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Re: [Xen-devel] linux 4.19 xenstore memory allocation failure Re: [linux-4.19 test] 135420: regressions - FAIL

On Thu, May 02, 2019 at 11:42:04AM +0100, Ian Jackson wrote:
> Roger Pau Monne writes ("Re: [Xen-devel] linux 4.19 xenstore memory 
> allocation failure Re: [linux-4.19 test] 135420: regressions - FAIL"):
> > On Wed, May 01, 2019 at 10:47:49AM +0100, Ian Jackson wrote:
> > > What if you can't write to xenstore ?  Can we at least have a copy in
> > > the kernel log ?  There might be other errors besides this memory
> > > exhaustion, surely.
> > 
> > There's a call to dev_err also, which should print the same error
> > that's written to xenstore on the console. That however requires the
> > memory allocation of page in order to format the string to be printed
> > (see xenbus_va_dev_error).
> Can we assume that memory exhaustion will always result in some
> message from the memory allocator ?  If so then this new log message

I'm not sure I understand to what new log message you are referring
to. The dev_err call is already present in xenbus_va_dev_error, so
everything that's attempted to write to xenstore should also be
printed on the console.

> would be a useful addition for cases *other* than a complete lack of
> any available free page.  Eg, foolishly trying a large kcalloc
> allocation, or some error not related to lack of memory at all.

If there's no real memory shortage a failure to attach a frontend
should result in a message being written to both xenstore and the
console with the current Linux code AFAICT provided
xenbus_dev_{fatal/error} or xenbus_switch_fatal is used.

Thanks, Roger.

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