From: Lino Sanfilippo <LinoSanfilippo@gmx.de>
To: Jarkko Sakkinen <jarkko@kernel.org>
Cc: peterhuewe@gmx.de, jgg@ziepe.ca, stefanb@linux.vnet.ibm.com,
James.Bottomley@hansenpartnership.com, keescook@chromium.org,
jsnitsel@redhat.com, ml.linux@elloe.vision,
linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/4] tpm: Use a threaded interrupt handler
Date: Thu, 29 Apr 2021 00:37:40 +0200 [thread overview]
Message-ID: <495e816a-afba-4ea0-560c-bc748df26337@gmx.de> (raw)
In-Reply-To: <YIikDCTBcMMxjots@kernel.org>
Hi,
On 28.04.21 at 01:53, Jarkko Sakkinen wrote:
> On Mon, Apr 26, 2021 at 01:47:17AM +0200, Lino Sanfilippo wrote:
>> Interrupt handling at least includes reading and writing the interrupt
>> status register from the interrupt routine. However over SPI those accesses
>> require a sleepable context, since a mutex is used in the concerning
>> functions.
>> For this reason request a threaded interrupt handler which is running in
>> (sleepable) process context.
>>
>> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
>> ---
>> drivers/char/tpm/tpm_tis_core.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
>> index e7d1eab..0959559 100644
>> --- a/drivers/char/tpm/tpm_tis_core.c
>> +++ b/drivers/char/tpm/tpm_tis_core.c
>> @@ -781,8 +781,10 @@ static int tpm_tis_probe_irq_single(struct tpm_chip *chip, u32 intmask,
>> int rc;
>> u32 int_status;
>>
>> - if (devm_request_irq(chip->dev.parent, irq, tis_int_handler, flags,
>> - dev_name(&chip->dev), chip) != 0) {
>> +
>> + if (devm_request_threaded_irq(chip->dev.parent, irq, NULL,
>> + tis_int_handler, IRQF_ONESHOT | flags,
>> + dev_name(&chip->dev), chip) != 0) {
>> dev_info(&chip->dev, "Unable to request irq: %d for probe\n",
>> irq);
>> return -1;
>> --
>> 2.7.4
>>
>
> Why?
>
> https://elixir.bootlin.com/linux/v5.12/source/drivers/char/tpm/tpm_tis_core.c#L670
>
> I don't see anything that sleeps there.
>
> /Jarkko1
>
The problem are the register read/write functions which we use to access the status register in
the interrupt handler. In case of SPI they result in taking the spi_bus_lock which is a mutex.
E.g tpm_tis_spi_read32: tpm_tis_spi_read_bytes->tpm_tis_spi_transfer->spi_bus_lock->mutex_lock
Using a threaded interrupt handler seemed to me the easiest way to avoid this issue.
Regards,
Lino
next prev parent reply other threads:[~2021-04-28 22:37 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-25 23:47 [PATCH v2 0/4] Fixes for TPM interrupt handling Lino Sanfilippo
2021-04-25 23:47 ` [PATCH v2 1/4] tpm: Use a threaded interrupt handler Lino Sanfilippo
2021-04-26 14:37 ` Stefan Berger
2021-04-27 23:53 ` Jarkko Sakkinen
2021-04-28 22:37 ` Lino Sanfilippo [this message]
2021-04-29 6:58 ` Jarkko Sakkinen
2021-05-01 9:01 ` Lino Sanfilippo
2021-04-25 23:47 ` [PATCH v2 2/4] tpm: Simplify locality handling Lino Sanfilippo
2021-04-27 23:49 ` Jarkko Sakkinen
2021-04-28 7:13 ` Peter.Huewe
2021-04-28 22:44 ` Lino Sanfilippo
2021-04-25 23:47 ` [PATCH v2 3/4] tpm: Fix test for interrupts Lino Sanfilippo
2021-04-26 14:49 ` Stefan Berger
2021-04-28 22:13 ` Lino Sanfilippo
2021-04-25 23:47 ` [PATCH v2 4/4] tpm: Only enable supported irqs Lino Sanfilippo
2021-04-26 5:08 ` kernel test robot
2021-04-26 14:23 ` Stefan Berger
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