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Re: [Qemu-devel] [RFC 01/10] exec: Introduce tcg_exclusive_{lock, unlock
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [RFC 01/10] exec: Introduce tcg_exclusive_{lock, unlock}() |
Date: |
Wed, 08 Jun 2016 10:21:25 +0100 |
User-agent: |
mu4e 0.9.17; emacs 25.0.94.5 |
Alvise Rigo <address@hidden> writes:
> Add tcg_exclusive_{lock,unlock}() functions that will be used for making
> the emulation of LL and SC instructions thread safe.
I wonder how much similarity there is to the mechanism linus-user ends
up using for it's exclusive-start/end?
>
> Signed-off-by: Alvise Rigo <address@hidden>
> ---
> cpus.c | 2 ++
> exec.c | 18 ++++++++++++++++++
> include/qom/cpu.h | 5 +++++
> 3 files changed, 25 insertions(+)
>
> diff --git a/cpus.c b/cpus.c
> index 860e7ba..b9ec903 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -961,6 +961,8 @@ void qemu_init_cpu_loop(void)
> qemu_cond_init(&qemu_work_cond);
> qemu_mutex_init(&qemu_global_mutex);
>
> + qemu_spin_init(&cpu_exclusive_lock);
> +
> qemu_thread_get_self(&io_thread);
>
> safe_work = g_array_sized_new(TRUE, TRUE, sizeof(qemu_safe_work_item),
> 128);
> diff --git a/exec.c b/exec.c
> index a24b31c..1c72113 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -197,6 +197,24 @@ void cpu_exclusive_history_free(void)
> g_free(excl_history.c_array);
> }
> }
> +
> +__thread bool cpu_have_exclusive_lock;
> +QemuSpin cpu_exclusive_lock;
> +inline void tcg_exclusive_lock(void)
> +{
> + if (!cpu_have_exclusive_lock) {
> + qemu_spin_lock(&cpu_exclusive_lock);
> + cpu_have_exclusive_lock = true;
> + }
> +}
> +
> +inline void tcg_exclusive_unlock(void)
> +{
> + if (cpu_have_exclusive_lock) {
> + cpu_have_exclusive_lock = false;
> + qemu_spin_unlock(&cpu_exclusive_lock);
> + }
> +}
> #endif
>
> #if !defined(CONFIG_USER_ONLY)
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 0f51870..019f06d 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -201,6 +201,11 @@ typedef struct CPUClass {
> void (*disas_set_info)(CPUState *cpu, disassemble_info *info);
> } CPUClass;
>
> +/* Protect cpu_exclusive_* variable .*/
> +void tcg_exclusive_lock(void);
> +void tcg_exclusive_unlock(void);
> +extern QemuSpin cpu_exclusive_lock;
> +
> #ifdef HOST_WORDS_BIGENDIAN
> typedef struct icount_decr_u16 {
> uint16_t high;
--
Alex Bennée