Re: [PATCH] remove duplicate irq instrumentation for MIPS

Tim Bird wrote:
> This patch removes MIPS-specific irq entry and exit instrumentation.
> 
> I was getting duplicate events for each irq entry and exit
> on a MIPS machine.  I believe this was left over from before
> the use of generic interrupt handling by the MIPS arch.
> The instrumentation points in handle_IRQ_event() now seem
> to generate the appropriate events.

Here is some more information on this.  I got the bug
report from Takuzo O'hara, from Sony in Japan.
He wrote:
> [The current patch] adds a trace point for IRQ event in
> arch/mips/kernel/irq.c:do_IRQ(), even though the same event is
> recorded in kernel/irq/handle.c:handle_IRQ_event().
> 
> Thus the LTT trace for MIPS shows two events for every IRQ.
> 
> This is a sample trace, extracting two timer interrupt event.
> (IRQ=199 is timer interrupt on our board, with HZ=1000).
> 
> ----------------
> kernel.irq_entry: 120.583128973 (/cpu_0), 693, lttctl, 692, 0x0, IRQ { irq_id = 199, mode = user }
> kernel.irq_entry: 120.583135229 (/cpu_0), 693, lttctl, 692, 0x0, IRQ { irq_id = 199, mode = user }
> kernel.irq_exit: 120.583150225 (/cpu_0), 693, lttctl, 692, 0x0, IRQ
> kernel.irq_exit: 120.583155554 (/cpu_0), 693, lttctl, 692, 0x0, SYSCALL
> kernel.irq_entry: 120.584128820 (/cpu_0), 693, lttctl, 692, 0x0, IRQ { irq_id = 199, mode = kernel }
> kernel.irq_entry: 120.584135296 (/cpu_0), 693, lttctl, 692, 0x0, IRQ { irq_id = 199, mode = kernel }
> kernel.irq_exit: 120.584151928 (/cpu_0), 693, lttctl, 692, 0x0, IRQ
> kernel.irq_exit: 120.584156689 (/cpu_0), 693, lttctl, 692, 0x0, SYSCALL
> ----------------

Technically, the patch should have been:

Signed-off-by: Takuzo O'hara <[email protected]>
Acked-by: Tim Bird <[email protected]>

Just want to make sure I give credit where credit is due.
 -- Tim

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Electronics
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