From: james.morse@arm•com (James Morse)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v8 4/4] arm64: switch to irq_stack during softirq
Date: Fri, 04 Dec 2015 14:39:44 +0000 [thread overview]
Message-ID: <5661A5B0.3080504@arm.com> (raw)
In-Reply-To: <20151204140119.GL10123@e104818-lin.cambridge.arm.com>
Hi Catalin,
On 04/12/15 14:01, Catalin Marinas wrote:
> On Fri, Dec 04, 2015 at 11:02:28AM +0000, James Morse wrote:
>> +ENTRY(__do_softirq_on_irqstack)
>> + push x19, lr
>> + push x25, x26
>> +
>> + irq_stack_entry lr
>> +
>> + /* irq_stack_entry leaves irq_count in x25 */
>> + ldr x1, [x25]
>> + add x1, x1, #1
>> + str x1, [x25]
>> +
>> + bl __do_softirq
>> +
>> + ldr x1, [x25]
>> + sub x1, x1, #1
>> + str x1, [x25]
>> +
>> + irq_stack_exit
>> +
>> + pop x25, x26
>> + pop x19, lr
>> + ret
>> +ENDPROC(__do_softirq_on_irqstack)
>
> I was thinking of doing do_softirq_own_stack() entirely in assembly
> without the need to check for on_irq_stack() check in C, just a test of
> the irq_count value.
I tried that, but couldn't get it to work - maybe I'm missing a trick:
There are at least two ways into do_softirq_own_stack():
el1_irq() -> __irq_exit() -> do_softirq_own_stack(),
as well as:
cpu_switch_to(ksoftirqd) -> do_softirq_own_stack()
In both cases irq_count == 0 because do_softirq_own_stack() is where we
update irq_count [0]. I can only see two ways to tell them apart,
increment irq_count in el1_irq(), (which we don't like), or have that
bounds checking.
(We could increase hardirq_count() in el?_irq(), which would mean
in_irq()/in_interrupt() always returns true when on the irq_stack, which
would stop softirqs being processed here... but that is a fairly
significant change in behaviour.)
Thanks,
James
[0] http://article.gmane.org/gmane.linux.kernel/2041877
next prev parent reply other threads:[~2015-12-04 14:39 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-04 11:02 [PATCH v8 0/4] arm64: Add support for IRQ stack James Morse
2015-12-04 11:02 ` [PATCH v8 1/4] arm64: Store struct task_info in sp_el0 James Morse
2015-12-04 13:27 ` Catalin Marinas
2015-12-04 14:55 ` James Morse
2015-12-04 16:18 ` Catalin Marinas
2015-12-06 13:15 ` Jungseok Lee
2015-12-04 11:02 ` [PATCH v8 2/4] arm64: Modify stack trace and dump for use with irq_stack James Morse
2015-12-04 12:21 ` Jungseok Lee
2015-12-04 14:31 ` Catalin Marinas
2015-12-04 11:02 ` [PATCH v8 3/4] arm64: Add do_softirq_own_stack() and enable irq_stacks James Morse
2015-12-04 13:46 ` Catalin Marinas
2015-12-04 13:47 ` Catalin Marinas
2015-12-07 22:48 ` Catalin Marinas
2015-12-08 11:43 ` Will Deacon
2015-12-08 16:02 ` Jungseok Lee
2015-12-08 17:23 ` James Morse
2015-12-08 17:27 ` Will Deacon
2015-12-08 23:13 ` Jungseok Lee
2015-12-09 9:47 ` James Morse
2015-12-09 11:38 ` Will Deacon
2015-12-09 13:45 ` Will Deacon
2015-12-09 14:36 ` James Morse
2015-12-04 11:02 ` [PATCH v8 4/4] arm64: switch to irq_stack during softirq James Morse
2015-12-04 14:01 ` Catalin Marinas
2015-12-04 14:39 ` James Morse [this message]
2015-12-04 18:40 ` Catalin Marinas
2015-12-08 10:29 ` James Morse
2015-12-06 13:51 ` Jungseok Lee
2015-12-04 12:17 ` [PATCH v8 0/4] arm64: Add support for IRQ stack Jungseok Lee
2015-12-06 13:56 ` Jungseok Lee
2015-12-04 13:57 ` Catalin Marinas
2015-12-06 13:33 ` Jungseok Lee
2015-12-10 10:22 ` [PATCH v8 5/4] arm64: Fix off-by-one in stack tracing when stepping off irq stack James Morse
2015-12-10 10:22 ` [PATCH v8 6/4] arm64: Add this_cpu_ptr() assembler macro for use in entry.S James Morse
2015-12-10 10:22 ` [PATCH v8 7/4] arm64: when walking onto the task stack, check sp & fp are in current->stack James Morse
2015-12-10 10:22 ` [PATCH v8 8/4] arm64: don't call C code with el0's fp register James Morse
2015-12-10 14:03 ` [PATCH v8 5/4] arm64: Fix off-by-one in stack tracing when stepping off irq stack Jungseok Lee
2015-12-15 11:21 ` [PATCH v8 9/4] arm64: reduce stack use in irq_handler James Morse
2015-12-18 16:01 ` [PATCH v8 9/4] arm64: remove irq_count and do_softirq_own_stack() James Morse
2015-12-20 11:07 ` Jungseok Lee
2015-12-21 11:30 ` Will Deacon
2015-12-21 12:19 ` James Morse
2015-12-21 12:21 ` Will Deacon
2015-12-21 14:06 ` Jungseok Lee
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