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Re: [Qemu-devel] [PATCH 03/10] replace spinlock by QemuMutex.
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 03/10] replace spinlock by QemuMutex. |
Date: |
Thu, 13 Aug 2015 15:12:31 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
On 13/08/2015 14:17, Frederic Konrad wrote:
>> diff --git a/linux-user/main.c b/linux-user/main.c
>> index fdee981..fd06ce9 100644
>> --- a/linux-user/main.c
>> +++ b/linux-user/main.c
>> @@ -107,7 +107,7 @@ static int pending_cpus;
>> /* Make sure everything is in a consistent state for calling
>> fork(). */
>> void fork_start(void)
>> {
>> - pthread_mutex_lock(&tcg_ctx.tb_ctx.tb_lock);
>> + qemu_mutex_lock(&tcg_ctx.tb_ctx.tb_lock);
>> pthread_mutex_lock(&exclusive_lock);
>> mmap_fork_start();
>> }
>> @@ -129,11 +129,11 @@ void fork_end(int child)
>> pthread_mutex_init(&cpu_list_mutex, NULL);
>> pthread_cond_init(&exclusive_cond, NULL);
>> pthread_cond_init(&exclusive_resume, NULL);
>> - pthread_mutex_init(&tcg_ctx.tb_ctx.tb_lock, NULL);
>> + qemu_mutex_init(&tcg_ctx.tb_ctx.tb_lock);
>> gdbserver_fork(thread_cpu);
>> } else {
>> pthread_mutex_unlock(&exclusive_lock);
>> - pthread_mutex_unlock(&tcg_ctx.tb_ctx.tb_lock);
>> + qemu_mutex_unlock(&tcg_ctx.tb_ctx.tb_lock);
> We might want to use tb_lock/unlock in user code as well instead of
> calling directly qemu_mutex_* ?
You cannot do that because of the recursive locking assertions; the
child is not using qemu_mutex_unlock, it's using qemu_mutex_init. So I
would have to add some kind of tb_lock_reset_after_fork() function which
is a bit ugly.
>> @@ -676,6 +709,7 @@ static inline void code_gen_alloc(size_t tb_size)
>> CODE_GEN_AVG_BLOCK_SIZE;
>> tcg_ctx.tb_ctx.tbs =
>> g_malloc(tcg_ctx.code_gen_max_blocks *
>> sizeof(TranslationBlock));
>> + qemu_mutex_init(&tcg_ctx.tb_ctx.tb_lock);
> Maybe we can initialize the mutex only for CONFIG_USER_ONLY?
It's okay, it doesn't consume system resources.
Paolo
- Re: [Qemu-devel] [PATCH 02/10] cpus: remove tcg_halt_cond global variable., (continued)
[Qemu-devel] [PATCH 07/10] tcg: comment on which functions have to be called with mmap_lock held, Paolo Bonzini, 2015/08/12
[Qemu-devel] [PATCH 01/10] cpus: protect work list with work_mutex, Paolo Bonzini, 2015/08/12
[Qemu-devel] [PATCH 08/10] tcg: add memory barriers in page_find_alloc accesses, Paolo Bonzini, 2015/08/12