I believe the problem is that the VM is now using more atomic load/store of java longs and we don’t support these operations on multi-processing ARMv5 systems due to the lack of low level atomic instructions. On non MP ARMv5 systems, we use load/store multiple instructions.
If you can determine that your ARMv5 processor’s implementation of ldmia/stmia are indeed atomic, you could try to use these instructions by altering the code below. Otherwise, you might want to investigate gcc atomic intrinsics and see if 8 byte atomics are supported on your platform. There’s a set of kernel helper routines that we use for atomic exchange of 8 bytes, maybe they now have atomic 8 byte loads/stores. https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html https://www.kernel.org/doc/Documentation/arm/kernel_user_helpers.txt In open/src/hotspot/cpu/arm/stubGenerator_arm.cpp, these two functions would need to be fixed to provide these low level operations. address generate_atomic_load_long() { address start; StubCodeMark mark(this, "StubRoutines", "atomic_load_long"); start = __ pc(); Register result_lo = R0; Register result_hi = R1; Register src = R0; if (!os::is_MP()) { __ ldmia(src, RegisterSet(result_lo, result_hi)); __ bx(LR); } else if (VM_Version::supports_ldrexd()) { __ ldrexd(result_lo, Address(src)); __ clrex(); // FIXME: safe to remove? __ bx(LR); } else { __ stop("Atomic load(jlong) unsupported on this platform"); __ bx(LR); } return start; } address generate_atomic_store_long() { address start; StubCodeMark mark(this, "StubRoutines", "atomic_store_long"); start = __ pc(); Register newval_lo = R0; Register newval_hi = R1; Register dest = R2; Register scratch_lo = R2; Register scratch_hi = R3; /* After load from stack */ Register result = R3; if (!os::is_MP()) { __ stmia(dest, RegisterSet(newval_lo, newval_hi)); __ bx(LR); } else if (VM_Version::supports_ldrexd()) { __ mov(Rtemp, dest); // get dest to Rtemp Label retry; __ bind(retry); __ ldrexd(scratch_lo, Address(Rtemp)); __ strexd(result, R0, Address(Rtemp)); __ rsbs(result, result, 1); __ b(retry, eq); __ bx(LR); } else { __ stop("Atomic store(jlong) unsupported on this platform"); __ bx(LR); } return start; } Bob. > On Apr 4, 2018, at 11:06 AM, John Paul Adrian Glaubitz > <glaub...@physik.fu-berlin.de> wrote: > > CC'ing hotspot-dev > > On 04/04/2018 12:29 PM, b...@juanantonio.info wrote: >> I think that in OpenJDK10 changed something in compare to OpenJDK9 in >> relation to ARM5 support. > > It was OpenJDK9 which dropped support for ARM CPUs prior ARMv7. If you are > using ARMv5, you have to resort to OpenJDK Zero, i.e. the unoptimized, generic > implementation of the JVM. > > As for the atomic operation, I'm not sure whether Zero supports this > particular > atomic operation. I will have to dig into the code myself. > > Would it be possible that you provide sample code that helps reproduce the > problem? > > Adrian > > -- > .''`. John Paul Adrian Glaubitz > : :' : Debian Developer - glaub...@debian.org > `. `' Freie Universitaet Berlin - glaub...@physik.fu-berlin.de > `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
