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 <robert.fo...@linaro.org> --- target/lm32/helper.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/target/lm32/helper.c b/target/lm32/helper.c index 1130fc8884..4439b06ecc 100644 --- a/target/lm32/helper.c +++ b/target/lm32/helper.c @@ -152,6 +152,10 @@ void lm32_cpu_do_interrupt(CPUState *cs) { LM32CPU *cpu = LM32_CPU(cs); CPULM32State *env = &cpu->env; + bool bql = !qemu_mutex_iothread_locked(); + if (bql) { + qemu_mutex_lock_iothread(); + } qemu_log_mask(CPU_LOG_INT, "exception at pc=%x type=%x\n", env->pc, cs->exception_index); @@ -196,18 +200,24 @@ void lm32_cpu_do_interrupt(CPUState *cs) cs->exception_index); break; } + if (bql) { + qemu_mutex_unlock_iothread(); + } } bool lm32_cpu_exec_interrupt(CPUState *cs, int interrupt_request) { LM32CPU *cpu = LM32_CPU(cs); CPULM32State *env = &cpu->env; + qemu_mutex_lock_iothread(); if ((interrupt_request & CPU_INTERRUPT_HARD) && (env->ie & IE_IE)) { cs->exception_index = EXCP_IRQ; lm32_cpu_do_interrupt(cs); + qemu_mutex_unlock_iothread(); return true; } + qemu_mutex_unlock_iothread(); return false; } -- 2.17.1
