Date: Thu, 13 Oct 2011 08:35:09 -0400 From: Haozhong Zhang <snowzh8512@gmail.com> To: freebsd-hackers@freebsd.org Subject: question about the exchanges of td->td_lock and mtx in sched_switch() of sched_ule Message-ID: <CAK6mpvpzg_8=kRvCPuH0%2Bn%2BFbfwzJUEtRVSjVi-DSNe%2BLaW46Q@mail.gmail.com>
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Hi, I'm recently reading the code of sched_ule in freebsd 8.2.0 and have two questions. 1. sched_switch() (in sched_ule.c) invokes cpu_switch() (at line 1852) and thread_unblock_switch() (at line 1867). These two functions exchange td->td_lock and mtx. What are the purposes of these exchanges? 2. Can the exchange in cpu_switch() (in amd64/amd64/cpu_switch.S, at line 134) be done before calling cpu_switch()? I mean, does this reorder of exchange and other operations in cpu_switch() cause side-effects to other code? Thank you! - Haozhong Zhang
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