From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mika Kuoppala Subject: [PATCH 1/1] i2c: Prevent priority inversion on top of bus lock Date: Wed, 16 Sep 2009 14:17:09 +0300 Message-ID: <1253099829-17655-2-git-send-email-mika.kuoppala@nokia.com> References: <1253099829-17655-1-git-send-email-mika.kuoppala@nokia.com> Return-path: In-Reply-To: <1253099829-17655-1-git-send-email-mika.kuoppala-xNZwKgViW5gAvxtiuMwx3w@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org Cc: ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mika Kuoppala List-Id: linux-i2c@vger.kernel.org Low priority thread holding the i2c bus mutex could block more high priority threads to access the bus resulting in unacceptable latencies. Change the mutex type to rt_mutex preventing priority inversion. Tested-by: Peter Ujfalusi Signed-off-by: Mika Kuoppala --- drivers/i2c/i2c-core.c | 12 ++++++------ include/linux/i2c.h | 3 +-- 2 files changed, 7 insertions(+), 8 deletions(-) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index 0e45c29..40f645f 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -548,7 +548,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap) goto out_list; } - mutex_init(&adap->bus_lock); + rt_mutex_init(&adap->bus_lock); /* Set default timeout to 1 second if not already set */ if (adap->timeout == 0) @@ -1018,12 +1018,12 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) #endif if (in_atomic() || irqs_disabled()) { - ret = mutex_trylock(&adap->bus_lock); + ret = rt_mutex_trylock(&adap->bus_lock); if (!ret) /* I2C activity is ongoing. */ return -EAGAIN; } else { - mutex_lock_nested(&adap->bus_lock, adap->level); + rt_mutex_lock(&adap->bus_lock); } /* Retry automatically on arbitration loss */ @@ -1035,7 +1035,7 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) if (time_after(jiffies, orig_jiffies + adap->timeout)) break; } - mutex_unlock(&adap->bus_lock); + rt_mutex_unlock(&adap->bus_lock); return ret; } else { @@ -1839,7 +1839,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags, flags &= I2C_M_TEN | I2C_CLIENT_PEC; if (adapter->algo->smbus_xfer) { - mutex_lock(&adapter->bus_lock); + rt_mutex_lock(&adapter->bus_lock); /* Retry automatically on arbitration loss */ orig_jiffies = jiffies; @@ -1853,7 +1853,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags, orig_jiffies + adapter->timeout)) break; } - mutex_unlock(&adapter->bus_lock); + rt_mutex_unlock(&adapter->bus_lock); } else res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write, command, protocol, data); diff --git a/include/linux/i2c.h b/include/linux/i2c.h index f4784c0..ddca85d 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -340,8 +340,7 @@ struct i2c_adapter { void *algo_data; /* data fields that are valid for all devices */ - u8 level; /* nesting level for lockdep */ - struct mutex bus_lock; + struct rt_mutex bus_lock; int timeout; /* in jiffies */ int retries; -- 1.6.5.rc0