On Tue, 2010-06-22 at 11:19 +0200, Rafael J. Wysocki wrote: > On Tuesday, June 22, 2010, Maxim Levitsky wrote: > > On Mon, 2010-06-21 at 22:26 +0200, Rafael J. Wysocki wrote: > > > On Monday, June 21, 2010, Maxim Levitsky wrote: > > > > On Mon, 2010-06-21 at 23:04 +0300, Adrian Hunter wrote: > > > > > ext Maxim Levitsky wrote: > > > > > > If you don't use CONFIG_MMC_UNSAFE_RESUME, as soon as you attempt to > > > > > > suspend, the card will be removed, therefore this patch doesn't > > > > > > change > > > > > > the behavior of this option. > > > > > > > > > > > > However the removal will be done by pm notifier, which runs while > > > > > > userspace is still not frozen and thus can freely use del_gendisk, > > > > > > without the risk of deadlock which would happen otherwise. > > > > > > > > > > > > > > > > > > Card detect workqueue is now freezeable, > > > > > > therefore if you do use CONFIG_MMC_UNSAFE_RESUME, > > > > > > and remove the card during suspend, the removal will be > > > > > > detected as soon as userspace is unfrozen, again at the moment > > > > > > it is safe to call del_gendisk. > > > > > > > > > > > > Tested with and without CONFIG_MMC_UNSAFE_RESUME with suspend and > > > > > > hibernate. > > > > > > > > > > > > Signed-off-by: Maxim Levitsky <[email protected]> > > > > > > --- > > > > > > drivers/mmc/core/core.c | 54 > > > > > > +++++++++++++++++++++++++++------------------ > > > > > > drivers/mmc/core/host.c | 6 +++++ > > > > > > include/linux/mmc/host.h | 3 ++ > > > > > > 3 files changed, 41 insertions(+), 22 deletions(-) > > > > > > > > > > > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > > > > > > index 569e94d..0cba53a 100644 > > > > > > --- a/drivers/mmc/core/core.c > > > > > > +++ b/drivers/mmc/core/core.c > > > > > > @@ -1259,26 +1259,11 @@ int mmc_suspend_host(struct mmc_host *host) > > > > > > > > > > > > if (host->caps & MMC_CAP_DISABLE) > > > > > > cancel_delayed_work(&host->disable); > > > > > > - cancel_delayed_work(&host->detect); > > > > > > - mmc_flush_scheduled_work(); > > > > > > > > > > > > mmc_bus_get(host); > > > > > > if (host->bus_ops && !host->bus_dead) { > > > > > > if (host->bus_ops->suspend) > > > > > > err = host->bus_ops->suspend(host); > > > > > > - if (err == -ENOSYS || !host->bus_ops->resume) { > > > > > > - /* > > > > > > - * We simply "remove" the card in this case. > > > > > > - * It will be redetected on resume. > > > > > > - */ > > > > > > - if (host->bus_ops->remove) > > > > > > - host->bus_ops->remove(host); > > > > > > - mmc_claim_host(host); > > > > > > - mmc_detach_bus(host); > > > > > > - mmc_release_host(host); > > > > > > - host->pm_flags = 0; > > > > > > - err = 0; > > > > > > - } > > > > > > } > > > > > > mmc_bus_put(host); > > > > > > > > > > > > @@ -1310,12 +1295,6 @@ int mmc_resume_host(struct mmc_host *host) > > > > > > printk(KERN_WARNING "%s: error %d during resume > > > > > > " > > > > > > "(card was removed?)\n", > > > > > > mmc_hostname(host), err); > > > > > > - if (host->bus_ops->remove) > > > > > > - host->bus_ops->remove(host); > > > > > > - mmc_claim_host(host); > > > > > > - mmc_detach_bus(host); > > > > > > - mmc_release_host(host); > > > > > > - /* no need to bother upper layers */ > > > > > > err = 0; > > > > > > } > > > > > > } > > > > > > @@ -1330,6 +1309,37 @@ int mmc_resume_host(struct mmc_host *host) > > > > > > return err; > > > > > > } > > > > > > > > > > > > +/* Do the card removal on suspend if card is assumed removeable > > > > > > + * Do that in pm notifier while userspace isn't yet frozen, so we > > > > > > will be able > > > > > > + to sync the card. > > > > > > +*/ > > > > > > +int mmc_pm_notify(struct notifier_block *notify_block, > > > > > > + unsigned long mode, void > > > > > > *unused) > > > > > > +{ > > > > > > + struct mmc_host *host = container_of( > > > > > > + notify_block, struct mmc_host, pm_notify); > > > > > > + > > > > > > + > > > > > > + switch (mode) { > > > > > > + case PM_HIBERNATION_PREPARE: > > > > > > + case PM_SUSPEND_PREPARE: > > > > > > + > > > > > > + if (!host->bus_ops || host->bus_ops->suspend) > > > > > > + break; > > > > > > + > > > > > > + if (host->bus_ops->remove) > > > > > > + host->bus_ops->remove(host); > > > > > > + mmc_claim_host(host); > > > > > > + mmc_detach_bus(host); > > > > > > + mmc_release_host(host); > > > > > > + host->pm_flags = 0; > > > > > > + break; > > > > > > > > > > Is it possible that you receive PM_SUSPEND_PREPARE > > > > > but there is no suspend and therefore no resume > > > > > and therefore the card is removed but not detected > > > > > again? > > > > This is very good point. > > > > The solution is to kick mmc detection thread from this notifier. > > > > on resume. > > > > I update the patch. > > > > > > > > > > > > > > Is it possible that you are racing with kmmcd and the > > > > > card is added after you receive PM_SUSPEND_PREPARE but > > > > > before kmmcd is frozen? > > > > This is unlikely but valid race. > > > > I afraid I don't know nice way to solve it right now. > > > > I can add some ad-hoc variable to tell interrupt handler not to kick the > > > > detection workqueue after suspend notifier was called. > > > > > > > > I wish there was a generic freeze_workqueue function. > > > > > > There are freezable workqueues that are automatically frozen during > > > suspend > > > by the process freezer. However, at the moment they need to be > > > singlethread > > > and I'm not sure if using one in this particular case is appropriate. > > > > I *do* use freezable work-queue. > > I overlooked that, sorry. > > > However since this is pm notifier, it is called before userspace and the > > workqueue is frozen. > > Therefore I would like manually to freeze the workqueue from the pm > > notifier. > > No, that won't work. You need to find an alternative solution. I guess you > may insert a work item that's going to sleep until a condition is > satisfied (analogous to a workqueue barrier) and wait for it to This screams to be done in generic way. Something like suspend_workqueue() and resume_workqueue();
In addition to that I just found that .suspend function sometimes can return -ENOSYS, which triggers card removal. I wrongly remove that chunk of code. To make the thing picture perfect I would have to invest more time to it, I will do so as soon as I finish my exams. Meanwhile the current patch already fixes all but corner cases or rather nasty hang on suspend with any MMC/SD card inserted. Best regards, Maxim Levitsky -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
