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[Qemu-devel] [RFC DEBUG PATCH 0/3] debug patch for lookup-ptr hang
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [RFC DEBUG PATCH 0/3] debug patch for lookup-ptr hang |
Date: |
Fri, 9 Jun 2017 18:00:57 +0100 |
Hi,
These are debug patches only but represent how much I have narrowed
down the problem so far. I've included Thomas' patch to fix the
thread=single|multi option as that is currently broken upstream. So
far it seems though the problem is unrelated to multi-threading.
As discussed in the other thread I found not returning to a
tb_htable_lookup but adding it to the tb_jmp_cache made the problem go
away. I also tried various printfs but they also seemed to un-wedge
the hang I was seeing. It is not really a hang rather than a busy-spin
that will eventually given enough time unwind.
So added a new TB flag (is_magic) which if set would skip returning
the code ptr and default to exiting the loop via the epilogue and set
it for all DISAS_JUMP/DISAS_UPDATE paths that trigger
lookup_and_goto_ptr. After selectively commenting them out I found the
RET instruction is responsible for my particular fail case.
I find this confusing because BL and BLR basically do the same thing
and they seem to work fine.
I have an uneasy feeling there is some subtle black magic in the
interaction between cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags),
addr and the TCGv cpu_pc but I haven't nailed it down. I'm posting
this for those that still have some Friday left in case it prompts any
thoughts.
Over to you, hopefully inspiration will strike before I return to the
fray on Monday ;-)
Cheers,
Alex Bennée (2):
tcg-runtime: light re-factor of lookup_tb_ptr
translate-a64: fix lookup_tb_ptr hang (DEBUG!)
Thomas Huth (1):
vl: Fix broken thread=xxx option of the --accel parameter
include/exec/exec-all.h | 2 ++
target/arm/translate-a64.c | 21 +++++++++++++++++----
target/arm/translate.h | 2 ++
tcg-runtime.c | 37 +++++++++++++++++++++----------------
vl.c | 13 +++++--------
5 files changed, 47 insertions(+), 28 deletions(-)
--
2.13.0
- [Qemu-devel] [RFC DEBUG PATCH 0/3] debug patch for lookup-ptr hang,
Alex Bennée <=
- [Qemu-devel] [RFC DEBUG PATCH 1/3] vl: Fix broken thread=xxx option of the --accel parameter, Alex Bennée, 2017/06/09
- [Qemu-devel] [RFC DEBUG PATCH 2/3] tcg-runtime: light re-factor of lookup_tb_ptr, Alex Bennée, 2017/06/09
- [Qemu-devel] [RFC DEBUG PATCH 3/3] translate-a64: fix lookup_tb_ptr hang (DEBUG!), Alex Bennée, 2017/06/09
- Re: [Qemu-devel] [RFC DEBUG PATCH 3/3] translate-a64: fix lookup_tb_ptr hang (DEBUG!), Richard Henderson, 2017/06/09
- Re: [Qemu-devel] [RFC DEBUG PATCH 3/3] translate-a64: fix lookup_tb_ptr hang (DEBUG!), Alex Bennée, 2017/06/10
- Re: [Qemu-devel] [RFC DEBUG PATCH 3/3] translate-a64: fix lookup_tb_ptr hang (DEBUG!), Richard Henderson, 2017/06/10
- Re: [Qemu-devel] [RFC DEBUG PATCH 3/3] translate-a64: fix lookup_tb_ptr hang (DEBUG!), Emilio G. Cota, 2017/06/11
- Re: [Qemu-devel] [RFC DEBUG PATCH 3/3] translate-a64: fix lookup_tb_ptr hang (DEBUG!), Alex Bennée, 2017/06/12
- [Qemu-devel] [PATCH] target/aarch64: exit to main loop after handling MSR, Emilio G. Cota, 2017/06/13
- Re: [Qemu-devel] [PATCH] target/aarch64: exit to main loop after handling MSR, no-reply, 2017/06/13