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Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only fo
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now) |
Date: |
Tue, 04 Oct 2011 19:26:48 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 2011-10-04 17:10, Lluís Vilanova wrote:
> Jan Kiszka writes:
>
>> On 2011-10-03 18:33, Dr. David Alan Gilbert wrote:
>>> Make cpu_single_env thread local (Linux only for now)
>>> * Fixes some user space threading issues (esp those triggered
>>> by bug 823902)
>>>
>>> Against rev d11cf8cc..., tested on ARM user mode, and ARM Vexpress
>>> system mode (with Blue Swirl's fix from yesterday) - only
>>> tested on Linux host. Lets me run ARM userspace firefox.
>>>
>>> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
>>>
>>> diff --git a/cpu-all.h b/cpu-all.h
>>> index 42a5fa0..d895ee6 100644
>>> --- a/cpu-all.h
>>> +++ b/cpu-all.h
>>> @@ -334,7 +334,13 @@ void cpu_dump_statistics(CPUState *env, FILE *f,
>>> fprintf_function cpu_fprintf,
>>> void QEMU_NORETURN cpu_abort(CPUState *env, const char *fmt, ...)
>>> GCC_FMT_ATTR(2, 3);
>>> extern CPUState *first_cpu;
>>> +
>>> +#ifdef __linux__
>>> +/* DAG: Only tested thread local on Linux, feel free to add others */
>>> +extern __thread CPUState *cpu_single_env;
>>> +#else
>>> extern CPUState *cpu_single_env;
>>> +#endif
>
>> We need this for all platforms in order to skip qemu_global_mutex while
>> manipulating some CPUState. And leaving some platforms with non-TLS will
>> eventually break them when code is added that assumes TLS.
>
>> However, it's not unlikely that some weird platforms / ancient
>> toolchains still have problems with __thread - even on Linux. We may
>> want to play safe and use pthread_key on POSIX.
>
> Why not make this kind of annotations available in qemu-commmon.h; or even
> better somewhere less... "generic".
Yes, we will need some encapsulation for this.
>
> #if defined(CONFIG_SUPPORTS_THREAD_KEYWORD)
>
> // use __thread
> #define QEMU_DECL_TLS(type, name) \
> extern __thread type name;
> #define QEMU_DEF_TLS(type, name) \
> __thread type name;
> #define QEMU_SET_TLS(name, value) \
> do { name = value; } while (0)
> #define QEMU_GET_TLS(name) \
> name
>
> #elif defined(CONFIG_SUPPORTS_PTHREAD_KEY)
>
> // use pthread_key_t
> #define QEMU_DECL_TLS(type, name) \
> extern type _type_##name; \
> extern pthread_key_t name;
> #define QEMU_DEF_TLS(type, name) \
> pthread_key_t name; \
> void _init_##name (void) __attribute__((constructor)); \
> void _init_##name (void) { pthread_key_create(&name, NULL); }
> #define QEMU_SET_TLS(name, value) \
> do { pthread_setspecific(name, (void*)value); } while (0)
> #define QEMU_GET_TLS(name) \
> ((typeof(_type_##name))pthread_getspecific(name))
>
> #else
> #error Go home
> #endif
Looks like a start. But I would avoid macros and go for (static inline)
functions where possible. And initialization should be explicit (so that
you can start using TLS already inside constructors).
Jan
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- [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Dr. David Alan Gilbert, 2011/10/03
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Jan Kiszka, 2011/10/03
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Lluís Vilanova, 2011/10/04
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now),
Jan Kiszka <=
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Paolo Bonzini, 2011/10/05
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Jan Kiszka, 2011/10/05
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Paolo Bonzini, 2011/10/05
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), David Gilbert, 2011/10/07
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Paolo Bonzini, 2011/10/08
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Peter Maydell, 2011/10/26
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Paolo Bonzini, 2011/10/26
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Peter Maydell, 2011/10/26
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Paolo Bonzini, 2011/10/26
- Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now), Jan Kiszka, 2011/10/26