Re: [Qemu-devel] [PATCH] Make cpu_single_env thread local (Linux only for now)

[Peter Maydell]

On 26 October 2011 15:39, Paolo Bonzini <address@hidden> wrote:
> On 10/26/2011 04:03 PM, Peter Maydell wrote:
>>
>> For the record (since I think we only talked about this on IRC):
>>  * the POSIX TLS fallback code doesn't work on Linux hosts for
>>    linux-user emulation (the constructor is never called to set up
>>    the TLS for the main thread, probably something to do with our
>>    custom linker script, since it does work OK for system emulation)
>>  * if I recall correctly from IRC it doesn't compile on OpenBSD
>>
>> so for 1.0 perhaps we need to fall back to a simpler set of patches
>> that just avoid the regression in thread support for linux-user ?
>
> I agree.

I was thinking something like a trivial qemu-tls.h which does

#ifdef __linux__
#define DECLARE_TLS(type, x) extern DEFINE_TLS(type, x)
#define DEFINE_TLS(type, x)  __thread __typeof__(type) tls__##x
#define get_tls(x)           tls__##x
#else
/* Dummy implementations -- we can get away with this because system
 * mode is effectively single-threaded for our current limited use of
 * TLS, and the only -user mode which supports multiple threads is
 * linux-user.
 * TODO: proper implementations via Win32 .tls sections and
 * POSIX pthread_getspecific.
 */
#define DECLARE_TLS(type, x) extern DEFINE_TLS(type, x)
#define DEFINE_TLS(type, x)  __typeof__(type) tls__##x
#define get_tls(x)           tls__##x
#endif

and then we can just use your "Make cpu_single_env thread-local"
patch as-is:

http://git.linaro.org/gitweb?p=people/pmaydell/qemu-arm.git;a=commitdiff;h=b674559fc8a67ae7d30fe3ab3062d5855ac77d2d

(for that matter we could apply the "Prepare Windows port for
thread-local cpu_single_env" patch too, but that's not a requirement.)

-- PMM