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authorLen Brown <len.brown@intel.com>2012-03-29 14:49:17 -0700
committerIngo Molnar <mingo@kernel.org>2012-03-30 08:50:27 +0200
commitf6365201d8a21fb347260f89d6e9b3e718d63c70 (patch)
tree539319cc79dcfb2fbc812c3acbda76f61a4a02fa /arch/x86
parent186e54cbe1145f4d11e32fe10e7e20a11f1b27dd (diff)
x86: Remove the ancient and deprecated disable_hlt() and enable_hlt() facility
The X86_32-only disable_hlt/enable_hlt mechanism was used by the 32-bit floppy driver. Its effect was to replace the use of the HLT instruction inside default_idle() with cpu_relax() - essentially it turned off the use of HLT. This workaround was commented in the code as: "disable hlt during certain critical i/o operations" "This halt magic was a workaround for ancient floppy DMA wreckage. It should be safe to remove." H. Peter Anvin additionally adds: "To the best of my knowledge, no-hlt only existed because of flaky power distributions on 386/486 systems which were sold to run DOS. Since DOS did no power management of any kind, including HLT, the power draw was fairly uniform; when exposed to the much hhigher noise levels you got when Linux used HLT caused some of these systems to fail. They were by far in the minority even back then." Alan Cox further says: "Also for the Cyrix 5510 which tended to go castors up if a HLT occurred during a DMA cycle and on a few other boxes HLT during DMA tended to go astray. Do we care ? I doubt it. The 5510 was pretty obscure, the 5520 fixed it, the 5530 is probably the oldest still in any kind of use." So, let's finally drop this. Signed-off-by: Len Brown <len.brown@intel.com> Signed-off-by: Josh Boyer <jwboyer@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: "H. Peter Anvin" <hpa@zytor.com> Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Stephen Hemminger <shemminger@vyatta.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: <stable@kernel.org> Link: http://lkml.kernel.org/n/tip-3rhk9bzf0x9rljkv488tloib@git.kernel.org [ If anyone cares then alternative instruction patching could be used to replace HLT with a one-byte NOP instruction. Much simpler. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/include/asm/processor.h10
-rw-r--r--arch/x86/kernel/process.c24
2 files changed, 0 insertions, 34 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 7284c9a6a0b..4fa7dcceb6c 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -974,16 +974,6 @@ extern bool cpu_has_amd_erratum(const int *);
#define cpu_has_amd_erratum(x) (false)
#endif /* CONFIG_CPU_SUP_AMD */
-#ifdef CONFIG_X86_32
-/*
- * disable hlt during certain critical i/o operations
- */
-#define HAVE_DISABLE_HLT
-#endif
-
-void disable_hlt(void);
-void enable_hlt(void);
-
void cpu_idle_wait(void);
extern unsigned long arch_align_stack(unsigned long sp);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index a33afaa5ddb..1d92a5ab6e8 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -362,34 +362,10 @@ void (*pm_idle)(void);
EXPORT_SYMBOL(pm_idle);
#endif
-#ifdef CONFIG_X86_32
-/*
- * This halt magic was a workaround for ancient floppy DMA
- * wreckage. It should be safe to remove.
- */
-static int hlt_counter;
-void disable_hlt(void)
-{
- hlt_counter++;
-}
-EXPORT_SYMBOL(disable_hlt);
-
-void enable_hlt(void)
-{
- hlt_counter--;
-}
-EXPORT_SYMBOL(enable_hlt);
-
-static inline int hlt_use_halt(void)
-{
- return (!hlt_counter && boot_cpu_data.hlt_works_ok);
-}
-#else
static inline int hlt_use_halt(void)
{
return 1;
}
-#endif
#ifndef CONFIG_SMP
static inline void play_dead(void)