A bug in the ptrace bts extension may cause a kernel crash.
When the ptracer exits, it stops branch tracing for all ptraced tasks
and frees the branch trace buffer. If the traced tasks are currently
running, the branch trace buffer may be freed before the cpu running
that task has stopped tracing, thus overwriting memory with branch
trace data.
Patches 1-4 fix this problem by having the tracer wait for the tracee
to become inactive. This ensures that the cpu has stopped tracing that task.
The bug affects the .29 kernel.
The rest of the patches are for tip/tracing/hw-branch-tracing only.
Patches 5 and 6 fix boot problems caused by the hw-branch-tracer
selftests reported by Ingo Molnar (thanks for reporting the problems).
Patch 8 fixes a bug in the selftest.
Patches 9 and 10 add more selftests.
Patches 7, 11 - 13 are cleanup.
Patch 14 adds support for Core i7.
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