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Subject: Re: [PATCH 3/8] Add a PF flag for ksoftirqd identification
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Venkatesh Pallipadi <venki@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
        "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>,
        Balbir Singh <balbir@linux.vnet.ibm.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        linux-kernel@vger.kernel.org, Paul Turner <pjt@google.com>
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	 <1286237003-12406-4-git-send-email-venki@google.com>
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Date: Fri, 15 Oct 2010 16:46:28 +0200
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Le lundi 04 octobre 2010 à 17:03 -0700, Venkatesh Pallipadi a écrit :
> To account softirq time cleanly in scheduler, we need to identify whether
> softirq is invoked in ksoftirqd context or softirq at hardirq tail context.
> Add PF_KSOFTIRQD for that purpose.
> 
> As all PF flag bits are currently taken, create space by moving one of the
> infrequently used bits (PF_THREAD_BOUND) down in task_struct to be along
> with some other state fields.
> 
> Signed-off-by: Venkatesh Pallipadi <venki@google.com>

Instead of using one bit per task (and fight to find a free bit) why not
using existing :

DEFINE_PER_CPU(struct task_struct *, ksoftirqd);

And check if current is ksoftirqd ?

if (__get_cpu_var(ksoftirqd) == current) ...