Date: Wed, 20 Dec 2006 13:41:15 +0100 From: "Attilio Rao" <attilio@freebsd.org> To: "Martin Blapp" <mb@imp.ch> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/kern tty.c Message-ID: <3bbf2fe10612200441i2f658b59i83de7c21c7290ab1@mail.gmail.com> In-Reply-To: <20061220120419.M53548@godot.imp.ch> References: <200612192234.kBJMYYo0055529@repoman.freebsd.org> <3bbf2fe10612191850y3a546fcew486575385b1400df@mail.gmail.com> <20061220120419.M53548@godot.imp.ch>
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2006/12/20, Martin Blapp <mb@imp.ch>: > > Hi, > > > Since proctree_lock is a sx lock which uses 2 condition variables, > > they alredy drop Giant (DROP_GIANT()) before sleeping. Are you secure > > it is the right thing to do here? > > Yes I am. > > sx_slock() can call cv_wait() which later can call cv_wait_unlock ... > if there is already a lock we need to share ... After a possible > sleep cv_wait_unlock looks like: > > cv_wait_unlock(struct cv *cvp, struct mtx *mp) > > [...] > sleepq_lock(cvp); > > cvp->cv_waiters++; > DROP_GIANT(); > mtx_unlock(mp); > > [...] > > It can call DROP_GIANT for a short amount of time. This was the race. No, it drops Giant for all the time it sleeps. Maybe the race is somewhere else. Attilio -- Peace can only be achieved by understanding - A. Einstein
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