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20fb6c9976
The mmiotrace tracer is "special". The purpose is to help reverse engineer binary drivers by removing the memory allocated by the driver and when the driver goes to access it, a fault occurs, the mmiotracer will record what the driver was doing and then do the work on its behalf by single stepping through the process. But to achieve this ability, it must do some special things. One is to take the rcu_read_lock() when the fault occurs, and then release it in the breakpoint that is single stepping. This makes lockdep unhappy, as it changes the state of RCU from within an exception that is not contained in that exception, and we get a nasty splat from lockdep. Instead, switch to rcu_read_lock_sched_notrace() as the RCU sched variant has the same grace period as normal RCU. This is basically the same as rcu_read_lock() but does not make lockdep complain about it. Note, the preempt_disable() is still needed as it uses preempt_enable_no_resched(). Link: https://lore.kernel.org/linux-trace-kernel/20221209134144.04f33626@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Karol Herbst <karolherbst@gmail.com> Cc: Pekka Paalanen <ppaalanen@gmail.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
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