view src/os/posix/vm/os_posix.cpp @ 5982:124fc080dc67

7112912: Message "Error occurred during initialization of VM" on boxes with lots of RAM Summary: Ergonomics now also takes available virtual memory into account when deciding for a heap size. The helper method to determine the maximum allocatable memory block now uses the appropriate OS specific calls to retrieve available virtual memory for the java process. In 32 bit environments this method now also searches for the maximum actually reservable amount of memory. Merge previously separate implementations for Linux/BSD/Solaris into a single method. Reviewed-by: jmasa, tamao
author tschatzl
date Tue, 18 Apr 2017 04:54:54 +0100
parents de5e8c8a9b87
children 72453885979f
line wrap: on
line source
/*
* Copyright (c) 1999, 2013, Oracle and/or its affiliates. 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.
*
*/

#include "utilities/globalDefinitions.hpp"
#include "prims/jvm.h"
#include "runtime/frame.inline.hpp"
#include "runtime/os.hpp"
#include "utilities/vmError.hpp"

#include <signal.h>
#include <unistd.h>
#include <sys/resource.h>
#include <sys/utsname.h>
#include <pthread.h>
#include <signal.h>

// Todo: provide a os::get_max_process_id() or similar. Number of processes
// may have been configured, can be read more accurately from proc fs etc.
#ifndef MAX_PID
#define MAX_PID INT_MAX
#endif
#define IS_VALID_PID(p) (p > 0 && p < MAX_PID)

// Check core dump limit and report possible place where core can be found
void os::check_or_create_dump(void* exceptionRecord, void* contextRecord, char* buffer, size_t bufferSize) {
  int n;
  struct rlimit rlim;
  bool success;

  n = get_core_path(buffer, bufferSize);

  if (getrlimit(RLIMIT_CORE, &rlim) != 0) {
    jio_snprintf(buffer + n, bufferSize - n, "/core or core.%d (may not exist)", current_process_id());
    success = true;
  } else {
    switch(rlim.rlim_cur) {
      case RLIM_INFINITY:
        jio_snprintf(buffer + n, bufferSize - n, "/core or core.%d", current_process_id());
        success = true;
        break;
      case 0:
        jio_snprintf(buffer, bufferSize, "Core dumps have been disabled. To enable core dumping, try \"ulimit -c unlimited\" before starting Java again");
        success = false;
        break;
      default:
        jio_snprintf(buffer + n, bufferSize - n, "/core or core.%d (max size %lu kB). To ensure a full core dump, try \"ulimit -c unlimited\" before starting Java again", current_process_id(), (unsigned long)(rlim.rlim_cur >> 10));
        success = true;
        break;
    }
  }
  VMError::report_coredump_status(buffer, success);
}

address os::get_caller_pc(int n) {
#ifdef _NMT_NOINLINE_
  n ++;
#endif
  frame fr = os::current_frame();
  while (n > 0 && fr.pc() &&
    !os::is_first_C_frame(&fr) && fr.sender_pc()) {
    fr = os::get_sender_for_C_frame(&fr);
    n --;
  }
  if (n == 0) {
    return fr.pc();
  } else {
    return NULL;
  }
}

int os::get_last_error() {
  return errno;
}

bool os::is_debugger_attached() {
  // not implemented
  return false;
}

void os::wait_for_keypress_at_exit(void) {
  // don't do anything on posix platforms
  return;
}

// Multiple threads can race in this code, and can remap over each other with MAP_FIXED,
// so on posix, unmap the section at the start and at the end of the chunk that we mapped
// rather than unmapping and remapping the whole chunk to get requested alignment.
char* os::reserve_memory_aligned(size_t size, size_t alignment) {
  assert((alignment & (os::vm_allocation_granularity() - 1)) == 0,
      "Alignment must be a multiple of allocation granularity (page size)");
  assert((size & (alignment -1)) == 0, "size must be 'alignment' aligned");

  size_t extra_size = size + alignment;
  assert(extra_size >= size, "overflow, size is too large to allow alignment");

  char* extra_base = os::reserve_memory(extra_size, NULL, alignment);

  if (extra_base == NULL) {
    return NULL;
  }

  // Do manual alignment
  char* aligned_base = (char*) align_size_up((uintptr_t) extra_base, alignment);

  // [  |                                       |  ]
  // ^ extra_base
  //    ^ extra_base + begin_offset == aligned_base
  //     extra_base + begin_offset + size       ^
  //                       extra_base + extra_size ^
  // |<>| == begin_offset
  //                              end_offset == |<>|
  size_t begin_offset = aligned_base - extra_base;
  size_t end_offset = (extra_base + extra_size) - (aligned_base + size);

  if (begin_offset > 0) {
      os::release_memory(extra_base, begin_offset);
  }

  if (end_offset > 0) {
      os::release_memory(extra_base + begin_offset + size, end_offset);
  }

  return aligned_base;
}

bool os::can_release_partial_region() {
  return true;
}

void os::Posix::print_load_average(outputStream* st) {
  st->print("load average:");
  double loadavg[3];
  os::loadavg(loadavg, 3);
  st->print("%0.02f %0.02f %0.02f", loadavg[0], loadavg[1], loadavg[2]);
  st->cr();
}

void os::Posix::print_rlimit_info(outputStream* st) {
  st->print("rlimit:");
  struct rlimit rlim;

  st->print(" STACK ");
  getrlimit(RLIMIT_STACK, &rlim);
  if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
  else st->print("%uk", rlim.rlim_cur >> 10);

  st->print(", CORE ");
  getrlimit(RLIMIT_CORE, &rlim);
  if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
  else st->print("%uk", rlim.rlim_cur >> 10);

  // Isn't there on solaris and aix.
#if !defined(TARGET_OS_FAMILY_solaris) && !defined(TARGET_OS_FAMILY_aix)
  st->print(", NPROC ");
  getrlimit(RLIMIT_NPROC, &rlim);
  if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
  else st->print("%d", rlim.rlim_cur);
#endif

  st->print(", NOFILE ");
  getrlimit(RLIMIT_NOFILE, &rlim);
  if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
  else st->print("%d", rlim.rlim_cur);

  st->print(", AS ");
  getrlimit(RLIMIT_AS, &rlim);
  if (rlim.rlim_cur == RLIM_INFINITY) st->print("infinity");
  else st->print("%uk", rlim.rlim_cur >> 10);
  st->cr();
}

void os::Posix::print_uname_info(outputStream* st) {
  // kernel
  st->print("uname:");
  struct utsname name;
  uname(&name);
  st->print(name.sysname); st->print(" ");
  st->print(name.release); st->print(" ");
  st->print(name.version); st->print(" ");
  st->print(name.machine);
  st->cr();
}

bool os::has_allocatable_memory_limit(julong* limit) {
  struct rlimit rlim;
  int getrlimit_res = getrlimit(RLIMIT_AS, &rlim);
  // if there was an error when calling getrlimit, assume that there is no limitation
  // on virtual memory.
  bool result;
  if ((getrlimit_res != 0) || (rlim.rlim_cur == RLIM_INFINITY)) {
    result = false;
  } else {
    *limit = (julong)rlim.rlim_cur;
    result = true;
  }
#ifdef _LP64
  return result;
#else
  // arbitrary virtual space limit for 32 bit Unices found by testing. If
  // getrlimit above returned a limit, bound it with this limit. Otherwise
  // directly use it.
  const julong max_virtual_limit = (julong)3800*M;
  if (result) {
    *limit = MIN2(*limit, max_virtual_limit);
  } else {
    *limit = max_virtual_limit;
  }

  // bound by actually allocatable memory. The algorithm uses two bounds, an
  // upper and a lower limit. The upper limit is the current highest amount of
  // memory that could not be allocated, the lower limit is the current highest
  // amount of memory that could be allocated.
  // The algorithm iteratively refines the result by halving the difference
  // between these limits, updating either the upper limit (if that value could
  // not be allocated) or the lower limit (if the that value could be allocated)
  // until the difference between these limits is "small".

  // the minimum amount of memory we care about allocating.
  const julong min_allocation_size = M;

  julong upper_limit = *limit;

  // first check a few trivial cases
  if (is_allocatable(upper_limit) || (upper_limit <= min_allocation_size)) {
    *limit = upper_limit;
  } else if (!is_allocatable(min_allocation_size)) {
    // we found that not even min_allocation_size is allocatable. Return it
    // anyway. There is no point to search for a better value any more.
    *limit = min_allocation_size;
  } else {
    // perform the binary search.
    julong lower_limit = min_allocation_size;
    while ((upper_limit - lower_limit) > min_allocation_size) {
      julong temp_limit = ((upper_limit - lower_limit) / 2) + lower_limit;
      temp_limit = align_size_down_(temp_limit, min_allocation_size);
      if (is_allocatable(temp_limit)) {
        lower_limit = temp_limit;
      } else {
        upper_limit = temp_limit;
      }
    }
    *limit = lower_limit;
  }
  return true;
#endif
}

// Returned string is a constant. For unknown signals "UNKNOWN" is returned.
const char* os::Posix::get_signal_name(int sig, char* out, size_t outlen) {

  static const struct {
    int sig; const char* name;
  }
  info[] =
  {
    {  SIGABRT,     "SIGABRT" },
#ifdef SIGAIO
    {  SIGAIO,      "SIGAIO" },
#endif
    {  SIGALRM,     "SIGALRM" },
#ifdef SIGALRM1
    {  SIGALRM1,    "SIGALRM1" },
#endif
    {  SIGBUS,      "SIGBUS" },
#ifdef SIGCANCEL
    {  SIGCANCEL,   "SIGCANCEL" },
#endif
    {  SIGCHLD,     "SIGCHLD" },
#ifdef SIGCLD
    {  SIGCLD,      "SIGCLD" },
#endif
    {  SIGCONT,     "SIGCONT" },
#ifdef SIGCPUFAIL
    {  SIGCPUFAIL,  "SIGCPUFAIL" },
#endif
#ifdef SIGDANGER
    {  SIGDANGER,   "SIGDANGER" },
#endif
#ifdef SIGDIL
    {  SIGDIL,      "SIGDIL" },
#endif
#ifdef SIGEMT
    {  SIGEMT,      "SIGEMT" },
#endif
    {  SIGFPE,      "SIGFPE" },
#ifdef SIGFREEZE
    {  SIGFREEZE,   "SIGFREEZE" },
#endif
#ifdef SIGGFAULT
    {  SIGGFAULT,   "SIGGFAULT" },
#endif
#ifdef SIGGRANT
    {  SIGGRANT,    "SIGGRANT" },
#endif
    {  SIGHUP,      "SIGHUP" },
    {  SIGILL,      "SIGILL" },
    {  SIGINT,      "SIGINT" },
#ifdef SIGIO
    {  SIGIO,       "SIGIO" },
#endif
#ifdef SIGIOINT
    {  SIGIOINT,    "SIGIOINT" },
#endif
#ifdef SIGIOT
  // SIGIOT is there for BSD compatibility, but on most Unices just a
  // synonym for SIGABRT. The result should be "SIGABRT", not
  // "SIGIOT".
  #if (SIGIOT != SIGABRT )
    {  SIGIOT,      "SIGIOT" },
  #endif
#endif
#ifdef SIGKAP
    {  SIGKAP,      "SIGKAP" },
#endif
    {  SIGKILL,     "SIGKILL" },
#ifdef SIGLOST
    {  SIGLOST,     "SIGLOST" },
#endif
#ifdef SIGLWP
    {  SIGLWP,      "SIGLWP" },
#endif
#ifdef SIGLWPTIMER
    {  SIGLWPTIMER, "SIGLWPTIMER" },
#endif
#ifdef SIGMIGRATE
    {  SIGMIGRATE,  "SIGMIGRATE" },
#endif
#ifdef SIGMSG
    {  SIGMSG,      "SIGMSG" },
#endif
    {  SIGPIPE,     "SIGPIPE" },
#ifdef SIGPOLL
    {  SIGPOLL,     "SIGPOLL" },
#endif
#ifdef SIGPRE
    {  SIGPRE,      "SIGPRE" },
#endif
    {  SIGPROF,     "SIGPROF" },
#ifdef SIGPTY
    {  SIGPTY,      "SIGPTY" },
#endif
#ifdef SIGPWR
    {  SIGPWR,      "SIGPWR" },
#endif
    {  SIGQUIT,     "SIGQUIT" },
#ifdef SIGRECONFIG
    {  SIGRECONFIG, "SIGRECONFIG" },
#endif
#ifdef SIGRECOVERY
    {  SIGRECOVERY, "SIGRECOVERY" },
#endif
#ifdef SIGRESERVE
    {  SIGRESERVE,  "SIGRESERVE" },
#endif
#ifdef SIGRETRACT
    {  SIGRETRACT,  "SIGRETRACT" },
#endif
#ifdef SIGSAK
    {  SIGSAK,      "SIGSAK" },
#endif
    {  SIGSEGV,     "SIGSEGV" },
#ifdef SIGSOUND
    {  SIGSOUND,    "SIGSOUND" },
#endif
    {  SIGSTOP,     "SIGSTOP" },
    {  SIGSYS,      "SIGSYS" },
#ifdef SIGSYSERROR
    {  SIGSYSERROR, "SIGSYSERROR" },
#endif
#ifdef SIGTALRM
    {  SIGTALRM,    "SIGTALRM" },
#endif
    {  SIGTERM,     "SIGTERM" },
#ifdef SIGTHAW
    {  SIGTHAW,     "SIGTHAW" },
#endif
    {  SIGTRAP,     "SIGTRAP" },
#ifdef SIGTSTP
    {  SIGTSTP,     "SIGTSTP" },
#endif
    {  SIGTTIN,     "SIGTTIN" },
    {  SIGTTOU,     "SIGTTOU" },
#ifdef SIGURG
    {  SIGURG,      "SIGURG" },
#endif
    {  SIGUSR1,     "SIGUSR1" },
    {  SIGUSR2,     "SIGUSR2" },
#ifdef SIGVIRT
    {  SIGVIRT,     "SIGVIRT" },
#endif
    {  SIGVTALRM,   "SIGVTALRM" },
#ifdef SIGWAITING
    {  SIGWAITING,  "SIGWAITING" },
#endif
#ifdef SIGWINCH
    {  SIGWINCH,    "SIGWINCH" },
#endif
#ifdef SIGWINDOW
    {  SIGWINDOW,   "SIGWINDOW" },
#endif
    {  SIGXCPU,     "SIGXCPU" },
    {  SIGXFSZ,     "SIGXFSZ" },
#ifdef SIGXRES
    {  SIGXRES,     "SIGXRES" },
#endif
    { -1, NULL }
  };

  const char* ret = NULL;

#ifdef SIGRTMIN
  if (sig >= SIGRTMIN && sig <= SIGRTMAX) {
    if (sig == SIGRTMIN) {
      ret = "SIGRTMIN";
    } else if (sig == SIGRTMAX) {
      ret = "SIGRTMAX";
    } else {
      jio_snprintf(out, outlen, "SIGRTMIN+%d", sig - SIGRTMIN);
      return out;
    }
  }
#endif

  if (sig > 0) {
    for (int idx = 0; info[idx].sig != -1; idx ++) {
      if (info[idx].sig == sig) {
        ret = info[idx].name;
        break;
      }
    }
  }

  if (!ret) {
    if (!is_valid_signal(sig)) {
      ret = "INVALID";
    } else {
      ret = "UNKNOWN";
    }
  }

  jio_snprintf(out, outlen, ret);
  return out;
}

// Returns true if signal number is valid.
bool os::Posix::is_valid_signal(int sig) {
  // MacOS not really POSIX compliant: sigaddset does not return
  // an error for invalid signal numbers. However, MacOS does not
  // support real time signals and simply seems to have just 33
  // signals with no holes in the signal range.
#ifdef __APPLE__
  return sig >= 1 && sig < NSIG;
#else
  // Use sigaddset to check for signal validity.
  sigset_t set;
  if (sigaddset(&set, sig) == -1 && errno == EINVAL) {
    return false;
  }
  return true;
#endif
}

#define NUM_IMPORTANT_SIGS 32
// Returns one-line short description of a signal set in a user provided buffer.
const char* os::Posix::describe_signal_set_short(const sigset_t* set, char* buffer, size_t buf_size) {
  assert(buf_size == (NUM_IMPORTANT_SIGS + 1), "wrong buffer size");
  // Note: for shortness, just print out the first 32. That should
  // cover most of the useful ones, apart from realtime signals.
  for (int sig = 1; sig <= NUM_IMPORTANT_SIGS; sig++) {
    const int rc = sigismember(set, sig);
    if (rc == -1 && errno == EINVAL) {
      buffer[sig-1] = '?';
    } else {
      buffer[sig-1] = rc == 0 ? '0' : '1';
    }
  }
  buffer[NUM_IMPORTANT_SIGS] = 0;
  return buffer;
}

// Prints one-line description of a signal set.
void os::Posix::print_signal_set_short(outputStream* st, const sigset_t* set) {
  char buf[NUM_IMPORTANT_SIGS + 1];
  os::Posix::describe_signal_set_short(set, buf, sizeof(buf));
  st->print(buf);
}

// Writes one-line description of a combination of sigaction.sa_flags into a user
// provided buffer. Returns that buffer.
const char* os::Posix::describe_sa_flags(int flags, char* buffer, size_t size) {
  char* p = buffer;
  size_t remaining = size;
  bool first = true;
  int idx = 0;

  assert(buffer, "invalid argument");

  if (size == 0) {
    return buffer;
  }

  strncpy(buffer, "none", size);

  const struct {
    int i;
    const char* s;
  } flaginfo [] = {
    { SA_NOCLDSTOP, "SA_NOCLDSTOP" },
    { SA_ONSTACK,   "SA_ONSTACK"   },
    { SA_RESETHAND, "SA_RESETHAND" },
    { SA_RESTART,   "SA_RESTART"   },
    { SA_SIGINFO,   "SA_SIGINFO"   },
    { SA_NOCLDWAIT, "SA_NOCLDWAIT" },
    { SA_NODEFER,   "SA_NODEFER"   },
#ifdef AIX
    { SA_ONSTACK,   "SA_ONSTACK"   },
    { SA_OLDSTYLE,  "SA_OLDSTYLE"  },
#endif
    { 0, NULL }
  };

  for (idx = 0; flaginfo[idx].s && remaining > 1; idx++) {
    if (flags & flaginfo[idx].i) {
      if (first) {
        jio_snprintf(p, remaining, "%s", flaginfo[idx].s);
        first = false;
      } else {
        jio_snprintf(p, remaining, "|%s", flaginfo[idx].s);
      }
      const size_t len = strlen(p);
      p += len;
      remaining -= len;
    }
  }

  buffer[size - 1] = '\0';

  return buffer;
}

// Prints one-line description of a combination of sigaction.sa_flags.
void os::Posix::print_sa_flags(outputStream* st, int flags) {
  char buffer[0x100];
  os::Posix::describe_sa_flags(flags, buffer, sizeof(buffer));
  st->print(buffer);
}

// Helper function for os::Posix::print_siginfo_...():
// return a textual description for signal code.
struct enum_sigcode_desc_t {
  const char* s_name;
  const char* s_desc;
};

static bool get_signal_code_description(const siginfo_t* si, enum_sigcode_desc_t* out) {

  const struct {
    int sig; int code; const char* s_code; const char* s_desc;
  } t1 [] = {
    { SIGILL,  ILL_ILLOPC,   "ILL_ILLOPC",   "Illegal opcode." },
    { SIGILL,  ILL_ILLOPN,   "ILL_ILLOPN",   "Illegal operand." },
    { SIGILL,  ILL_ILLADR,   "ILL_ILLADR",   "Illegal addressing mode." },
    { SIGILL,  ILL_ILLTRP,   "ILL_ILLTRP",   "Illegal trap." },
    { SIGILL,  ILL_PRVOPC,   "ILL_PRVOPC",   "Privileged opcode." },
    { SIGILL,  ILL_PRVREG,   "ILL_PRVREG",   "Privileged register." },
    { SIGILL,  ILL_COPROC,   "ILL_COPROC",   "Coprocessor error." },
    { SIGILL,  ILL_BADSTK,   "ILL_BADSTK",   "Internal stack error." },
#if defined(IA64) && defined(LINUX)
    { SIGILL,  ILL_BADIADDR, "ILL_BADIADDR", "Unimplemented instruction address" },
    { SIGILL,  ILL_BREAK,    "ILL_BREAK",    "Application Break instruction" },
#endif
    { SIGFPE,  FPE_INTDIV,   "FPE_INTDIV",   "Integer divide by zero." },
    { SIGFPE,  FPE_INTOVF,   "FPE_INTOVF",   "Integer overflow." },
    { SIGFPE,  FPE_FLTDIV,   "FPE_FLTDIV",   "Floating-point divide by zero." },
    { SIGFPE,  FPE_FLTOVF,   "FPE_FLTOVF",   "Floating-point overflow." },
    { SIGFPE,  FPE_FLTUND,   "FPE_FLTUND",   "Floating-point underflow." },
    { SIGFPE,  FPE_FLTRES,   "FPE_FLTRES",   "Floating-point inexact result." },
    { SIGFPE,  FPE_FLTINV,   "FPE_FLTINV",   "Invalid floating-point operation." },
    { SIGFPE,  FPE_FLTSUB,   "FPE_FLTSUB",   "Subscript out of range." },
    { SIGSEGV, SEGV_MAPERR,  "SEGV_MAPERR",  "Address not mapped to object." },
    { SIGSEGV, SEGV_ACCERR,  "SEGV_ACCERR",  "Invalid permissions for mapped object." },
#ifdef AIX
    // no explanation found what keyerr would be
    { SIGSEGV, SEGV_KEYERR,  "SEGV_KEYERR",  "key error" },
#endif
#if defined(IA64) && !defined(AIX)
    { SIGSEGV, SEGV_PSTKOVF, "SEGV_PSTKOVF", "Paragraph stack overflow" },
#endif
    { SIGBUS,  BUS_ADRALN,   "BUS_ADRALN",   "Invalid address alignment." },
    { SIGBUS,  BUS_ADRERR,   "BUS_ADRERR",   "Nonexistent physical address." },
    { SIGBUS,  BUS_OBJERR,   "BUS_OBJERR",   "Object-specific hardware error." },
    { SIGTRAP, TRAP_BRKPT,   "TRAP_BRKPT",   "Process breakpoint." },
    { SIGTRAP, TRAP_TRACE,   "TRAP_TRACE",   "Process trace trap." },
    { SIGCHLD, CLD_EXITED,   "CLD_EXITED",   "Child has exited." },
    { SIGCHLD, CLD_KILLED,   "CLD_KILLED",   "Child has terminated abnormally and did not create a core file." },
    { SIGCHLD, CLD_DUMPED,   "CLD_DUMPED",   "Child has terminated abnormally and created a core file." },
    { SIGCHLD, CLD_TRAPPED,  "CLD_TRAPPED",  "Traced child has trapped." },
    { SIGCHLD, CLD_STOPPED,  "CLD_STOPPED",  "Child has stopped." },
    { SIGCHLD, CLD_CONTINUED,"CLD_CONTINUED","Stopped child has continued." },
#ifdef SIGPOLL
    { SIGPOLL, POLL_OUT,     "POLL_OUT",     "Output buffers available." },
    { SIGPOLL, POLL_MSG,     "POLL_MSG",     "Input message available." },
    { SIGPOLL, POLL_ERR,     "POLL_ERR",     "I/O error." },
    { SIGPOLL, POLL_PRI,     "POLL_PRI",     "High priority input available." },
    { SIGPOLL, POLL_HUP,     "POLL_HUP",     "Device disconnected. [Option End]" },
#endif
    { -1, -1, NULL, NULL }
  };

  // Codes valid in any signal context.
  const struct {
    int code; const char* s_code; const char* s_desc;
  } t2 [] = {
    { SI_USER,      "SI_USER",     "Signal sent by kill()." },
    { SI_QUEUE,     "SI_QUEUE",    "Signal sent by the sigqueue()." },
    { SI_TIMER,     "SI_TIMER",    "Signal generated by expiration of a timer set by timer_settime()." },
    { SI_ASYNCIO,   "SI_ASYNCIO",  "Signal generated by completion of an asynchronous I/O request." },
    { SI_MESGQ,     "SI_MESGQ",    "Signal generated by arrival of a message on an empty message queue." },
    // Linux specific
#ifdef SI_TKILL
    { SI_TKILL,     "SI_TKILL",    "Signal sent by tkill (pthread_kill)" },
#endif
#ifdef SI_DETHREAD
    { SI_DETHREAD,  "SI_DETHREAD", "Signal sent by execve() killing subsidiary threads" },
#endif
#ifdef SI_KERNEL
    { SI_KERNEL,    "SI_KERNEL",   "Signal sent by kernel." },
#endif
#ifdef SI_SIGIO
    { SI_SIGIO,     "SI_SIGIO",    "Signal sent by queued SIGIO" },
#endif

#ifdef AIX
    { SI_UNDEFINED, "SI_UNDEFINED","siginfo contains partial information" },
    { SI_EMPTY,     "SI_EMPTY",    "siginfo contains no useful information" },
#endif

#ifdef __sun
    { SI_NOINFO,    "SI_NOINFO",   "No signal information" },
    { SI_RCTL,      "SI_RCTL",     "kernel generated signal via rctl action" },
    { SI_LWP,       "SI_LWP",      "Signal sent via lwp_kill" },
#endif

    { -1, NULL, NULL }
  };

  const char* s_code = NULL;
  const char* s_desc = NULL;

  for (int i = 0; t1[i].sig != -1; i ++) {
    if (t1[i].sig == si->si_signo && t1[i].code == si->si_code) {
      s_code = t1[i].s_code;
      s_desc = t1[i].s_desc;
      break;
    }
  }

  if (s_code == NULL) {
    for (int i = 0; t2[i].s_code != NULL; i ++) {
      if (t2[i].code == si->si_code) {
        s_code = t2[i].s_code;
        s_desc = t2[i].s_desc;
      }
    }
  }

  if (s_code == NULL) {
    out->s_name = "unknown";
    out->s_desc = "unknown";
    return false;
  }

  out->s_name = s_code;
  out->s_desc = s_desc;

  return true;
}

// A POSIX conform, platform-independend siginfo print routine.
// Short print out on one line.
void os::Posix::print_siginfo_brief(outputStream* os, const siginfo_t* si) {
  char buf[20];
  os->print("siginfo: ");

  if (!si) {
    os->print("<null>");
    return;
  }

  // See print_siginfo_full() for details.
  const int sig = si->si_signo;

  os->print("si_signo: %d (%s)", sig, os::Posix::get_signal_name(sig, buf, sizeof(buf)));

  enum_sigcode_desc_t ed;
  if (get_signal_code_description(si, &ed)) {
    os->print(", si_code: %d (%s)", si->si_code, ed.s_name);
  } else {
    os->print(", si_code: %d (unknown)", si->si_code);
  }

  if (si->si_errno) {
    os->print(", si_errno: %d", si->si_errno);
  }

  const int me = (int) ::getpid();
  const int pid = (int) si->si_pid;

  if (si->si_code == SI_USER || si->si_code == SI_QUEUE) {
    if (IS_VALID_PID(pid) && pid != me) {
      os->print(", sent from pid: %d (uid: %d)", pid, (int) si->si_uid);
    }
  } else if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
             sig == SIGTRAP || sig == SIGFPE) {
    os->print(", si_addr: " PTR_FORMAT, si->si_addr);
#ifdef SIGPOLL
  } else if (sig == SIGPOLL) {
    os->print(", si_band: " PTR64_FORMAT, (uint64_t)si->si_band);
#endif
  } else if (sig == SIGCHLD) {
    os->print_cr(", si_pid: %d, si_uid: %d, si_status: %d", (int) si->si_pid, si->si_uid, si->si_status);
  }
}

os::WatcherThreadCrashProtection::WatcherThreadCrashProtection() {
  assert(Thread::current()->is_Watcher_thread(), "Must be WatcherThread");
}

/*
 * See the caveats for this class in os_posix.hpp
 * Protects the callback call so that SIGSEGV / SIGBUS jumps back into this
 * method and returns false. If none of the signals are raised, returns true.
 * The callback is supposed to provide the method that should be protected.
 */
bool os::WatcherThreadCrashProtection::call(os::CrashProtectionCallback& cb) {
  sigset_t saved_sig_mask;

  assert(Thread::current()->is_Watcher_thread(), "Only for WatcherThread");
  assert(!WatcherThread::watcher_thread()->has_crash_protection(),
      "crash_protection already set?");

  // we cannot rely on sigsetjmp/siglongjmp to save/restore the signal mask
  // since on at least some systems (OS X) siglongjmp will restore the mask
  // for the process, not the thread
  pthread_sigmask(0, NULL, &saved_sig_mask);
  if (sigsetjmp(_jmpbuf, 0) == 0) {
    // make sure we can see in the signal handler that we have crash protection
    // installed
    WatcherThread::watcher_thread()->set_crash_protection(this);
    cb.call();
    // and clear the crash protection
    WatcherThread::watcher_thread()->set_crash_protection(NULL);
    return true;
  }
  // this happens when we siglongjmp() back
  pthread_sigmask(SIG_SETMASK, &saved_sig_mask, NULL);
  WatcherThread::watcher_thread()->set_crash_protection(NULL);
  return false;
}

void os::WatcherThreadCrashProtection::restore() {
  assert(WatcherThread::watcher_thread()->has_crash_protection(),
      "must have crash protection");

  siglongjmp(_jmpbuf, 1);
}

void os::WatcherThreadCrashProtection::check_crash_protection(int sig,
    Thread* thread) {

  if (thread != NULL &&
      thread->is_Watcher_thread() &&
      WatcherThread::watcher_thread()->has_crash_protection()) {

    if (sig == SIGSEGV || sig == SIGBUS) {
      WatcherThread::watcher_thread()->crash_protection()->restore();
    }
  }
}