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Date: Fri, 15 Apr 2011 16:22:19 +0200
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Subject: Re: [Qemu-devel] [PATCH 2/2] add tracing of scsi requests
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: qemu-devel@nongnu.org

On 04/15/2011 04:15 PM, Stefan Hajnoczi wrote:
> On Fri, Apr 15, 2011 at 2:24 PM, Paolo Bonzini<pbonzini@redhat.com>  wrote:
>> +disable scsi_req_parsed(int target, int lun, int tag, int cmd, const char *cmdname, int mode, int xfer, uint64_t lba) "target %d lun %d tag %d command %d (%s) dir %d length %d lba %"PRIu64""
>
> Tracing strings isn't possible with all trace backends, so we should
> avoid it.  It works fine with stderr but other trace backends may not
> be in the same address space (they are unable to dereference pointers
> to strings) or simply not have the ability to record variable-length
> data.

Yeah, I saw them.  What happens with the other backends?  Do they crash 
or do they just record bogus data?  If the latter (like IIRC 
simpletrace), I'd really like to keep the string.  It is duplicating the 
cmd argument, so it is possible to work without it on non-stderr 
backends; with stderr OTOH the human-readable version is really useful 
before you have learnt the SCSI spec by heart. :)

Paolo