From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: raghu MG <raghumag@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Andrew Lunn <andrew@lunn.ch>
Subject: Re: How is jiffies upation while holding spinlock in Uniprocessor or SMP environment?
Date: Mon, 26 Oct 2015 10:48:54 +0000 [thread overview]
Message-ID: <20151026104854.GC8644@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAG1O52Wq9uCXkOgttQ7gYECQsbFufug2LCBJQfNU309i5QNH6A@mail.gmail.com>
On Mon, Oct 26, 2015 at 12:19:31PM +0530, raghu MG wrote:
> Hello,
> I have couple of questions.
> 1) In case of UP how is jiffies(timer) get updated while holding spin
> lock using spinlock_irq_save?
It isn't, and...
>
> 2)My understanding is in smp environment jiffies updation cannot be
> done on processor holding spinlock irrespective of spinlock API.So
> timer interrupt should be enabled across all cores in SoC. Imagine a
> scenario in quad core processor where 4 cores are holding 4 different
> spinlocks & how is the timer interrupt for jiffies handled?
You can't rely on jiffies being updated while holding a spinlock.
Expecting jiffies to update while holding a spinlock is a bug.
--
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2015-10-26 10:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-26 6:49 raghu MG
2015-10-26 10:48 ` Russell King - ARM Linux [this message]
2015-10-30 10:59 ` raghu MG
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