Re: [PATCH] mmc: sdhci: disable irq in sdhci host suspend ranther than free this irq

[Peng Fan]

Hi All,

Sorry for bring back this old topic again.

On Thu, Jan 28, 2016 at 05:27:46PM +0100, Thomas Gleixner wrote:
>On Thu, 28 Jan 2016, Thomas Gleixner wrote:
>> On Thu, 28 Jan 2016, Ulf Hansson wrote:
>> > Therefore, the only way we currently can make sure to don't get the
>> > IRQ is to free and later re-request it. Now, apparently that has
>> > issues when using threaded IRQ handlers.
>> 
>> What's the issue?
>
>Ah, you mean that one:
>
>> Currently sdhci driver free irq in host suspend, and call
>> request_threaded_irq() in host resume. But during host resume,
>> Ctrl+C can impact sdhci host resume, see the error log:
>
>> CPU1 is up
>> PM: noirq resume of devices complete after 0.637 msecs imx-sdma 30bd0000.sdma: loaded firmware 4.1
>> PM: early resume of devices complete after 0.774 msecs
>> dpm_run_callback(): platform_pm_resume+0x0/0x44 returns -4
>> PM: Device 30b40000.usdhc failed to resume: error -4
>> dpm_run_callback(): platform_pm_resume+0x0/0x44 returns -4
>> PM: Device 30b50000.usdhc failed to resume: error -4
>> dpm_run_callback(): platform_pm_resume+0x0/0x44 returns -4
>> PM: Device 30b60000.usdhc failed to resume: error -4 fec 30be0000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
>> mmc0: Timeout waiting for hardware interrupt.
>> mmc0: Timeout waiting for hardware interrupt.
>> mmc0: Timeout waiting for hardware interrupt.
>> mmc0: Timeout waiting for hardware interrupt.
>> mmc0: Timeout waiting for hardware interrupt.
>> mmc0: Timeout waiting for hardware interrupt.
>> mmc0: error -110 during resume (card was removed?)
>> mmc2: Timeout waiting for hardware interrupt.
>> mmc2: Timeout waiting for hardware interrupt.
>> mmc2: error -110 during resume (card was removed?)
>
>In request_threaded_irq-> __setup_irq-> kthread_create
>->kthread_create_on_node, the comment shows that SIGKILLed will
>impact the kthread create, and return -EINTR.
>
>And how should that thread be SIGKILLed? Hitting Ctrl+C on the console does
>not affect any kernel internal thread. Hitting Ctrl+C affects solely the
>process which is running on that console.
>
>And if it would, then that would be a completely different, serious bug which
>needs to be fixed.
>
>How was verified, that the thread was not created and that the creation failed
>due to a SIGKILL?

This is the testcase.
"/unit_tests/SRTC/rtcwakeup.out -d rtc0 -m mem -s 2;"
it acts "echo mem > /sys/power/state", then rtc interrupt will wakeup the system.

My understanding is:
The issue is during suspend resume, it is in rtwakeup.out process space,
during resume, "get_current()->comm" shows "rtcwakeup.out", so if we
send SIGKILL from userspace, a interrupt will occur, interrupt
handler will directly return to kernel space to continue resuming.

__setup_irq->kthread_create->wait_for_completion_killable, here
wait_for_completion_killable see SIGKILL pending and return -EINTR,
then sdhci resume process failure, because of sdhci interrupt thread
not created.

During suspend/resume, OOM Killer will be disabled and enalbed. When
request_threaded_irq in sdhci resume, OOM Killer is still disabled.
According to kthread_create comments for wait_for_completion_killable,
using killable is to catch OOM sigkill. But during resume, OOM Killer
is disabled, So how about the following patch to disable SIGKILL for
a short while?

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index e9290a3439d5..84c4c99b1acb 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -19,6 +19,7 @@
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/dma-mapping.h>
+#include <linux/signal.h>
 #include <linux/slab.h>
 #include <linux/scatterlist.h>
 #include <linux/swiotlb.h>
@@ -2895,9 +2896,11 @@ int sdhci_resume_host(struct sdhci_host *host)
 	}
 
 	if (!device_may_wakeup(mmc_dev(host->mmc))) {
+		disallow_signal(SIGKILL);
 		ret = request_threaded_irq(host->irq, sdhci_irq,
 					   sdhci_thread_irq, IRQF_SHARED,
 					   mmc_hostname(host->mmc), host);
+		allow_signal(SIGKILL);
 		if (ret)
 			return ret;
 	} else {

Thanks,
Peng.

>
>Thanks,
>
>	tglx

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