Date: Sat, 1 May 2010 16:49:25 +0200 From: Attilio Rao <attilio@freebsd.org> To: Kip Macy <kmacy@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r207460 - head/sys/vm Message-ID: <AANLkTik_LSQGaAs5owwIQRXZt_NRRQ6ND_VJVm-cP9oz@mail.gmail.com> In-Reply-To: <201005010341.o413fMhP067068@svn.freebsd.org> References: <201005010341.o413fMhP067068@svn.freebsd.org>
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2010/5/1 Kip Macy <kmacy@freebsd.org>: > Author: kmacy > Date: Sat May 1 03:41:21 2010 > New Revision: 207460 > URL: http://svn.freebsd.org/changeset/base/207460 > > Log: > Update locking comment above vm_page: > - re-assign page queue lock "Q" > - assign page lock "P" > - update several uncommented fields > - observe that hold_count is now protected by the page lock "P" > > Modified: > head/sys/vm/vm_page.h > > Modified: head/sys/vm/vm_page.h > ============================================================================== > --- head/sys/vm/vm_page.h Sat May 1 02:53:43 2010 (r207459) > +++ head/sys/vm/vm_page.h Sat May 1 03:41:21 2010 (r207460) > @@ -90,20 +90,21 @@ > * and sundry status bits. > * > * Fields in this structure are locked either by the lock on the > - * object that the page belongs to (O) or by the lock on the page > - * queues (P). > + * object that the page belongs to (O), its corresponding page lock (P), > + * or by the lock on the page queues (Q). > + * > */ > > TAILQ_HEAD(pglist, vm_page); > > struct vm_page { > - TAILQ_ENTRY(vm_page) pageq; /* queue info for FIFO queue or free list (P) */ > + TAILQ_ENTRY(vm_page) pageq; /* queue info for FIFO queue or free list (Q) */ > TAILQ_ENTRY(vm_page) listq; /* pages in same object (O) */ > struct vm_page *left; /* splay tree link (O) */ > struct vm_page *right; /* splay tree link (O) */ > > - vm_object_t object; /* which object am I in (O,P)*/ > - vm_pindex_t pindex; /* offset into object (O,P) */ > + vm_object_t object; /* which object am I in (O,Q)*/ > + vm_pindex_t pindex; /* offset into object (O,Q) */ This notation is ambigous. It doesn't let understand if the lock may be held both together or not, which rules happen for reading/writing such values, etc. May you please follow well-known patterns like the tables in subr_turnstile.c ? (+ for both of them, / for one of them, clarify if it is safe to read them with just one lock of them held, etc). Attilio -- Peace can only be achieved by understanding - A. Einstein
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