mirror of
https://github.com/torvalds/linux.git
synced 2024-11-08 13:11:45 +00:00
5187b28ff0
With the addition of eagerfpu the irq_fpu_usable() now returns false negatives especially in the case of ksoftirqd and interrupted idle task, two common cases for FPU use for example in networking/crypto. With eagerfpu=off FPU use is possible in those contexts. This is because of the eagerfpu check in interrupted_kernel_fpu_idle(): ... * For now, with eagerfpu we will return interrupted kernel FPU * state as not-idle. TBD: Ideally we can change the return value * to something like __thread_has_fpu(current). But we need to * be careful of doing __thread_clear_has_fpu() before saving * the FPU etc for supporting nested uses etc. For now, take * the simple route! ... if (use_eager_fpu()) return 0; As eagerfpu is automatically "on" on those CPUs that also have the features like AES-NI this patch changes the eagerfpu check to return 1 in case the kernel_fpu_begin() has not been said yet. Once it has been the __thread_has_fpu() will start returning 0. Notice that with eagerfpu the __thread_has_fpu is always true initially. FPU use is thus always possible no matter what task is under us, unless the state has already been saved with kernel_fpu_begin(). [ hpa: this is a performance regression, not a correctness regression, but since it can be quite serious on CPUs which need encryption at interrupt time I am marking this for urgent/stable. ] Signed-off-by: Pekka Riikonen <priikone@iki.fi> Link: http://lkml.kernel.org/r/alpine.GSO.2.00.1305131356320.18@git.silcnet.org Cc: <stable@vger.kernel.org> v3.7+ Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> |
||
|---|---|---|
| .. | ||
| alpha | ||
| arc | ||
| arm | ||
| arm64 | ||
| avr32 | ||
| blackfin | ||
| c6x | ||
| cris | ||
| frv | ||
| h8300 | ||
| hexagon | ||
| ia64 | ||
| m32r | ||
| m68k | ||
| metag | ||
| microblaze | ||
| mips | ||
| mn10300 | ||
| openrisc | ||
| parisc | ||
| powerpc | ||
| s390 | ||
| score | ||
| sh | ||
| sparc | ||
| tile | ||
| um | ||
| unicore32 | ||
| x86 | ||
| xtensa | ||
| .gitignore | ||
| Kconfig | ||