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McKenney" Cc: Luis Chamberlain , shinichiro.kawasaki@wdc.com, Klaus Jensen , linux-block@vger.kernel.org, Pankaj Raghav , Pankaj Raghav , Adam Manzanares Subject: Re: blktests with zbd/006 ZNS triggers a possible false positive RCU stall Message-ID: <20220415043021.awhfncjjt22vyajg@offworld> References: <20220415010945.wvyztmss7rfqnlog@offworld> <20220415035438.GE4285@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20220415035438.GE4285@paulmck-ThinkPad-P17-Gen-1> User-Agent: NeoMutt/20201120 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, 14 Apr 2022, Paul E. McKenney wrote: >On Thu, Apr 14, 2022 at 06:09:45PM -0700, Davidlohr Bueso wrote: >> No idea, however, why this would happen when using qemu as opposed to >> nbd. > >This one is a bit strange, no two ways about it. > >In theory, vCPU preemption is a possibility. In practice, if the >RCU grace-period kthread's vCPU was preempted for so long, I would >have expected the RCU CPU stall warning to complain about starvation. >But it still might be worth tracing context switches on the underlying >hypervisor. Right, but both cases are VMs which is what throws me off, regardless of the zns drive. Or is this not the case, Luis? Thanks, Davidlohr