Date: Wed, 1 Nov 2006 10:21:09 -0500 From: John Baldwin <jhb@freebsd.org> To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: cvs-src@freebsd.org, John Birrell <jb@freebsd.org>, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/amd64/amd64 genassym.c src/sys/arm/arm genassym.c src/sys/i386/i386 genassym.c src/sys/ia64/ia64 genassym.c src/sys/kern subr_prf.c tty_cons.c src/sys/powerpc/powerpc genassym.c src/sys/sparc64/sparc64 ... Message-ID: <200611011021.10535.jhb@freebsd.org> In-Reply-To: <20061101093550.GK15861@garage.freebsd.pl> References: <200611010454.kA14spYn014613@repoman.freebsd.org> <20061101093550.GK15861@garage.freebsd.pl>
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On Wednesday 01 November 2006 04:35, Pawel Jakub Dawidek wrote:
> On Wed, Nov 01, 2006 at 04:54:51AM +0000, John Birrell wrote:
> > jb 2006-11-01 04:54:51 UTC
> >
> > FreeBSD src repository
> >
> > Modified files:
> > sys/amd64/amd64 genassym.c
> > sys/arm/arm genassym.c
> > sys/i386/i386 genassym.c
> > sys/ia64/ia64 genassym.c
> > sys/kern subr_prf.c tty_cons.c
> > sys/powerpc/powerpc genassym.c
> > sys/sparc64/sparc64 genassym.c
> > sys/sys cons.h pcpu.h
> > Log:
> > Add a cnputs() function to write a string to the console with
> > a lock to prevent interspersed strings written from different CPUs
> > at the same time.
>
> Nice, this was very annoying, but I'd still like to have a recursive
> lock, which could be used by printf(9) consumers. For example, I'm not
> able to implement such macro in a way that ensure everything will be
> printed in one line:
>
> #define G_MIRROR_DEBUG(lvl, ...) do { \
> if (g_mirror_debug >= (lvl)) { \
> printf("GEOM_MIRROR"); \
> if (g_mirror_debug > 0) \
> printf("[%u]", lvl); \
> printf(": "); \
> printf(__VA_ARGS__); \
> printf("\n"); \
> } \
> } while (0)
>
> What I'd like is a global printf_lock which will allow me to put many
> separate printfs under it and be sure it won't be messed up by other
> CPUs. Having it recursive could also eliminate the need for per-CPU
> buffers, as I don't think we care about performance here.
>
> What do you think?
Because printf is used for things like panics, I think it needs to be as
robust as possible. I think adding a larger lock like you request would make
it too fragile.
--
John Baldwin
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