On Mon, 6 May 2019 18:34:59 -0700 Linus Torvalds torvalds@linux-foundation.org wrote:
On Mon, May 6, 2019 at 6:04 PM Steven Rostedt rostedt@goodmis.org wrote:
That iterator does something special for each individual record. All 40,000 of them.
.. yes, but the 'int3' only happens for *one* of them at a time.
Why would it bother with the other 39,999 calls?
You could easily just look up the record at the int3 time, and just use the record. Exactly the same way you use the one-at-a-time ones.
Instead, you emulate a fake call to a function that *wouldn't* get called, which now does the lookup there. That's the part I don't get. Why are you emulating something else than what you'd be rewriting?
Ah, now I see what you are saying. Yes, I could pass in what it is suppose to call. But I was trying to use the same code for all the alternative solutions we were passing around, and this became the "default" case that would work with any int3_emulate_call implementation we came up with.
That is, if we call ftrace_regs_caller() for any scenario it should work. Even if the call was suppose to be a nop, because in that case, all the ftrace_ops registered in the iterator would refuse to have their handler be called for that function.
I sent you a single patch, but that was really just a diff of several applied patches against your unmodified tree. The last patch implements the ftrace code. And I had it this way because it should work for any of the implementations.
I could modify it so that it picks what function to call when the int3 is triggered. I think all the solutions we are down to allow that now. Some of the early ideas had me call one function for all int3s due to trampolines and such.
Also, I figured just calling ftrace_regs_caller() was simpler then having that int3 handler do the hash look ups to determine what handler it needs to call.
-- Steve