Ah, I see. That's why I saw abnormal behavior when I enabled TLS EMU on an ARMv7 SMP SOC. Many thanks! :) On Fri, Apr 8, 2011 at 10:35 PM, Jamie Lokier <jamie@xxxxxxxxxxxxx> wrote: > Li Li wrote: >> Nicolas, >> >> Thanks for the explanation. :) >> >> I noticed what you mentioned. Actually, Kconfig says TLS EMU might be >> used in some "old" (e.g. pre-armv6) SMP platforms without TLS >> register. In such a case, could we still ensure it's SMP safe by a >> single ldr? > > In that case, the hardware TLS 'mcr' is used, which traps and is > emulated by the undefined instruction handler. It's not fast but > presumably those platforms don't really matter. > > See CONFIG_TLS_REG_EMUL in arch/arm/kernel/traps.c, and 'tls_emu'. > > 'tls_emu' is a constant, so if a kernel built for TLS emulation is run > on something which has the TLS register, it will not work properly. > > -- JAmie > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
