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Date: Fri, 29 Jun 2018 08:53:28 +0530 From: Ravi Bangoria <ravi.bangoria@...ux.ibm.com> To: Oleg Nesterov <oleg@...hat.com> Cc: srikar@...ux.vnet.ibm.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 Oleg, On 06/29/2018 01:21 AM, Oleg Nesterov wrote: > I have to admit that after a quick glance I can't understand this patch > at all... I'll try to read it again tomorrow, but could you at least explain > how find_node_in_range/build_probe_list can work if off_type==REF_CTR_OFFSET? > > On 06/28, Ravi Bangoria wrote: >> >> -find_node_in_range(struct inode *inode, loff_t min, loff_t max) >> +find_node_in_range(struct inode *inode, int off_type, loff_t min, loff_t max) >> { >> struct rb_node *n = uprobes_tree.rb_node; >> >> while (n) { >> struct uprobe *u = rb_entry(n, struct uprobe, rb_node); >> + loff_t offset = uprobe_get_offset(u, off_type); >> >> if (inode < u->inode) { >> n = n->rb_left; >> } else if (inode > u->inode) { >> n = n->rb_right; >> } else { >> - if (max < u->offset) >> + if (max < offset) >> n = n->rb_left; >> - else if (min > u->offset) >> + else if (min > offset) >> n = n->rb_right; >> else >> break; > > To simplify, lets forget about uprobe->inode (which acts as a key too). So uprobes_tree > is a binary tree sorted by uprobe->offset key and that is why the binary search works. > > But it is not sorted by uprobe->ref_ctr_offset. So for example n->rb_left can have the > n->ref_ctr_offset key that is greater than the n's ref_ctr_offset. So how we can use the > binary search if REF_CTR_OFFSET? > > I must have missed something, I assume you tested this patch and it works somehow... > Right, I've misinterpreted that code. Will check it. Thanks for explaining, Ravi
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