Hi Chris, > -----Original Message----- > From: Chris Ball [mailto:cjb@xxxxxxxxxx] > Sent: Wednesday, January 04, 2012 8:34 PM > To: Nath, Arindam > Cc: Guennadi Liakhovetski; linux-mmc@xxxxxxxxxxxxxxx; Andrei Warkentin > Subject: Re: [PATCH] mmc: fix a deadlock between system suspend and MMC > block IO > > Hi, > > Adding Andrei to CC. Thanks, > > - Chris. > > On Wed, Jan 04 2012, Nath, Arindam wrote: > > 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? I think we can push this patch now. If someone has any objections, we can discuss later. Acked-by: Arindam Nath <arindam.nath@xxxxxxx> Thanks, Arindam > > -- > 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
