Hi Chris, > -----Original Message----- > From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc- > owner@xxxxxxxxxxxxxxx] On Behalf Of Chris Ball > Sent: Wednesday, January 04, 2012 8:07 PM > To: Guennadi Liakhovetski > Cc: linux-mmc@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] mmc: fix a deadlock between system suspend and MMC > block IO > > Hi, > > On Wed, Jan 04 2012, Guennadi Liakhovetski wrote: > > Performing MMC block IO with simultaneous STR can lead to a deadlock: > the > > mmc_pm_notify() function claims the host and then calls bus .remove() > > method, which lands in mmc_blk_remove(), which calls > mmc_blk_remove_req() > > then it goes to -> mmc_cleanup_queue() -> kthread_stop(), which waits > for > > the mmc-block thread to stop. If the mmc-block thread at that time is > > processing block requests, it will also try to claim the host in > > mmc_blk_issue_rq() and block there. This patch fixes the problem by > > calling .remove() before claiming the host. > > > > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx> > > --- > > drivers/mmc/core/core.c | 4 ++-- > > 1 files changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c > > index a2aa860..a68f085 100644 > > --- a/drivers/mmc/core/core.c > > +++ b/drivers/mmc/core/core.c > > @@ -2476,11 +2476,11 @@ int mmc_pm_notify(struct notifier_block > *notify_block, > > if (!host->bus_ops || host->bus_ops->suspend) > > break; > > > > - mmc_claim_host(host); > > - > > + /* On 2 occasions above bus_ops->remove() is called > unlocked */ > > if (host->bus_ops->remove) > > host->bus_ops->remove(host); > > > > + mmc_claim_host(host); > > mmc_detach_bus(host); > > mmc_power_off(host); > > mmc_release_host(host); > > Thanks. The commit message explanation is very good, but the comment > is > a bit cryptic. Shall we make it longer? I think even just: > > /* Calling bus_ops->remove() with a claimed host can deadlock */ > > would be better. This patch will actually fix a long standing issue for most of us. But if I remember correctly, Andrei had some comments on the same patch some time back. Would it be good to include him for comments? Thanks, Arindam > > - Chris. > -- > Chris Ball <cjb@xxxxxxxxxx> <http://printf.net/> > One Laptop Per Child > -- > 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 -- 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
