linux/arch/x86
Suresh Siddha d75f1b391f x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387_state()
Code paths like fork(), exit() and signal handling flush the fpu
state explicitly to the structures in memory.

BUG_ON() in __sanitize_i387_state() is checking that the fpu state
is not live any more. But for preempt kernels, task can be scheduled
out and in at any place and the preload_fpu logic during context switch
can make the fpu registers live again.

For example, consider a 64-bit Task which uses fpu frequently and as such
you will find its fpu_counter mostly non-zero. During its time slice, kernel
used fpu by doing kernel_fpu_begin/kernel_fpu_end(). After this, in the same
scheduling slice, task-A got a signal to handle. Then during the signal
setup path we got preempted when we are just before the sanitize_i387_state()
in arch/x86/kernel/xsave.c:save_i387_xstate(). And when we come back we
will have the fpu registers live that can hit the bug_on.

Similarly during core dump, other threads can context-switch in and out
(because of spurious wakeups while waiting for the coredump to finish in
 kernel/exit.c:exit_mm()) and the main thread dumping core can run into this
bug when it finds some other thread with its fpu registers live on some other cpu.

So remove the paranoid check for now, even though it caught a bug in the
multi-threaded core dump case (fixed in the previous patch).

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1336692811-30576-3-git-send-email-suresh.b.siddha@intel.com
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2012-05-16 15:17:17 -07:00
..
boot x86, relocs: Remove an unused variable 2012-04-30 12:55:15 -07:00
configs x86/kconfig: Remove CONFIG_TR=y from the defconfigs 2012-03-24 08:18:03 +01:00
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2012-03-22 20:19:30 -07:00
ia32 x86: fix broken TASK_SIZE for ia32_aout 2012-05-06 10:15:18 -07:00
include/asm fork: move the real prepare_to_copy() users to arch_dup_task_struct() 2012-05-16 15:16:26 -07:00
kernel x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387_state() 2012-05-16 15:17:17 -07:00
kvm KVM: ensure async PF event wakes up vcpu from halt 2012-05-06 14:56:54 +03:00
lguest lguest: Make sure interrupt is allocated ok by lguest_setup_irq 2012-01-12 15:44:47 +10:30
lib Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-04-16 18:35:21 -07:00
math-emu x86: Rename trap_no to trap_nr in thread_struct 2012-03-13 06:24:09 +01:00
mm Merge branch 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-29 18:21:35 -07:00
net bpf jit: Let the x86 jit handle negative offsets 2012-04-03 18:01:41 -04:00
oprofile x86: Factor out TIF_IA32 from 32-bit address space 2012-02-20 12:48:46 -08:00
pci Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci 2012-03-23 14:02:12 -07:00
platform arch/x86/platform/geode/net5501.c: change active_low to 0 for LED driver 2012-05-04 14:40:07 -07:00
power x86, kvm: Call restore_sched_clock_state() only after %gs is initialized 2012-04-02 13:53:00 +02:00
syscalls Merge branch 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-29 18:12:23 -07:00
tools x86/tools: Add decoded instruction dump mode 2011-12-05 14:53:23 +01:00
um um: Use asm-generic/switch_to.h 2012-04-10 00:13:45 +02:00
vdso Merge branch 'x86-x32-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-03-29 18:12:23 -07:00
video x86: fix up files really needing to include module.h 2011-10-31 19:30:36 -04:00
xen xen/pci: don't use PCI BIOS service for configuration space accesses 2012-05-07 12:16:21 -04:00
.gitignore x86/kprobes: Add arch/x86/tools/insn_sanity to .gitignore 2012-01-16 08:21:59 +01:00
Kbuild
Kconfig vfs: make word-at-a-time accesses handle a non-existing page 2012-05-03 14:01:40 -07:00
Kconfig.cpu x86: Tighten dependencies of CPU_SUP_*_32 2012-03-08 10:57:34 +01:00
Kconfig.debug Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-11 19:13:40 -08:00
Makefile x86: Use -mno-avx when available 2012-03-30 10:06:39 -07:00
Makefile.um um: fix linker script generation 2012-04-09 13:59:00 -04:00
Makefile_32.cpu