-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 01/13/2015 12:11 PM, Oleg Nesterov wrote: > On 01/11, [email protected] wrote: >> >> Defer restoring the FPU state, if so desired, until the task >> returns to userspace. > > And I have another concern. > > Afaocs with this patch the idle threads will run with TIF_LOAD_FPU > set but without fpu.has_fpu. > > This is fine by itself, but this (performance-wise) breaks > kernel_fpu_begin() if use_eager_fpu() == T. Please see the > changelog in 5187b28ff08249ab8a162e8 and note that this patch cc's > @stable. > > Yes, yes, even if I am right we should blame kernel_fpu_begin() and > other eager_fpu oddities. I tried to start the cleanups/fixes in > this area some time ago, but they were ignored.
I suppose we could make kernel_fpu_begin() explicitly point the cpu's fpu pointer at a special value to indicate that we are in the middle of a kernel_fpu_begin() / kernel_fpu_end() session, and should not use the FPU from interrupt context right now. Does that seem a reasonable fix? - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJUtVvmAAoJEM553pKExN6DmWsH/0V3+3LQBLbOvLVM3h4abS0y 1aI1OqCVzhK4PUChbFwRWsk8IryvGt81n9n9CvnRBOPAg/ZII/NWsWweAVlD4NyL sqaQf8h/mdaUnjoOUzfUmZmhLGtnktMW2beBKfPRbp5ynlLhr0u+kmQ15W2yUio3 Bu/FIhS7THcv/vNBtUfiz6cAaZZGDVrDXGIzxmNSIDTm7tibboZL2VfFI1AjQ+Mw K0iH1tvG1E7n95krapnXHv8GlnzIFgd4yVe8jrLoV4i/045UZKWZbrY/az9VEi++ TFYzMbfJGtFc+MR4AUCed/g1zu2r1lIBNqpjf1GYu/qgJAzF9G07akZnUcITONA= =Vg2Z -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
