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Date: Wed, 4 Jul 2018 14:54:25 +0530 From: Ravi Bangoria <ravi.bangoria@...ux.ibm.com> To: Srikar Dronamraju <srikar@...ux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@...hat.com>, rostedt@...dmis.org, mhiramat@...nel.org, peterz@...radead.org, mingo@...hat.com, acme@...nel.org, alexander.shishkin@...ux.intel.com, jolsa@...hat.com, namhyung@...nel.org, linux-kernel@...r.kernel.org, corbet@....net, linux-doc@...r.kernel.org, ananth@...ux.vnet.ibm.com, alexis.berlemont@...il.com, naveen.n.rao@...ux.vnet.ibm.com, linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org, linux@...linux.org.uk, ralf@...ux-mips.org, paul.burton@...s.com, Ravi Bangoria <ravi.bangoria@...ux.ibm.com> Subject: Re: [PATCH v5 06/10] Uprobes: Support SDT markers having reference count (semaphore) Hi Srikar, On 07/04/2018 02:46 PM, Srikar Dronamraju wrote: >> >> I'm not sure if I get your concerns but let me try to explain what happens >> in such cases. please let me know if I misunderstood your point. >> >> 1. Install a probe using perf. >> # ./perf probe sdt_tick:loop2 >> >> >> >> Does this explain your concerns? >> > > > No, this was not my concern. > My concern is with two users on the same USDT. > 1. First user enables the probe point but doesn't increment the ref_cnt. > via uprobe_register > > 2. Second user tries to enable the probe point and also increments the > ref_cnt via uprobe_register_refctr. Ok got it. uprobe_register_refctr() will return with error because we don't allow one uprobe(inode+offset) with multiple reference counter. i.e. If inode+offset matches for two uprobes, ref_ctr_offset must match as well. Patch 8/10 takes care of this. > > 3. If the second user now removes the probe point via uprobe_unregister. > > 4. What is the state of the ref_cnt? > > -- > Thanks and Regards > Srikar >
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