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? -- 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
