Date: Sun, 20 Feb 2005 10:29:16 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: PeterJeremy@optushome.com.au Cc: freebsd-hackers@freebsd.org Subject: Re: Signalling a process from a INTR_FAST handler Message-ID: <20050220.102916.39467732.imp@bsdimp.com> In-Reply-To: <20050220054251.GB28983@cirb503493.alcatel.com.au> References: <20050220054251.GB28983@cirb503493.alcatel.com.au>
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In message: <20050220054251.GB28983@cirb503493.alcatel.com.au>
Peter Jeremy <PeterJeremy@optushome.com.au> writes:
: I have a hardware interrupt handler that has to forward a signal to
: userland and that I'd like to mark INTR_FAST. AFAIK, the normal way
: to forward a signal is:
: if ((p = pfind(sc->pid_to_signal)) != NULL) {
: psignal(p, SIGUSR2);
: PROC_UNLOCK(p);
: }
:
: But pfind(9) does a PROC_LOCK() which implies it can sleep and therefore
: can't be used by an INTR_FAST handler.
:
: Firstly, am I correct? If so, is there an alternative approach I can use?
I've been storing td->td_proc in my softc and using that to signal the
process. However, I don't know if you can call psignal without the
process being locked... Hmmm, the big 'PROC_LOCK_ASSERT()' says that
you can't. And the routines that psignal calls also do the
PROC_LOCK_ASSERT... You may be stuck using some kind of helper
mechanism to accomplish this (wakeup another thread and send the
signal from there, there are many variations on this theme).
Warner
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