[Qemu-devel] [PULL 10/10] tcg: Remove tb_htable_lookup from helper_lookup_tb_ptr

[Richard Henderson <rth@twiddle.net>]

This appears to induce lockups, or maybe livelocks, while booting an
Alpha Linux kernel.  The assumption is that there is a bug elsewhere
within QEMU, but reverting the patch allows normal work to continue
in the meantime.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg-runtime.c | 32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/tcg-runtime.c b/tcg-runtime.c
index 7fa90ce..cc3bbaf 100644
--- a/tcg-runtime.c
+++ b/tcg-runtime.c
@@ -147,30 +147,24 @@ uint64_t HELPER(ctpop_i64)(uint64_t arg)
 void *HELPER(lookup_tb_ptr)(CPUArchState *env, target_ulong addr)
 {
     CPUState *cpu = ENV_GET_CPU(env);
-    TranslationBlock *tb;
-    target_ulong cs_base, pc;
-    uint32_t flags;
+    unsigned int hash = tb_jmp_cache_hash_func(addr);
+    TranslationBlock *tb = atomic_rcu_read(&cpu->tb_jmp_cache[hash]);
+    void *ret = tcg_ctx.code_gen_epilogue;
 
-    tb = atomic_rcu_read(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(addr)]);
     if (likely(tb)) {
+        target_ulong cs_base, pc;
+        uint32_t flags;
+
         cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
-        if (likely(tb->pc == addr && tb->cs_base == cs_base &&
-                   tb->flags == flags)) {
-            goto found;
-        }
-        tb = tb_htable_lookup(cpu, addr, cs_base, flags);
-        if (likely(tb)) {
-            atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(addr)], tb);
-            goto found;
+        if (tb->pc == addr && tb->cs_base == cs_base && tb->flags == flags) {
+            ret = tb->tc_ptr;
+            qemu_log_mask_and_addr(CPU_LOG_EXEC, addr,
+                                   "Chain %p [%d: " TARGET_FMT_lx "] %s\n",
+                                   ret, cpu->cpu_index, addr,
+                                   lookup_symbol(addr));
         }
     }
-    return tcg_ctx.code_gen_epilogue;
- found:
-    qemu_log_mask_and_addr(CPU_LOG_EXEC, addr,
-                           "Chain %p [%d: " TARGET_FMT_lx "] %s\n",
-                           tb->tc_ptr, cpu->cpu_index, addr,
-                           lookup_symbol(addr));
-    return tb->tc_ptr;
+    return ret;
 }
 
 void HELPER(exit_atomic)(CPUArchState *env)
-- 
2.9.4