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Subject[PATCH 2/32] mmc: allow host claim / release nesting
From 2d65438fce412a63f09f90fb9af1049c775cbd70 Mon Sep 17 00:00:00 2001
From: Adrian Hunter <adrian.hunter@nokia.com>
Date: Mon, 27 Apr 2009 13:38:42 +0300
Subject: [PATCH] mmc: allow host claim / release nesting

This change allows the MMC host to be claimed in
situations where the host may or may not have
already been claimed. Also 'mmc_try_claim_host()'
is now exported.

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
---
drivers/mmc/core/core.c | 34 +++++++++++++++++++++++++---------
include/linux/mmc/core.h | 1 +
include/linux/mmc/host.h | 2 ++
3 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 41fd127..b262dc6 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -458,16 +458,18 @@ int __mmc_claim_host(struct mmc_host *host, atomic_t *abort)
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
stop = abort ? atomic_read(abort) : 0;
- if (stop || !host->claimed)
+ if (stop || !host->claimed || host->claimer == current)
break;
spin_unlock_irqrestore(&host->lock, flags);
schedule();
spin_lock_irqsave(&host->lock, flags);
}
set_current_state(TASK_RUNNING);
- if (!stop)
+ if (!stop) {
host->claimed = 1;
- else
+ host->claimer = current;
+ host->claim_cnt += 1;
+ } else
wake_up(&host->wq);
spin_unlock_irqrestore(&host->lock, flags);
remove_wait_queue(&host->wq, &wait);
@@ -478,29 +480,43 @@ int __mmc_claim_host(struct mmc_host *host, atomic_t *abort)

EXPORT_SYMBOL(__mmc_claim_host);

-static int mmc_try_claim_host(struct mmc_host *host)
+/**
+ * mmc_try_claim_host - try exclusively to claim a host
+ * @host: mmc host to claim
+ *
+ * Returns %1 if the host is claimed, %0 otherwise.
+ */
+int mmc_try_claim_host(struct mmc_host *host)
{
int claimed_host = 0;
unsigned long flags;

spin_lock_irqsave(&host->lock, flags);
- if (!host->claimed) {
+ if (!host->claimed || host->claimer == current) {
host->claimed = 1;
+ host->claimer = current;
+ host->claim_cnt += 1;
claimed_host = 1;
}
spin_unlock_irqrestore(&host->lock, flags);
return claimed_host;
}
+EXPORT_SYMBOL(mmc_try_claim_host);

static void mmc_do_release_host(struct mmc_host *host)
{
unsigned long flags;

spin_lock_irqsave(&host->lock, flags);
- host->claimed = 0;
- spin_unlock_irqrestore(&host->lock, flags);
-
- wake_up(&host->wq);
+ if (--host->claim_cnt) {
+ /* Release for nested claim */
+ spin_unlock_irqrestore(&host->lock, flags);
+ } else {
+ host->claimed = 0;
+ host->claimer = NULL;
+ spin_unlock_irqrestore(&host->lock, flags);
+ wake_up(&host->wq);
+ }
}

void mmc_host_deeper_disable(struct work_struct *work)
diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
index 7ac8b50..e4898e9 100644
--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h
@@ -139,6 +139,7 @@ extern unsigned int mmc_align_data_size(struct mmc_card *, unsigned int);

extern int __mmc_claim_host(struct mmc_host *host, atomic_t *abort);
extern void mmc_release_host(struct mmc_host *host);
+extern int mmc_try_claim_host(struct mmc_host *host);

/**
* mmc_claim_host - exclusively claim a host
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 583c068..9cc5be9 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -182,6 +182,8 @@ struct mmc_host {
struct mmc_card *card; /* device attached to this host */

wait_queue_head_t wq;
+ struct task_struct *claimer; /* task that has host claimed */
+ int claim_cnt; /* "claim" nesting count */

struct delayed_work detect;

--
1.5.6.3


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