Date: Wed, 11 Mar 2009 16:38:39 +0300 From: pluknet <pluknet@gmail.com> To: freebsd-hackers@freebsd.org Subject: Non-existing p_vmspace. When is it possible? Message-ID: <a31046fc0903110638x52d9b6cbt4d39656c0be61442@mail.gmail.com> In-Reply-To: <a31046fc0903110606r7c398ef1ud2921e7c30658fe6@mail.gmail.com> References: <a31046fc0903110606r7c398ef1ud2921e7c30658fe6@mail.gmail.com>
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Hi. I perform in FOREACH_PROC_IN_SYSTEM(), where I conditionally look at p_vmspace internals. I'd like to know the safe way to reference p_vmspace fields without potential null-dereference. I see an example in vm_pageout_oom(), where making access to p->p_vmspace fields is done without additional checks. Nevertheless I want to further catch on how it works. Currently I additionally explicitly check on P_SYSTEM and PRS_NEW, then p->p_vmspace against NULL. So I'd wish to understand if a time-window between 1) placing a new process to proclist =A0and 2) attaching vmspace to this process is possible at all, and then in what cases. I see in fork1() that a new process' (named p2 here) state is set to PRS_NEW just before LIST_INSERT_HEAD(&allproc, p2, p_list) and then (after vmspace is already attached in vm_forkproc()) is set to PRS_NORMAL. So an additional check on p_vmspace !=3D NULL is not need. Am I right? Thanks. --=20 wbr, pluknet
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