performance: 0.609
semantic: 0.560
device: 0.537
other: 0.510
network: 0.499
vnc: 0.456
graphic: 0.438
files: 0.415
socket: 0.376
boot: 0.345
PID: 0.335
permissions: 0.308
KVM: 0.115
debug: 0.039

App-level clone emulation for microblaze is broken

When CLONE_THREAD is used, the new process starts with the program counter pointing to the system call instruction, rather than the instruction immediately following it. This causes an infinite cascade (linear growth, not exponential) of thread creation, which quickly crashes when the threads start running and they're all using the same stack.

I'm using qemu 1.1.2 packaged with Debian, but I'm not aware of any fixes since then that would address the problem.

I can provide a test program if needed; a short C program using syscall() directly or an even-shorter asm program can demonstrate the issue without need for debugging around pthread library routines.

Here is a minimal test case showing the problem.


I accidentally posted the patch, which is here, on the wrong bug report (1068900 instead of here). Apologies. For reference here is the patch; it was committed and fixes this issue:

https://lists.eait.uq.edu.au/pipermail/microblaze-linux/2012-October/005760.html

Issue # 1068900, where I mistakenly posted the patch, is unrelated and not fixed; it should be reopened and this issue (1066909) should be marked fixed.