Date: Sat, 10 Jan 2004 15:08:22 +0100 From: "Daan Vreeken [PA4DAN]" <Danovitsch@Vitsch.net> To: FreeBSD-hackers@FreeBSD.org Subject: kernel threads and printf locking question Message-ID: <200401101508.22640.Danovitsch@Vitsch.net>
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Hi, I am writing a kernel module in which I have created a kernel thread with= =20 kthread_create. For debugging I have added a couple of printf's in the=20 thread-routine. Running the module on a single-proc system works fine, bu= t=20 when running it on one of my SMP machines the console freezes after a cou= ple=20 of seconds. I have been looking through the archives and through some other drivers (= for=20 example randomdev.c uses a kthread and printf's from it ). I found a vers= ion=20 of randomdev.c with google that lock's Giant while calling printf, but=20 randomdev.c in my src-tree has no locking there. (I'm using 5.1-RELEASE) Right now I have changed all printf's in my module into a macro-function = that=20 checks if ( curproc =3D=3D our thread ) and locks Giant if true, then pri= ntf's.=20 (since some of the routines get called both from the thread and from othe= r=20 places.) What is the current state of printf-locking when called from a kernel thr= ead?=20 Is locking Giant the only possible way to avoid problems on SMP systems, = or=20 is there a more fine-grained printf lock available? (on 5.1-RELEASE or=20 -current) thanks, Daan
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