tracing: Add snapshot refcount

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When a ring-buffer is memory mapped by user-space, no trace or
ring-buffer swap is possible. This means the snapshot feature is
mutually exclusive with the memory mapping. Having a refcount on
snapshot users will help to know if a mapping is possible or not.

Instead of relying on the global trace_types_lock, a new spinlock is
introduced to serialize accesses to trace_array->snapshot. This intends
to allow access to that variable in a context where the mmap lock is
already held.

Link: https://lore.kernel.org/linux-trace-kernel/20240220202310.2489614-4-vdonnefort@google.com

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

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Vincent Donnefort 2024-02-20 20:23:07 +00:00 • committed by Steven Rostedt (Google)

parent b70f293824

commit 180e4e3909

3 changed files with 129 additions and 36 deletions

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99

kernel/trace/trace.c

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8

kernel/trace/trace.h

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58

kernel/trace/trace_events_trigger.c

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