[tip:locking/urgent] i2c/mux, locking/core: Annotate the nested rt_mutex usage
From: tip-bot for Peter Rosin
Date: Wed Jul 25 2018 - 10:20:09 EST
Commit-ID: 7b94ea50514d1a0dc94f02723b603c27bc0ea597
Gitweb: https://git.kernel.org/tip/7b94ea50514d1a0dc94f02723b603c27bc0ea597
Author: Peter Rosin <peda@xxxxxxxxxx>
AuthorDate: Fri, 20 Jul 2018 10:39:14 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 25 Jul 2018 11:22:20 +0200
i2c/mux, locking/core: Annotate the nested rt_mutex usage
If an i2c topology has instances of nested muxes, then a lockdep splat
is produced when when i2c_parent_lock_bus() is called. Here is an
example:
============================================
WARNING: possible recursive locking detected
--------------------------------------------
insmod/68159 is trying to acquire lock:
(i2c_register_adapter#2){+.+.}, at: i2c_parent_lock_bus+0x32/0x50 [i2c_mux]
but task is already holding lock:
(i2c_register_adapter#2){+.+.}, at: i2c_parent_lock_bus+0x32/0x50 [i2c_mux]
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(i2c_register_adapter#2);
lock(i2c_register_adapter#2);
*** DEADLOCK ***
May be due to missing lock nesting notation
1 lock held by insmod/68159:
#0: (i2c_register_adapter#2){+.+.}, at: i2c_parent_lock_bus+0x32/0x50 [i2c_mux]
stack backtrace:
CPU: 13 PID: 68159 Comm: insmod Tainted: G O
Call Trace:
dump_stack+0x67/0x98
__lock_acquire+0x162e/0x1780
lock_acquire+0xba/0x200
rt_mutex_lock+0x44/0x60
i2c_parent_lock_bus+0x32/0x50 [i2c_mux]
i2c_parent_lock_bus+0x3e/0x50 [i2c_mux]
i2c_smbus_xfer+0xf0/0x700
i2c_smbus_read_byte+0x42/0x70
my2c_init+0xa2/0x1000 [my2c]
do_one_initcall+0x51/0x192
do_init_module+0x62/0x216
load_module+0x20f9/0x2b50
SYSC_init_module+0x19a/0x1c0
SyS_init_module+0xe/0x10
do_syscall_64+0x6c/0x1a0
entry_SYSCALL_64_after_hwframe+0x42/0xb7
Reported-by: John Sperbeck <jsperbeck@xxxxxxxxxx>
Tested-by: John Sperbeck <jsperbeck@xxxxxxxxxx>
Signed-off-by: Peter Rosin <peda@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Deepa Dinamani <deepadinamani@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Chang <dpf@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Philippe Ombredanne <pombredanne@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20180720083914.1950-3-peda@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
drivers/i2c/i2c-core-base.c | 2 +-
drivers/i2c/i2c-mux.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 301285c54603..15c95aaa484c 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -624,7 +624,7 @@ static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
static void i2c_adapter_lock_bus(struct i2c_adapter *adapter,
unsigned int flags)
{
- rt_mutex_lock(&adapter->bus_lock);
+ rt_mutex_lock_nested(&adapter->bus_lock, i2c_adapter_depth(adapter));
}
/**
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 300ab4b672e4..29646aa6132e 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -144,7 +144,7 @@ static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
struct i2c_mux_priv *priv = adapter->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
- rt_mutex_lock(&parent->mux_lock);
+ rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
if (!(flags & I2C_LOCK_ROOT_ADAPTER))
return;
i2c_lock_bus(parent, flags);
@@ -181,7 +181,7 @@ static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
struct i2c_mux_priv *priv = adapter->algo_data;
struct i2c_adapter *parent = priv->muxc->parent;
- rt_mutex_lock(&parent->mux_lock);
+ rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
i2c_lock_bus(parent, flags);
}