[v1,16/21] target/rx: add BQL to do_interrupt and cpu_exec_interrupt

Commit Message

Robert Foley Aug. 5, 2020, 6:12 p.m. UTC

This is part of a series of changes to remove the implied BQL
from the common code of cpu_handle_interrupt and
cpu_handle_exception.  As part of removing the implied BQL
from the common code, we are pushing the BQL holding
down into the per-arch implementation functions of
do_interrupt and cpu_exec_interrupt.

The purpose of this set of changes is to set the groundwork
so that an arch could move towards removing
the BQL from the cpu_handle_interrupt/exception paths.

This approach was suggested by Paolo Bonzini.
For reference, here are two key posts in the discussion, explaining
the reasoning/benefits of this approach.
https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg08731.html
https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg00044.html

Signed-off-by: Robert Foley <[e-mail]>
---
 target/rx/helper.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Patch

diff --git a/target/rx/helper.c b/target/rx/helper.c
index a6a337a311..a456b727ed 100644
--- a/target/rx/helper.c
+++ b/target/rx/helper.c
@@ -48,6 +48,10 @@  void rx_cpu_do_interrupt(CPUState *cs)
     CPURXState *env = &cpu->env;
     int do_irq = cs->interrupt_request & INT_FLAGS;
     uint32_t save_psw;
+    bool bql = !qemu_mutex_iothread_locked();
+    if (bql) {
+        qemu_mutex_lock_iothread();
+    }
 
     env->in_sleep = 0;
 
@@ -117,6 +121,9 @@  void rx_cpu_do_interrupt(CPUState *cs)
                       (vec & 0xff), expname);
     }
     env->regs[0] = env->isp;
+    if (bql) {
+        qemu_mutex_unlock_iothread();
+    }
 }
 
 bool rx_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
@@ -124,6 +131,7 @@  bool rx_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
     RXCPU *cpu = RXCPU(cs);
     CPURXState *env = &cpu->env;
     int accept = 0;
+    qemu_mutex_lock_iothread();
     /* hardware interrupt (Normal) */
     if ((interrupt_request & CPU_INTERRUPT_HARD) &&
         env->psw_i && (env->psw_ipl < env->req_ipl)) {
@@ -138,8 +146,10 @@  bool rx_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
     }
     if (accept) {
         rx_cpu_do_interrupt(cs);
+        qemu_mutex_unlock_iothread();
         return true;
     }
+    qemu_mutex_unlock_iothread();
     return false;
 }