Re: Issue with Broadcom wireless in 5.2rc1 (was Re: [PATCH] mmc: sdhci: queue work after sdhci_defer_done())

[Brian Masney]

 On Sun, May 26, 2019 at 03:58:19PM -0400, Brian Masney wrote:
> I attached a patch that shows how I was able to determine what had
> already claimed the host.

I realized this morning that I had a flaw with my test patch that
diagnosed what was deadlocked. The mmc_ctx structure was allocated on
the stack. I attached a second version of that patch that uses
kmalloc() for that structure. It didn't change what I reported
yesterday: brcmf_sdiod_ramrw is deadlocked by
brcmf_sdio_download_firmware.


On Mon, May 27, 2019 at 10:48:24AM +0300, Adrian Hunter wrote:
> This is because SDHCI is using the IRQ thread to process the SDIO card
> interrupt (sdio_run_irqs()).  When the card driver tries to use the card, it
> causes interrupts which deadlocks since c07a48c26519 ("mmc: sdhci: Remove
> finish_tasklet") has moved the tasklet processing to the IRQ thread.
> 
> I would expect to be able to use the IRQ thread to complete requests, and it
> is desirable to do so because it is lower latency.
> 
> Probably, SDHCI should use sdio_signal_irq() which queues a work item, and
> is what other drivers are doing.
> 
> I will investigate some more and send a patch.

Thank you!

Brian