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    SubjectRe: Boot stall regression from "printk for 5.19" merge
    +Cc: Ilpo, a new maintainer for the driver

    On Mon, Jun 20, 2022 at 12:46 PM Marek Behún <kabel@kernel.org> wrote:
    >
    > On Mon, 20 Jun 2022 19:13:37 +0900
    > Sergey Senozhatsky <senozhatsky@chromium.org> wrote:
    >
    > > On (22/06/20 12:02), Marek Behún wrote:
    > > > > On (22/06/19 20:49), Marek Behún wrote:
    > > > > [..]
    > > > > > causes a regression on arm64 (Marvell CN9130-CRB board) where the
    > > > > > system boot freezes in most cases (and is unusable until restarted by
    > > > > > watchdog), or, in some cases boots, but the console output gets mangled
    > > > > > for a while (the serial console spits garbage characters).
    > > > >
    > > > > Can you please try disabling console kthreads and see how the boot
    > > > > process goes? Just `return 0` from printk_activate_kthreads() (I think
    > > > > this should do the trick).
    > > >
    > > > This indeed makes the problem go away...
    > >
    > > Oh... OK. Didn't expect that :)
    > >
    > > > > > The garbage example:
    > > > > >
    > > > > > ...
    > > > > > [ 0.920951] raid6: using neon recovery algorithm
    > > > > > [ 0.921228] iommu: Default domain type: Translated
    > > > > > %
    > > > > >
    > > > > > gb@k+cFL/[ 4.954974] DSA: tree 0 setup
    > > > > > [ 4.955286] cfg80211: Loading compiled-in X.509 certificates for regulatory database
    > > > >
    > > > > This is pretty suspicious. I don't see how console kthreads would
    > > > > corrupt the output. I suspect that something else is going on, some
    > > > > memory corruption, etc.
    > > >
    > > > Maybe multiple threads are writing to serial registers, or something...
    > >
    > > That's possible. Console drivers usually should grab port->lock for
    > > write(), but maybe something is missing in the driver you use. What
    > > console driver are you using?
    >
    > compatible = "snps,dw-apb-uart", so drivers/tty/serial/8250/8250_dw.c
    >
    > seems that the function dw8250_serial_out() does not use the spinlock...
    >
    > Marek



    --
    With Best Regards,
    Andy Shevchenko

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