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x86: disable X86_PTRACE_BTS

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there's a new ptrace arch level feature in .28:

  config X86_PTRACE_BTS
  bool "Branch Trace Store"

it has broken fork() handling: the old DS area gets copied over into
a new task without clearing it.

Fixes exist but they came too late:

  c5dee61: x86, bts: memory accounting
  bf53de9: x86, bts: add fork and exit handling

and are queued up for v2.6.29. This shows that the facility is still not
tested well enough to release into a stable kernel - disable it for now and
reactivate in .29. In .29 the hardware-branch-tracer will use the DS/BTS
facilities too - hopefully resulting in better code.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2008-12-24 10:49:51 +01:00
parent 280a9ca5d0
commit 40f15ad8aa
1 changed files with 1 additions and 0 deletions
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arch/x86/Kconfig.cpu
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@ -520,6 +520,7 @@ config X86_PTRACE_BTS
bool "Branch Trace Store"
default y
depends on X86_DEBUGCTLMSR
depends on BROKEN
help
This adds a ptrace interface to the hardware's branch trace store.