| Message ID | 1283954337-28760-1-git-send-email-jakllsch@kollasch.net |
|---|---|
| State | New |
| Headers | show |
On Wed, 8 Sep 2010, Jonathan A. Kollasch wrote: > Change the accumulator only after performing the redundant write during > cmpxchg. This fixes pthreaded programs using fork() in NetBSD/i386 > guests. > > >From Andreas Gustafsson in https://bugs.launchpad.net/qemu/+bug/569760. This is tab damaged. Secondly it looks as if this addresses only a small part of a general problem [1], also in a very naive and inefficient way, while also opening a hole can of worms (should real parallel execution for TCG be ever implemented) [1] http://www.mail-archive.com/qemu-devel@nongnu.org/msg40000.html > > Signed-off-by: Jonathan A. Kollasch <jakllsch@kollasch.net> > --- > target-i386/translate.c | 12 ++++++++---- > 1 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/target-i386/translate.c b/target-i386/translate.c > index 7b6e3c2..391830f 100644 > --- a/target-i386/translate.c > +++ b/target-i386/translate.c > @@ -4879,20 +4879,24 @@ static target_ulong disas_insn(DisasContext *s, target_ulong pc_start) > tcg_gen_sub_tl(t2, cpu_regs[R_EAX], t0); > gen_extu(ot, t2); > tcg_gen_brcondi_tl(TCG_COND_EQ, t2, 0, label1); > + label2 = gen_new_label(); > if (mod == 3) { > - label2 = gen_new_label(); > gen_op_mov_reg_v(ot, R_EAX, t0); > tcg_gen_br(label2); > gen_set_label(label1); > gen_op_mov_reg_v(ot, rm, t1); > - gen_set_label(label2); > } else { > - tcg_gen_mov_tl(t1, t0); > + /* perform no-op store cycle like physical cpu; must be > + before changing accumulator to ensure idempotency if > + the store faults and the instruction is restarted > + */ > + gen_op_st_v(ot + s->mem_index, t0, a0); > gen_op_mov_reg_v(ot, R_EAX, t0); > + tcg_gen_br(label2); > gen_set_label(label1); > - /* always store */ > gen_op_st_v(ot + s->mem_index, t1, a0); > } > + gen_set_label(label2); > tcg_gen_mov_tl(cpu_cc_src, t0); > tcg_gen_mov_tl(cpu_cc_dst, t2); > s->cc_op = CC_OP_SUBB + ot; >
diff --git a/target-i386/translate.c b/target-i386/translate.c index 7b6e3c2..391830f 100644 --- a/target-i386/translate.c +++ b/target-i386/translate.c @@ -4879,20 +4879,24 @@ static target_ulong disas_insn(DisasContext *s, target_ulong pc_start) tcg_gen_sub_tl(t2, cpu_regs[R_EAX], t0); gen_extu(ot, t2); tcg_gen_brcondi_tl(TCG_COND_EQ, t2, 0, label1); + label2 = gen_new_label(); if (mod == 3) { - label2 = gen_new_label(); gen_op_mov_reg_v(ot, R_EAX, t0); tcg_gen_br(label2); gen_set_label(label1); gen_op_mov_reg_v(ot, rm, t1); - gen_set_label(label2); } else { - tcg_gen_mov_tl(t1, t0); + /* perform no-op store cycle like physical cpu; must be + before changing accumulator to ensure idempotency if + the store faults and the instruction is restarted + */ + gen_op_st_v(ot + s->mem_index, t0, a0); gen_op_mov_reg_v(ot, R_EAX, t0); + tcg_gen_br(label2); gen_set_label(label1); - /* always store */ gen_op_st_v(ot + s->mem_index, t1, a0); } + gen_set_label(label2); tcg_gen_mov_tl(cpu_cc_src, t0); tcg_gen_mov_tl(cpu_cc_dst, t2); s->cc_op = CC_OP_SUBB + ot;
Change the accumulator only after performing the redundant write during cmpxchg. This fixes pthreaded programs using fork() in NetBSD/i386 guests. From Andreas Gustafsson in https://bugs.launchpad.net/qemu/+bug/569760. Signed-off-by: Jonathan A. Kollasch <jakllsch@kollasch.net> --- target-i386/translate.c | 12 ++++++++---- 1 files changed, 8 insertions(+), 4 deletions(-)