Attention AIX developers - factoring out POSIX signal code (JDK-8252324)

Thu Aug 27 20:30:40 UTC 2020

Hi Gerard,

> I don’t want to straight break AIX port unexpectedly.
Thanks for that! We highly appreciate that you take care of it.

It’s not surprising that adapting the AIX code is difficult.

I’ve added Thomas to Cc. He’s surely the most experienced person for these AIX specific things.
Unfortunately, he’s currently very busy because he’s contributing his new metaspace implementation.

We have to discuss how we can help.

Best regards,
Martin

From: gerard ziemski <gerard.ziemski at oracle.com>
Sent: Donnerstag, 27. August 2020 19:19
To: hotspot-runtime-dev at openjdk.java.net
Cc: Schmidt, Lutz <lutz.schmidt at sap.com>; Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; Doerr, Martin <martin.doerr at sap.com>
Subject: Attention AIX developers - factoring out POSIX signal code (JDK-8252324)

hi all,

I’m hoping I have included the right people in this email, but everyone is welcome to provide feedback.

I have a code for JDK-8252324, which factors out the common POSIX signal related code out into common file, so that all platforms can benefit from fixes that apply to all POSIX platforms (like JDK-82514380)

The preliminary webrev can be found here: http://cr.openjdk.java.net/~gziemski/8252324_pre1

I tried to port the changes to AIX myself, but got bogged down by more "#ifdef AIX” than I was hoping for (possibly too many differences to factor out the code for AIX, but frankly I don't think so), so I stopped (though I probably was on the right track) - to me it looks like AIX has some extra fixes and differences in the signal code than BSD/Linux.

My question is: given my inability to test on AIX, what can I do to make it easier for AIX developers to adopt this fix? I will try porting my changes again, but in the meantime if anyone has any pointers or offer of other help, I’d appreciate it. I don’t want to straight break AIX port unexpectedly.

Reference: https://bugs.openjdk.java.net/browse/JDK-8252324

Some notes about the affected APIs:

--------------------------------------------------------------------------------------------------
The APIs which moved from os/bsd/os_bsd.cpp (similarly for linux) to to os/posix/PosixSignals.cpp:

////////////////////////////////////////////////////////////////////////////////
// signal support
void os::Bsd::signal_sets_init()
sigset_t* os::Bsd::unblocked_signals()
sigset_t* os::Bsd::vm_signals()
void os::Bsd::hotspot_sigmask(Thread* thread)
////////////////////////////////////////////////////////////////////////////////
// sun.misc.Signal support
static void UserHandler(int sig, void *siginfo, void *context)
void* os::user_handler()
void* os::signal(int signal_number, void* handler)
void os::signal_raise(int signal_number)
int os::sigexitnum_pd()
static void jdk_misc_signal_init()
void os::signal_notify(int sig)
static int check_pending_signals()
int os::signal_wait()
////////////////////////////////////////////////////////////////////////////////
// suspend/resume support
static void resume_clear_context(OSThread *osthread)
static void suspend_save_context(OSThread *osthread, siginfo_t* siginfo, ucontext_t* context)
static void SR_handler(int sig, siginfo_t* siginfo, ucontext_t* context)
static int SR_initialize()
static int sr_notify(OSThread* osthread)
static bool do_suspend(OSThread* osthread)
static void do_resume(OSThread* osthread)
///////////////////////////////////////////////////////////////////////////////////
// signal handling (except suspend/resume)
static void signalHandler(int sig, siginfo_t* info, void* uc)
struct sigaction* os::Bsd::get_chained_signal_action(int sig)
static bool call_chained_handler(struct sigaction *actp, int sig,
                                 siginfo_t *siginfo, void *context)
bool os::Bsd::chained_handler(int sig, siginfo_t* siginfo, void* context)
int os::Bsd::get_our_sigflags(int sig)
void os::Bsd::set_our_sigflags(int sig, int flags)
void os::Bsd::set_signal_handler(int sig, bool set_installed)
void os::Bsd::install_signal_handlers()
static const char* get_signal_handler_name(address handler,
                                           char* buf, int buflen)
static void print_signal_handler(outputStream* st, int sig,
                                 char* buf, size_t buflen)
void os::run_periodic_checks()
void os::Bsd::check_signal_handler(int sig)

-----------------------------------------------------------------------------
The APIs which moved from os/posix/os_posix.cpp to os/posix/PosixSignals.cpp:

const char* os::Posix::get_signal_name(int sig, char* out, size_t outlen)
int os::Posix::get_signal_number(const char* signal_name)
int os::get_signal_number(const char* signal_name)
bool os::Posix::is_valid_signal(int sig)
bool os::Posix::is_sig_ignored(int sig)
const char* os::exception_name(int sig, char* buf, size_t size)
const char* os::Posix::describe_signal_set_short(const sigset_t* set, char* buffer, size_t buf_size)
void os::Posix::print_signal_set_short(outputStream* st, const sigset_t* set)
const char* os::Posix::describe_sa_flags(int flags, char* buffer, size_t size)
oid os::Posix::print_sa_flags(outputStream* st, int flags)
static bool get_signal_code_description(const siginfo_t* si, enum_sigcode_desc_t* out)
void os::print_siginfo(outputStream* os, const void* si0)
bool os::signal_thread(Thread* thread, int sig, const char* reason)
int os::Posix::unblock_thread_signal_mask(const sigset_t *set)
address os::Posix::ucontext_get_pc(const ucontext_t* ctx)
void os::Posix::ucontext_set_pc(ucontext_t* ctx, address pc)
struct sigaction* os::Posix::get_preinstalled_handler(int sig)
void os::Posix::save_preinstalled_handler(int sig, struct sigaction& oldAct)

DETAILS:

--------------------------------------------------------
Public APIs which are now internal static PosixSignals::

sigset_t* os::Bsd::vm_signals()
struct sigaction* os::Bsd::get_chained_signal_action(int sig)
int os::Bsd::get_our_sigflags(int sig)
void os::Bsd::set_our_sigflags(int sig, int flags)
void os::Bsd::set_signal_handler(int sig, bool set_installed)
void os::Bsd::check_signal_handler(int sig)
const char* os::Posix::get_signal_name(int sig, char* out, size_t outlen)
bool os::Posix::is_valid_signal(int sig)
const char* os::Posix::describe_signal_set_short(const sigset_t* set, char* buffer, size_t buf_size)
void os::Posix::print_signal_set_short(outputStream* st, const sigset_t* set)
const char* os::Posix::describe_sa_flags(int flags, char* buffer, size_t size)
oid os::Posix::print_sa_flags(outputStream* st, int flags)
static bool get_signal_code_description(const siginfo_t* si, enum_sigcode_desc_t* out)
void os::Posix::save_preinstalled_handler(int sig, struct sigaction& oldAct)

------------------------------------------------
Public APIs which moved to public PosixSignals::

void os::Bsd::signal_sets_init()
void os::Bsd::hotspot_sigmask(Thread* thread)
bool os::Bsd::chained_handler(int sig, siginfo_t* siginfo, void* context)
void os::Bsd::install_signal_handlers()
bool os::Posix::is_sig_ignored(int sig)
int os::Posix::unblock_thread_signal_mask(const sigset_t *set)
address os::Posix::ucontext_get_pc(const ucontext_t* ctx)
void os::Posix::ucontext_set_pc(ucontext_t* ctx, address pc)

----------------------------------------------------
Internal APIs which are now public in PosixSignals::

static void jdk_misc_signal_init()
static int SR_initialize()
static bool do_suspend(OSThread* osthread)
static void do_resume(OSThread* osthread)
static void print_signal_handler(outputStream* st, int sig,
                                 char* buf, size_t buflen)

--------------------------
New APIs in PosixSignals::

static bool are_signal_handlers_installed();

cheers