App-level clone emulation for microblaze is broken

Bug #1066909 reported by Bugdal
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Fix Released

Bug Description

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.

Revision history for this message
Bugdal (bugdal) wrote :

Here is a minimal test case showing the problem.

Revision history for this message
Bugdal (bugdal) wrote :

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:

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.

Aurelien Jarno (aurel32)
Changed in qemu:
status: New → Fix Committed
Thomas Huth (th-huth)
Changed in qemu:
status: Fix Committed → Fix Released
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