| From foo@baz Sun Aug 26 09:13:00 CEST 2018 |
| From: Peter Rosin <peda@axentia.se> |
| Date: Fri, 20 Jul 2018 10:39:14 +0200 |
| Subject: i2c/mux, locking/core: Annotate the nested rt_mutex usage |
| |
| From: Peter Rosin <peda@axentia.se> |
| |
| [ Upstream commit 7b94ea50514d1a0dc94f02723b603c27bc0ea597 ] |
| |
| 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@google.com> |
| Tested-by: John Sperbeck <jsperbeck@google.com> |
| Signed-off-by: Peter Rosin <peda@axentia.se> |
| Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> |
| Cc: Davidlohr Bueso <dave@stgolabs.net> |
| Cc: Deepa Dinamani <deepadinamani@google.com> |
| Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| Cc: Peter Chang <dpf@google.com> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Philippe Ombredanne <pombredanne@nexb.com> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Cc: Will Deacon <will.deacon@arm.com> |
| Cc: Wolfram Sang <wsa@the-dreams.de> |
| Link: http://lkml.kernel.org/r/20180720083914.1950-3-peda@axentia.se |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/i2c/i2c-core-base.c | 2 +- |
| drivers/i2c/i2c-mux.c | 4 ++-- |
| 2 files changed, 3 insertions(+), 3 deletions(-) |
| |
| --- a/drivers/i2c/i2c-core-base.c |
| +++ b/drivers/i2c/i2c-core-base.c |
| @@ -638,7 +638,7 @@ static int i2c_check_addr_busy(struct i2 |
| 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)); |
| } |
| |
| /** |
| --- a/drivers/i2c/i2c-mux.c |
| +++ b/drivers/i2c/i2c-mux.c |
| @@ -144,7 +144,7 @@ static void i2c_mux_lock_bus(struct i2c_ |
| 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 i |
| 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); |
| } |
| |