Date: Sat, 12 May 2012 17:37:54 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Xin LI <delphij@gmail.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Xin LI <delphij@freebsd.org> Subject: Re: svn commit: r235301 - head/sys/kern Message-ID: <20120512172928.U926@besplex.bde.org> In-Reply-To: <CAGMYy3twRfACSF9rMCwjJOwUBuT_j9N1VLtTeJ5xNO6xhnd2PA@mail.gmail.com> References: <201205112343.q4BNhWh7005829@svn.freebsd.org> <CAGMYy3twRfACSF9rMCwjJOwUBuT_j9N1VLtTeJ5xNO6xhnd2PA@mail.gmail.com>
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On Fri, 11 May 2012, Xin LI wrote: >> Log: >> Revert previous revision, misunderstood the code :( >> >> Modified: >> head/sys/kern/kern_kthread.c >> >> Modified: head/sys/kern/kern_kthread.c >> ============================================================================== >> --- head/sys/kern/kern_kthread.c Fri May 11 23:41:52 2012 (r235300) >> +++ head/sys/kern/kern_kthread.c Fri May 11 23:43:32 2012 (r235301) >> @@ -182,7 +182,6 @@ kproc_suspend(struct proc *p, int timo) >> return (EINVAL); >> } >> SIGADDSET(p->p_siglist, SIGSTOP); >> - PROC_UNLOCK(p); >> wakeup(p); >> return msleep(&p->p_siglist, &p->p_mtx, PPAUSE | PDROP, "suspkp", timo); Please don't use mailer clients that corrupt whitespace to binary characters. The above is unreadable in vi (but i remember it from the original). > For the record, p->p_mtx is the mutex used by PROC_[UN]LOCK(), which > has to be held while calling msleep(). Even if it weren't, dropping the lock before sleeping would give a classic race. Otherwise, PROC_UNLOCK() is a good obfuscation. p_mtx in the sleep call isn't similarly obfuscated. Some subsystems have a macro that obfuscates the name of their lock(s) too, but proc.h doesn't. kern/*.c has 23 hard-coded references of the form &somep->p_mtx. Bruce
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