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From: tip-bot for Peter Rosin <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: will.deacon@arm.com, torvalds@linux-foundation.org,
	hpa@zytor.com, tglx@linutronix.de, jsperbeck@google.com,
	wsa@the-dreams.de, linux-kernel@vger.kernel.org,
	mingo@kernel.org, dave@stgolabs.net, dpf@google.com,
	pombredanne@nexb.com, peda@axentia.se, peterz@infradead.org,
	gregkh@linuxfoundation.org, deepadinamani@google.com
Subject: [tip:locking/urgent] i2c/mux, locking/core: Annotate the nested rt_mutex usage
Date: Wed, 25 Jul 2018 07:19:34 -0700	[thread overview]
Message-ID: <tip-7b94ea50514d1a0dc94f02723b603c27bc0ea597@git.kernel.org> (raw)
In-Reply-To: <20180720083914.1950-3-peda@axentia.se>

Commit-ID:  7b94ea50514d1a0dc94f02723b603c27bc0ea597
Gitweb:     https://git.kernel.org/tip/7b94ea50514d1a0dc94f02723b603c27bc0ea597
Author:     Peter Rosin <peda@axentia.se>
AuthorDate: Fri, 20 Jul 2018 10:39:14 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
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@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>
---
 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);
 }
 

  reply	other threads:[~2018-07-25 14:20 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-20  8:39 [PATCH v4 0/2] Fix lockdep warning with nested instances of i2c-mux Peter Rosin
2018-07-20  8:39 ` [PATCH v4 1/2] rtmutex: allow specifying a subclass for nested locking Peter Rosin
2018-07-25 14:18   ` [tip:locking/urgent] locking/rtmutex: Allow " tip-bot for Peter Rosin
2018-09-10 23:27   ` [PATCH v4 1/2] rtmutex: allow " Steven Rostedt
2018-09-11  0:58     ` Peter Rosin
2018-07-20  8:39 ` [PATCH v4 2/2] i2c: mux: annotate the nested rt_mutex usage Peter Rosin
2018-07-25 14:19   ` tip-bot for Peter Rosin [this message]
2018-07-30 16:09     ` [tip:locking/urgent] i2c/mux, locking/core: Annotate " Peter Rosin
2018-07-30 17:17       ` Ingo Molnar

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