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Date: Mon, 22 Jun 2015 09:30:20 +0200 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Geert Uytterhoeven <geert+renesas@...der.be> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>, Thomas Gleixner <tglx@...utronix.de>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Kevin Hilman <khilman@...nel.org>, Ulf Hansson <ulf.hansson@...aro.org>, Magnus Damm <damm@...nsource.se>, Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, Linux PM list <linux-pm@...r.kernel.org>, Linux-sh list <linux-sh@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code On Thu, Jun 18, 2015 at 12:22 PM, Geert Uytterhoeven <geert+renesas@...der.be> wrote: > If pm_genpd_{add,remove}_device() keeps on failing with -EAGAIN, we end > up with an infinite loop in genpd_dev_pm_{at,de}tach(). > > This may happen due to a genpd.prepared_count imbalance. This is a bug > elsewhere, but it will result in a system lock up, possibly during > reboot of an otherwise functioning system. > > To avoid this, put a limit on the maximum number of loop iterations, > including a simple back-off mechanism. If the limit is reached, the > operation will just fail. An error message is already printed. > > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be> > --- > drivers/base/power/domain.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c > index cdd547bd67df8218..aa06f60b98b8af35 100644 > --- a/drivers/base/power/domain.c > +++ b/drivers/base/power/domain.c > @@ -2218,10 +2226,13 @@ int genpd_dev_pm_attach(struct device *dev) > > dev_dbg(dev, "adding to PM domain %s\n", pd->name); > > - while (1) { > + for (i = 0; i < GENPD_RETRIES; i++) { Sorry, there's a declaration of "i" missing. > ret = pm_genpd_add_device(pd, dev); > if (ret != -EAGAIN) > break; > + > + if (i > GENPD_RETRIES / 2) > + udelay(GENPD_DELAY_US); > cond_resched(); > } > > -- > 1.9.1 Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/
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