> -----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? 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/ -- 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
