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SubjectRe: Re: [PATCH 3/4] uprobes/tracing: Kill the pointless local_save_flags/preempt_count calls
(2013/04/04 23:25), Srikar Dronamraju wrote:
> * Oleg Nesterov <oleg@redhat.com> [2013-03-29 19:15:45]:
>
>> uprobe_trace_func() is never called with irqs or preemption
>> disabled, no need to ask preempt_count() or local_save_flags().
>>
>> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
>
> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
>
> Adding Masami in the Cc.

Thanks :), since the running context of uprobe handler is
different from kprobe one, this change is only needed for uprobe.

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Thank you,

>
>> ---
>> kernel/trace/trace_uprobe.c | 10 +++-------
>> 1 files changed, 3 insertions(+), 7 deletions(-)
>>
>> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
>> index 8e00901..43d258d 100644
>> --- a/kernel/trace/trace_uprobe.c
>> +++ b/kernel/trace/trace_uprobe.c
>> @@ -492,17 +492,13 @@ static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
>> struct ring_buffer_event *event;
>> struct ring_buffer *buffer;
>> u8 *data;
>> - int size, i, pc;
>> - unsigned long irq_flags;
>> + int size, i;
>> struct ftrace_event_call *call = &tu->call;
>>
>> - local_save_flags(irq_flags);
>> - pc = preempt_count();
>> -
>> size = sizeof(*entry) + tu->size;
>>
>> event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
>> - size, irq_flags, pc);
>> + size, 0, 0);
>> if (!event)
>> return 0;
>>
>> @@ -513,7 +509,7 @@ static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
>> call_fetch(&tu->args[i].fetch, regs, data + tu->args[i].offset);
>>
>> if (!filter_current_check_discard(buffer, call, entry, event))
>> - trace_buffer_unlock_commit(buffer, event, irq_flags, pc);
>> + trace_buffer_unlock_commit(buffer, event, 0, 0);
>>
>> return 0;
>> }
>> --
>> 1.5.5.1
>>
>


--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com



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