Hi all,
I encountered a dead lock issue. Two threads try to claim host, unfortunately
one thread needs to sync with the other. I encountered this issue with SD
card when testing system entering S3. Does anybody encounter the same issue?
Environment:
1. without CONFIG_MMC_UNSAFE_RESUME operation
2. the SD card mounted
During system tried to enter S3, mmc_pm_notifier will be called first to remove
SD card. So calling sequence in SD remove thread is like this:
mmc_claim_host
bus_ops->remove
....
....
mmc_cleanup_queue
kthread_stop(mq->thread)
...
...
Mean while, mmc_cleanup_queue wakes up mq->thread, the calling sequence in
mq->thread is
like this:
mmc_queue_thread
mq->issue_fn (mmc_blk_issue_rq)
mmc_claim_host (dead lock)
....
....
Since mmc_claim_host is called in mq->thread (not SD remove thread) again,
unfortunately right now host is already claimed by SD remove thread which is
also waiting for mq->thread finished, so cause a dead lock here.
Move the mmc_claim_host(in mmc_pm_notifier) after bus_ops->remove can resolve
this dead lock. mmc_suspend_host() is using the same way to claim host.
Need to know your suggestions.
Signed-off-by: He Bo <[email protected]>
Signed-off-by: Chuanxiao Dong <[email protected]>
---
drivers/mmc/core/core.c | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 68091dd..1e27588 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1850,11 +1850,10 @@ int mmc_pm_notify(struct notifier_block *notify_block,
if (!host->bus_ops || host->bus_ops->suspend)
break;
- mmc_claim_host(host);
-
if (host->bus_ops->remove)
host->bus_ops->remove(host);
+ mmc_claim_host(host);
mmc_detach_bus(host);
mmc_release_host(host);
host->pm_flags = 0;
--
1.7.3.4
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