- Do not have boot-mapped buffers use CPU hotplug callbacks
When a ring buffer is mapped to memory assigned at boot, it
also splits it up evenly between the possible CPUs. But the
allocation code still attached a CPU notifier callback to this
ring buffer. When a CPU is added, the callback will happen and
another per-cpu buffer is created for the ring buffer. But for
boot mapped buffers, there is no room to add another one (as
they were all created already). The result of calling the CPU
hotplug notifier on a boot mapped ring buffer is unpredictable
and could lead to a system crash. If the ring buffer is boot mapped
simply do not attach the CPU notifier to it.
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Merge tag 'trace-ringbuffer-v6.12-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing fix from Steven Rostedt:
"Ring-buffer fix: do not have boot-mapped buffers use CPU hotplug
callbacks
When a ring buffer is mapped to memory assigned at boot, it also
splits it up evenly between the possible CPUs. But the allocation code
still attached a CPU notifier callback to this ring buffer. When a CPU
is added, the callback will happen and another per-cpu buffer is
created for the ring buffer.
But for boot mapped buffers, there is no room to add another one (as
they were all created already). The result of calling the CPU hotplug
notifier on a boot mapped ring buffer is unpredictable and could lead
to a system crash.
If the ring buffer is boot mapped simply do not attach the CPU
notifier to it"
* tag 'trace-ringbuffer-v6.12-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
ring-buffer: Do not have boot mapped buffers hook to CPU hotplug
0edab8d132