On Wed, 11 May 2011, Dong, Chuanxiao wrote: > > > -----Original Message----- > > From: Guennadi Liakhovetski [mailto:g.liakhovetski@xxxxxx] > > Sent: Wednesday, May 11, 2011 8:26 PM > > To: Dong, Chuanxiao > > Cc: linux-mmc@xxxxxxxxxxxxxxx > > Subject: RE: [PATCH] MMC: fix a race between card-detect rescan and clock-gate > > work instances > > > > Hi > > > > On Wed, 11 May 2011, Dong, Chuanxiao wrote: > > > > > Hello Liakhovetski, > > > > > > Right now I am facing some problem during kernel booting which indicate > > > caused by MMC driver. So I think I encountered the race condition you > > > mentioned below. > > > > Which kernel are you using? With my patch or without it? What makes you > > think, that your problem is caused by a race in MMC? Races rarely occur > > reproducibly, so, it seems a bit unlikely to me during the boot process. > I am using the kernel without your patch, so you can say my kernel is > before your patch. > After applied your patch, I never encountered booting failure. So this > makes me think I encountered the race condition between card-detect > rescan and clock-gate thread. > > But I am not quiet understanding what race it is actually. Can you just > introduce what race you faced? Is this race condition caused by > sdhci_set_ios reenter or something else? Look here for an explanation: http://thread.gmane.org/gmane.linux.kernel.mmc/7253 Thanks Guennadi > > Thanks > Chuanxiao > > > > > I have gone through MMC stack code, seems sdhci_set_ios already wrapped > > > by spin lock/unlock, so I am a little not understanding why there is > > > still a race condition? > > > > Again, are you referring to the kernel before my patch or after? > > > > Thanks > > Guennadi > > > > > Is this race condition caused by sdhci_set_ios function reenter or > > > something else? > > > > > > Thanks for your help on this. > > > > > > BR > > > Chuanxiao > > > -----Original Message----- > > > From: linux-mmc-owner@xxxxxxxxxxxxxxx > > [mailto:linux-mmc-owner@xxxxxxxxxxxxxxx] On Behalf Of Guennadi Liakhovetski > > > Sent: Saturday, April 16, 2011 2:08 AM > > > To: linux-sh@xxxxxxxxxxxxxxx > > > Cc: linux-mmc@xxxxxxxxxxxxxxx; Magnus Damm; Simon Horman; Linus Walleij > > > Subject: [PATCH] MMC: fix a race between card-detect rescan and clock-gate > > work instances > > > > > > Currently there is a race in the MMC core between a card-detect > > > rescan work and the clock-gating work, scheduled from a command > > > completion. Fix it by removing the dedicated clock-gating mutex and > > > using the MMC standard locking mechanism instead. > > > > > > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx> > > > Cc: Simon Horman <horms@xxxxxxxxxxxx> > > > Cc: Magnus Damm <damm@xxxxxxxxxxxxx> > > > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx> > > > --- > > > drivers/mmc/core/host.c | 9 ++++----- > > > include/linux/mmc/host.h | 1 - > > > 2 files changed, 4 insertions(+), 6 deletions(-) > > > > > > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c > > > index 461e6a1..2b200c1 100644 > > > --- a/drivers/mmc/core/host.c > > > +++ b/drivers/mmc/core/host.c > > > @@ -94,7 +94,7 @@ static void mmc_host_clk_gate_delayed(struct mmc_host > > *host) > > > spin_unlock_irqrestore(&host->clk_lock, flags); > > > return; > > > } > > > - mutex_lock(&host->clk_gate_mutex); > > > + mmc_claim_host(host); > > > spin_lock_irqsave(&host->clk_lock, flags); > > > if (!host->clk_requests) { > > > spin_unlock_irqrestore(&host->clk_lock, flags); > > > @@ -104,7 +104,7 @@ static void mmc_host_clk_gate_delayed(struct > > mmc_host *host) > > > pr_debug("%s: gated MCI clock\n", mmc_hostname(host)); > > > } > > > spin_unlock_irqrestore(&host->clk_lock, flags); > > > - mutex_unlock(&host->clk_gate_mutex); > > > + mmc_release_host(host); > > > } > > > > > > /* > > > @@ -130,7 +130,7 @@ void mmc_host_clk_ungate(struct mmc_host *host) > > > { > > > unsigned long flags; > > > > > > - mutex_lock(&host->clk_gate_mutex); > > > + mmc_claim_host(host); > > > spin_lock_irqsave(&host->clk_lock, flags); > > > if (host->clk_gated) { > > > spin_unlock_irqrestore(&host->clk_lock, flags); > > > @@ -140,7 +140,7 @@ void mmc_host_clk_ungate(struct mmc_host *host) > > > } > > > host->clk_requests++; > > > spin_unlock_irqrestore(&host->clk_lock, flags); > > > - mutex_unlock(&host->clk_gate_mutex); > > > + mmc_release_host(host); > > > } > > > > > > /** > > > @@ -215,7 +215,6 @@ static inline void mmc_host_clk_init(struct mmc_host > > *host) > > > host->clk_gated = false; > > > INIT_WORK(&host->clk_gate_work, mmc_host_clk_gate_work); > > > spin_lock_init(&host->clk_lock); > > > - mutex_init(&host->clk_gate_mutex); > > > } > > > > > > /** > > > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h > > > index bcb793e..eb792cb 100644 > > > --- a/include/linux/mmc/host.h > > > +++ b/include/linux/mmc/host.h > > > @@ -183,7 +183,6 @@ struct mmc_host { > > > struct work_struct clk_gate_work; /* delayed clock gate */ > > > unsigned int clk_old; /* old clock value cache */ > > > spinlock_t clk_lock; /* lock for clk fields */ > > > - struct mutex clk_gate_mutex; /* mutex for clock gating */ > > > #endif > > > > > > /* host specific block data */ > > > -- > > > 1.7.2.5 > > > > > > -- > > > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > > --- > > Guennadi Liakhovetski, Ph.D. > > Freelance Open-Source Software Developer > > http://www.open-technology.de/ > --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
