linux-kernel - Re: [PATCH] powerpc/udbg_hvc: retry putc on -EAGAIN

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Date:   Sun, 23 May 2021 20:51:09 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Nathan Lynch <nathanl@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        jirislaby@...nel.org
Subject: Re: [PATCH] powerpc/udbg_hvc: retry putc on -EAGAIN

Greg KH <gregkh@...uxfoundation.org> writes:
> On Fri, May 14, 2021 at 04:44:22PM -0500, Nathan Lynch wrote:
>> hvterm_raw_put_chars() calls hvc_put_chars(), which may return -EAGAIN
>> when the underlying hcall returns a "busy" status, but udbg_hvc_putc()
>> doesn't handle this. When using xmon on a PowerVM guest, this can
>> result in incomplete or garbled output when printing relatively large
>> amounts of data quickly, such as when dumping the kernel log buffer.
>> 
>> Call again on -EAGAIN.
>> 
>> Signed-off-by: Nathan Lynch <nathanl@...ux.ibm.com>
>> ---
>>  drivers/tty/hvc/hvc_vio.c | 2 +-
>
> Subject line does not match up with this file name.
>
> Don't you want "tty" and "hvc" in there somewhere?

It's a powerpc only driver, but I guess the subject should still be
"tty: hvc: ..." to match convention.

I was planning to take this via the powerpc tree, but I can drop it if
you'd rather take it.

cheers