe_chroot_detected = false;
static const char *unstable_chroot_error = "/proc file system not found.\n"
"Java may be unstable running multithreaded in a chroot "
"environment on Linux when /proc filesystem is not mounted.";
void os::Linux::initialize_system_info() {
set_processor_count((int)sysconf(_SC_NPROCESSORS_CONF));
if (processor_count() == 1) {
pid_t pid = os::Linux::gettid();
char fname[32];
jio_snprintf(fname, sizeof(fname), "/proc/%d", pid);
FILE *fp = os::fopen(fname, "r");
if (fp == nullptr) {
unsafe_chroot_detected = true;
} else {
fclose(fp);
}
}
_physical_memory = (julong)sysconf(_SC_PHYS_PAGES) * (julong)sysconf(_SC_PAGESIZE);
assert(processor_count() > 0, "linux error");
}
void os::init_system_properties_values() {
// The next steps are taken in the product version:
//
// Obtain the JAVA_HOME value from the location of libjvm.so.
// This library should be located at:
// <JAVA_HOME>/lib/{client|server}/libjvm.so.
//
// If "/jre/lib/" appears at the right place in the path, then we
// assume libjvm.so is installed in a JDK and we use this path.
//
// Otherwise exit with message: "Could not create the Java virtual machine."
//
// The following extra steps are taken in the debugging version:
//
// If "/jre/lib/" does NOT appear at the right place in the path
// instead of exit check for $JAVA_HOME environment variable.
//
// If it is defined and we are able to locate $JAVA_HOME/jre/lib/<arch>,
// then we append a fake suffix "hotspot/libjvm.so" to this path so
// it looks like libjvm.so is installed there
// <JAVA_HOME>/jre/lib/<arch>/hotspot/libjvm.so.
//
// Otherwise exit.
//
// Important note: if the location of libjvm.so changes this
// code needs to be changed accordingly.
// See ld(1):
// The linker uses the following search paths to locate required
// shared libraries:
// 1: ...
// ...
// 7: The default directories, normally /lib and /usr/lib.
#ifndef OVERRIDE_LIBPATH
#if defined(_LP64)
#define DEFAULT_LIBPATH "/usr/lib64:/lib64:/lib:/usr/lib"
#else
#define DEFAULT_LIBPATH "/lib:/usr/lib"
#endif
#else
#define DEFAULT_LIBPATH OVERRIDE_LIBPATH
#endif
// Base path of extensions installed on the system.
#define SYS_EXT_DIR "/usr/java/packages"
#define EXTENSIONS_DIR "/lib/ext"
// Buffer that fits several snprintfs.
// Note that the space for the colon and the trailing null are provided
// by the nulls included by the sizeof operator.
const size_t bufsize =
MAX2((size_t)MAXPATHLEN, // For dll_dir & friends.
(size_t)MAXPATHLEN + sizeof(EXTENSIONS_DIR) + sizeof(SYS_EXT_DIR) + sizeof(EXTENSIONS_DIR)); // extensions dir
char *buf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
// sysclasspath, java_home, dll_dir
{
char *pslash;
os::jvm_path(buf, bufsize);
// Found the full path to libjvm.so.
// Now cut the path to <java_home>/jre if we can.
pslash = strrchr(buf, '/');
if (pslash != nullptr) {
*pslash = '\0'; // Get rid of /libjvm.so.
}
pslash = strrchr(buf, '/');
if (pslash != nullptr) {
*pslash = '\0'; // Get rid of /{client|server|hotspot}.
}
Arguments::set_dll_dir(buf);
if (pslash != nullptr) {
pslash = strrchr(buf, '/');
if (pslash != nullptr) {
*pslash = '\0'; // Get rid of /lib.
}
}
Arguments::set_java_home(buf);
if (!set_boot_path('/', ':')) {
vm_exit_during_initialization("Failed setting boot class path.", nullptr);
}
}
// Where to look for native libraries.
//
// Note: Due to a legacy implementation, most of the library path
// is set in the launcher. This was to accommodate linking restrictions
// on legacy Linux implementations (which are no longer supported).
// Eventually, all the library path setting will be done here.
//
// However, to prevent the proliferation of improperly built native
// libraries, the new path component /usr/java/packages is added here.
// Eventually, all the library path setting will be done here.
{
// Get the user setting of LD_LIBRARY_PATH, and prepended it. It
// should always exist (until the legacy problem cited above is
// addressed).
const char *v = ::getenv("LD_LIBRARY_PATH");
const char *v_colon = ":";
if (v == nullptr) { v = ""; v_colon = ""; }
// That's +1 for the colon and +1 for the trailing '\0'.
size_t pathsize = strlen(v) + 1 + sizeof(SYS_EXT_DIR) + sizeof("/lib/") + sizeof(DEFAULT_LIBPATH) + 1;
char *ld_library_path = NEW_C_HEAP_ARRAY(char, pathsize, mtInternal);
os::snprintf_checked(ld_library_path, pathsize, "%s%s" SYS_EXT_DIR "/lib:" DEFAULT_LIBPATH, v, v_colon);
Arguments::set_library_path(ld_library_path);
FREE_C_HEAP_ARRAY(char, ld_library_path);
}
// Extensions directories.
os::snprintf_checked(buf, bufsize, "%s" EXTENSIONS_DIR ":" SYS_EXT_DIR EXTENSIONS_DIR, Arguments::get_java_home());
Arguments::set_ext_dirs(buf);
FREE_C_HEAP_ARRAY(char, buf);
#undef DEFAULT_LIBPATH
#undef SYS_EXT_DIR
#undef EXTENSIONS_DIR
}
////////////////////////////////////////////////////////////////////////////////
// breakpoint support
void os::breakpoint() {
BREAKPOINT;
}
extern "C" void breakpoint() {
// use debugger to set breakpoint here
}
//////////////////////////////////////////////////////////////////////////////
// detecting pthread library
void os::Linux::libpthread_init() {
// Save glibc and pthread version strings.
#if !defined(_CS_GNU_LIBC_VERSION) || \
!defined(_CS_GNU_LIBPTHREAD_VERSION)
#error "glibc too old (< 2.3.2)"
#endif
#ifdef MUSL_LIBC
// confstr() from musl libc returns EINVAL for
// _CS_GNU_LIBC_VERSION and _CS_GNU_LIBPTHREAD_VERSION
os::Linux::set_libc_version("musl - unknown");
os::Linux::set_libpthread_version("musl - unknown");
#else
size_t n = confstr(_CS_GNU_LIBC_VERSION, nullptr, 0);
assert(n > 0, "cannot retrieve glibc version");
char *str = (char *)malloc(n, mtInternal);
confstr(_CS_GNU_LIBC_VERSION, str, n);
os::Linux::set_libc_version(str);
n = confstr(_CS_GNU_LIBPTHREAD_VERSION, nullptr, 0);
assert(n > 0, "cannot retrieve pthread version");
str = (char *)malloc(n, mtInternal);
confstr(_CS_GNU_LIBPTHREAD_VERSION, str, n);
os::Linux::set_libpthread_version(str);
#endif
}
/////////////////////////////////////////////////////////////////////////////
// thread stack expansion
// os::Linux::manually_expand_stack() takes care of expanding the thread
// stack. Note that this is normally not needed: pthread stacks allocate
// thread stack using mmap() without MAP_NORESERVE, so the stack is already
// committed. Therefore it is not necessary to expand the stack manually.
//
// Manually expanding the stack was historically needed on LinuxThreads
// thread stacks, which were allocated with mmap(MAP_GROWSDOWN). Nowadays
// it is kept to deal with very rare corner cases:
//
// For one, user may run the VM on an own implementation of threads
// whose stacks are - like the old LinuxThreads - implemented using
// mmap(MAP_GROWSDOWN).
//
// Also, this coding may be needed if the VM is running on the primordial
// thread. Normally we avoid running on the primordial thread; however,
// user may still invoke the VM on the primordial thread.
//
// The following historical comment describes the details about running
// on a thread stack allocated with mmap(MAP_GROWSDOWN):
// Force Linux kernel to expand current thread stack. If "bottom" is close
// to the stack guard, caller should block all signals.
//
// MAP_GROWSDOWN:
// A special mmap() flag that is used to implement thread stacks. It tells
// kernel that the memory region should extend downwards when needed. This
// allows early versions of LinuxThreads to only mmap the first few pages
// when creating a new thread. Linux kernel will automatically expand thread
// stack as needed (on page faults).
//
// However, because the memory region of a MAP_GROWSDOWN stack can grow on
// demand, if a page fault happens outside an already mapped MAP_GROWSDOWN
// region, it's hard to tell if the fault is due to a legitimate stack
// access or because of reading/writing non-exist memory (e.g. buffer
// overrun). As a rule, if the fault happens below current stack pointer,
// Linux kernel does not expand stack, instead a SIGSEGV is sent to the
// application (see Linux kernel fault.c).
//
// This Linux feature can cause SIGSEGV when VM bangs thread stack for
// stack overflow detection.
//
// Newer version of LinuxThreads (since glibc-2.2, or, RH-7.x) and NPTL do
// not use MAP_GROWSDOWN.
//
// To get around the problem and allow stack banging on Linux, we need to
// manually expand thread stack after receiving the SIGSEGV.
//
// There are two ways to expand thread stack to address "bottom", we used
// both of them in JVM before 1.5:
// 1. adjust stack pointer first so that it is below "bottom", and then
// touch "bottom"
// 2. mmap() the page in question
//
// Now alternate signal stack is gone, it's harder to use 2. For instance,
// if current sp is already near the lower end of page 101, and we need to
// call mmap() to map page 100, it is possible that part of the mmap() frame
// will be placed in page 100. When page 100 is mapped, it is zero-filled.
// That will destroy the mmap() frame and cause VM to crash.
//
// The following code works by adjusting sp first, then accessing the "bottom"
// page to force a page fault. Linux kernel will then automatically expand the
// stack mapping.
//
// _expand_stack_to() assumes its frame size is less than page size, which
// should always be true if the function is not inlined.
static void NOINLINE _expand_stack_to(address bottom) {
address sp;
size_t size;
volatile char *p;
// Adjust bottom to point to the largest address within the same page, it
// gives us a one-page buffer if alloca() allocates slightly more memory.
bottom = (address)align_down((uintptr_t)bottom, os::vm_page_size());
bottom += os::vm_page_size() - 1;
// sp might be slightly above current stack pointer; if that's the case, we
// will alloca() a little more space than necessary, which is OK. Don't use
// os::current_stack_pointer(), as its result can be slightly below current
// stack pointer, causing us to not alloca enough to reach "bottom".
sp = (address)&sp;
if (sp > bottom) {
size = sp - bottom;
p = (volatile char *)alloca(size);
assert(p != nullptr && p <= (volatile char *)bottom, "alloca problem?");
p[0] = '\0';
}
}
void os::Linux::expand_stack_to(address bottom) {
_expand_stack_to(bottom);
}
bool os::Linux::manually_expand_stack(JavaThread * t, address addr) {
assert(t!=nullptr, "just checking");
assert(t->osthread()->expanding_stack(), "expand should be set");
if (t->is_in_usable_stack(addr)) {
sigset_t mask_all, old_sigset;
sigfillset(&mask_all);
pthread_sigmask(SIG_SETMASK, &mask_all, &old_sigset);
_expand_stack_to(addr);
pthread_sigmask(SIG_SETMASK, &old_sigset, nullptr);
return true;
}
return false;
}
//////////////////////////////////////////////////////////////////////////////
// create new thread
// Thread start routine for all newly created threads
static void *thread_native_entry(Thread *thread) {
thread->record_stack_base_and_size();
#ifndef __GLIBC__
// Try to randomize the cache line index of hot stack frames.
// This helps when threads of the same stack traces evict each other's
// cache lines. The threads can be either from the same JVM instance, or
// from different JVM instances. The benefit is especially true for
// processors with hyperthreading technology.
// This code is not needed anymore in glibc because it has MULTI_PAGE_ALIASING
// and we did not see any degradation in performance without `alloca()`.
static int counter = 0;
int pid = os::current_process_id();
int random = ((pid ^ counter++) & 7) * 128;
void *stackmem = alloca(random != 0 ? random : 1); // ensure we allocate > 0
// Ensure the alloca result is used in a way that prevents the compiler from eliding it.
*(char *)stackmem = 1;
#endif
thread->initialize_thread_current();
OSThread* osthread = thread->osthread();
Monitor* sync = osthread->startThread_lock();
osthread->set_thread_id(checked_cast<OSThread::thread_id_t>(os::current_thread_id()));
if (UseNUMA) {
int lgrp_id = os::numa_get_group_id();
if (lgrp_id != -1) {
thread->set_lgrp_id(lgrp_id);
}
}
// initialize signal mask for this thread
PosixSignals::hotspot_sigmask(thread);
// initialize floating point control register
os::Linux::init_thread_fpu_state();
// handshaking with parent thread
{
MutexLocker ml(sync, Mutex::_no_safepoint_check_flag);
// notify parent thread
osthread->set_state(INITIALIZED);
sync->notify_all();
// wait until os::start_thread()
while (osthread->get_state() == INITIALIZED) {
sync->wait_without_safepoint_check();
}
}
log_info(os, thread)("Thread is alive (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
os::current_thread_id(), (uintx) pthread_self());
assert(osthread->pthread_id() != 0, "pthread_id was not set as expected");
if (DelayThreadStartALot) {
os::naked_short_sleep(100);
}
// call one more level start routine
thread->call_run();
// Note: at this point the thread object may already have deleted itself.
// Prevent dereferencing it from here on out.
thread = nullptr;
log_info(os, thread)("Thread finished (tid: " UINTX_FORMAT ", pthread id: " UINTX_FORMAT ").",
os::current_thread_id(), (uintx) pthread_self());
return 0;
}
// On Linux, glibc places static TLS blocks (for __thread variables) on
// the thread stack. This decreases the stack size actually available
// to threads.
//
// For large static TLS sizes, this may cause threads to malfunction due
// to insufficient stack space. This is a well-known issue in glibc:
// http://sourceware.org/bugzilla/show_bug.cgi?id=11787.
//
// As a workaround, we call a private but assumed-stable glibc function,
// __pthread_get_minstack() to obtain the minstack size and derive the
// static TLS size from it. We then increase the user requested stack
// size by this TLS size. The same function is used to determine whether
// adjustStackSizeForGuardPages() needs to be true.
//
// Due to compatibility concerns, this size adjustment is opt-in and
// controlled via AdjustStackSizeForTLS.
typedef size_t (*GetMinStack)(const pthread_attr_t *attr);
GetMinStack _get_minstack_func = nullptr; // Initialized via os::init_2()
// Returns the size of the static TLS area glibc puts on thread stacks.
// The value is cached on first use, which occurs when the first thread
// is created during VM initialization.
static size_t get_static_tls_area_size(const pthread_attr_t *attr) {
size_t tls_size = 0;
if (_get_minstack_func != nullptr) {
// Obtain the pthread minstack size by calling __pthread_get_minstack.
size_t minstack_size = _get_minstack_func(attr);
// Remove non-TLS area size included in minstack size returned
// by __pthread_get_minstack() to get the static TLS size.
// If adjustStackSizeForGuardPages() is true, minstack size includes
// guard_size. Otherwise guard_size is automatically added
// to the stack size by pthread_create and is no longer included
// in minstack size. In both cases, the guard_size is taken into
// account, so there is no need to adjust the result for that.
//
// Although __pthread_get_minstack() is a private glibc function,
// it is expected to have a stable behavior across future glibc
// versions while glibc still allocates the static TLS blocks off
// the stack. Following is glibc 2.28 __pthread_get_minstack():
//
// size_t
// __pthread_get_minstack (const pthread_attr_t *attr)
// {
// return GLRO(dl_pagesize) + __static_tls_size + PTHREAD_STACK_MIN;
// }
//
//
// The following 'minstack_size > os::vm_page_size() + PTHREAD_STACK_MIN'
// if check is done for precaution.
if (minstack_size > os::vm_page_size() + PTHREAD_STACK_MIN) {
tls_size = minstack_size - os::vm_page_size() - PTHREAD_STACK_MIN;
}
}
log_info(os, thread)("Stack size adjustment for TLS is " SIZE_FORMAT,
tls_size);
return tls_size;
}
// In glibc versions prior to 2.27 the guard size mechanism
// was not implemented properly. The POSIX standard requires adding
// the size of the guard pages to the stack size, instead glibc
// took the space out of 'stacksize'. Thus we need to adapt the requested
// stack_size by the size of the guard pages to mimic proper behaviour.
// The fix in glibc 2.27 has now been backported to numerous earlier
// glibc versions so we need to do a dynamic runtime check.
static bool _adjustStackSizeForGuardPages = true;
bool os::Linux::adjustStackSizeForGuardPages() {
return _adjustStackSizeForGuardPages;
}
#ifdef __GLIBC__
static void init_adjust_stacksize_for_guard_pages() {
assert(_get_minstack_func == nullptr, "initialization error");
_get_minstack_func =(GetMinStack)dlsym(RTLD_DEFAULT, "__pthread_get_minstack");
log_info(os, thread)("Lookup of __pthread_get_minstack %s",
_get_minstack_func == nullptr ? "failed" : "succeeded");
if (_get_minstack_func != nullptr) {
pthread_attr_t attr;
pthread_attr_init(&attr);
size_t min_stack = _get_minstack_func(&attr);
size_t guard = 16 * K; // Actual value doesn't matter as it is not examined
pthread_attr_setguardsize(&attr, guard);
size_t min_stack2 = _get_minstack_func(&attr);
pthread_attr_destroy(&attr);
// If the minimum stack size changed when we added the guard page space
// then we need to perform the adjustment.
_adjustStackSizeForGuardPages = (min_stack2 != min_stack);
log_info(os)("Glibc stack size guard page adjustment is %sneeded",
_adjustStackSizeForGuardPages ? "" : "not ");
}
}
#endif // GLIBC
bool os::create_thread(Thread* thread, ThreadType thr_type,
size_t req_stack_size) {
assert(thread->osthread() == nullptr, "caller responsible");
// Allocate the OSThread object
OSThread* osthread = new (std::nothrow) OSThread();
if (osthread == nullptr) {
return false;
}
// set the correct thread state
osthread->set_thread_type(thr_type);
// Initial state is ALLOCATED but not INITIALIZED
osthread->set_state(ALLOCATED);
thread->set_osthread(osthread);
// init thread attributes
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
// Calculate stack size if it's not specified by caller.
size_t stack_size = os::Posix::get_initial_stack_size(thr_type, req_stack_size);
size_t guard_size = os::Linux::default_guard_size(thr_type);
// Configure glibc guard page. Must happen before calling
// get_static_tls_area_size(), which uses the guard_size.
pthread_attr_setguardsize(&attr, guard_size);
// Apply stack size adjustments if needed. However, be careful not to end up
// with a size of zero due to overflow. Don't add the adjustment in that case.
size_t stack_adjust_size = 0;
if (AdjustStackSizeForTLS) {
// Adjust the stack_size for on-stack TLS - see get_static_tls_area_size().
stack_adjust_size += get_static_tls_area_size(&attr);
} else if (os::Linux::adjustStackSizeForGuardPages()) {
stack_adjust_size += guard_size;
}
stack_adjust_size = align_up(stack_adjust_size, os::vm_page_size());
if (stack_size <= SIZE_MAX - stack_adjust_size) {
stack_size += stack_adjust_size;
}
assert(is_aligned(stack_size, os::vm_page_size()), "stack_size not aligned");
if (THPStackMitigation) {
// In addition to the glibc guard page that prevents inter-thread-stack hugepage
// coalescing (see comment in os::Linux::default_guard_size()), we also make
// sure the stack size itself is not huge-page-size aligned; that makes it much
// more likely for thread stack boundaries to be unaligned as well and hence
// protects thread stacks from being targeted by khugepaged.
if (HugePages::thp_pagesize() > 0 &&
is_aligned(stack_size, HugePages::thp_pagesize())) {
stack_size += os::vm_page_size();
}
}
int status = pthread_attr_setstacksize(&attr, stack_size);
if (status != 0) {
// pthread_attr_setstacksize() function can fail
// if the stack size exceeds a system-imposed limit.
assert_status(status == EINVAL, status, "pthread_attr_setstacksize");
log_warning(os, thread)("The %sthread stack size specified is invalid: " SIZE_FORMAT "k",
(thr_type == compiler_thread) ? "compiler " : ((thr_type == java_thread) ? "" : "VM "),
stack_size / K);
thread->set_osthread(nullptr);
delete osthread;
return false;
}
ThreadState state;
{
ResourceMark rm;
pthread_t tid;
int ret = 0;
int limit = 3;
do {
ret = pthread_create(&tid, &attr, (void* (*)(void*)) thread_native_entry, thread);
} while (ret == EAGAIN && limit-- > 0);
char buf[64];
if (ret == 0) {
log_info(os, thread)("Thread \"%s\" started (pthread id: " UINTX_FORMAT ", attributes: %s). ",
thread->name(), (uintx) tid, os::Posix::describe_pthread_attr(buf, sizeof(buf), &attr));
// Print current timer slack if override is enabled and timer slack value is available.
// Avoid calling prctl otherwise for extra safety.
if (TimerSlack >= 0) {
int slack = prctl(PR_GET_TIMERSLACK);
if (slack >= 0) {
log_info(os, thread)("Thread \"%s\" (pthread id: " UINTX_FORMAT ") timer slack: %dns",
thread->name(), (uintx) tid, slack);
}
}
} else {
log_warning(os, thread)("Failed to start thread \"%s\" - pthread_create failed (%s) for attributes: %s.",
thread->name(), os::errno_name(ret), os::Posix::describe_pthread_attr(buf, sizeof(buf), &attr));
// Log some OS information which might explain why creating the thread failed.
log_info(os, thread)("Number of threads approx. running in the VM: %d", Threads::number_of_threads());
LogStream st(Log(os, thread)::info());
os::Posix::print_rlimit_info(&st);
os::print_memory_info(&st);
os::Linux::print_proc_sys_info(&st);