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[2a02:3100:b14d:3b00:3c96:9472:d1b6:5cc4]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-38c5c1b5492sm19007927f8f.73.2025.02.05.05.49.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Feb 2025 05:49:27 -0800 (PST) Message-ID: <72397ae6-43aa-4a15-be5e-cdfe06b2c7ea@gmail.com> Date: Wed, 5 Feb 2025 14:49:46 +0100 Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: Herve Codina , Wolfram Sang Cc: "linux-i2c@vger.kernel.org" From: Heiner Kallweit Subject: [PATCH v2 RFC] i2c: Fix deadlock on adapter removal Autocrypt: addr=hkallweit1@gmail.com; keydata= xsFNBF/0ZFUBEAC0eZyktSE7ZNO1SFXL6cQ4i4g6Ah3mOUIXSB4pCY5kQ6OLKHh0FlOD5/5/ sY7IoIouzOjyFdFPnz4Bl3927ClT567hUJJ+SNaFEiJ9vadI6vZm2gcY4ExdIevYHWe1msJF MVE4yNwdS+UsPeCF/6CQQTzHc+n7DomE7fjJD5J1hOJjqz2XWe71fTvYXzxCFLwXXbBiqDC9 dNqOe5odPsa4TsWZ09T33g5n2nzTJs4Zw8fCy8rLqix/raVsqr8fw5qM66MVtdmEljFaJ9N8 /W56qGCp+H8Igk/F7CjlbWXiOlKHA25mPTmbVp7VlFsvsmMokr/imQr+0nXtmvYVaKEUwY2g 86IU6RAOuA8E0J5bD/BeyZdMyVEtX1kT404UJZekFytJZrDZetwxM/cAH+1fMx4z751WJmxQ J7mIXSPuDfeJhRDt9sGM6aRVfXbZt+wBogxyXepmnlv9K4A13z9DVLdKLrYUiu9/5QEl6fgI kPaXlAZmJsQfoKbmPqCHVRYj1lpQtDM/2/BO6gHASflWUHzwmBVZbS/XRs64uJO8CB3+V3fa cIivllReueGCMsHh6/8wgPAyopXOWOxbLsZ291fmZqIR0L5Y6b2HvdFN1Xhc+YrQ8TKK+Z4R mJRDh0wNQ8Gm89g92/YkHji4jIWlp2fwzCcx5+lZCQ1XdqAiHQARAQABzSZIZWluZXIgS2Fs bHdlaXQgPGhrYWxsd2VpdDFAZ21haWwuY29tPsLBjgQTAQgAOBYhBGxfqY/yOyXjyjJehXLe ig9U8DoMBQJf9GRVAhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEHLeig9U8DoMSycQ AJbfg8HZEK0ljV4M8nvdaiNixWAufrcZ+SD8zhbxl8GispK4F3Yo+20Y3UoZ7FcIidJWUUJL axAOkpI/70YNhlqAPMsuudlAieeYZKjIv1WV5ucNZ3VJ7dC+dlVqQdAr1iD869FZXvy91KhJ wYulyCf+s4T9YgmLC6jLMBZghKIf1uhSd0NzjyCqYWbk2ZxByZHgunEShOhHPHswu3Am0ftt ePaYIHgZs+Vzwfjs8I7EuW/5/f5G9w1vibXxtGY/GXwgGGHRDjFM7RSprGOv4F5eMGh+NFUJ TU9N96PQYMwXVxnQfRXl8O6ffSVmFx4H9rovxWPKobLmqQL0WKLLVvA/aOHCcMKgfyKRcLah 57vGC50Ga8oT2K1g0AhKGkyJo7lGXkMu5yEs0m9O+btqAB261/E3DRxfI1P/tvDZpLJKtq35 dXsj6sjvhgX7VxXhY1wE54uqLLHY3UZQlmH3QF5t80MS7/KhxB1pO1Cpcmkt9hgyzH8+5org +9wWxGUtJWNP7CppY+qvv3SZtKJMKsxqk5coBGwNkMms56z4qfJm2PUtJQGjA65XWdzQACib 2iaDQoBqGZfXRdPT0tC1H5kUJuOX4ll1hI/HBMEFCcO8++Bl2wcrUsAxLzGvhINVJX2DAQaF aNetToazkCnzubKfBOyiTqFJ0b63c5dqziAgzsFNBF/0ZFUBEADF8UEZmKDl1w/UxvjeyAeX kghYkY3bkK6gcIYXdLRfJw12GbvMioSguvVzASVHG8h7NbNjk1yur6AONfbUpXKSNZ0skV8V fG+ppbaY+zQofsSMoj5gP0amwbwvPzVqZCYJai81VobefTX2MZM2Mg/ThBVtGyzV3NeCpnBa 8AX3s9rrX2XUoCibYotbbxx9afZYUFyflOc7kEpc9uJXIdaxS2Z6MnYLHsyVjiU6tzKCiVOU KJevqvzPXJmy0xaOVf7mhFSNQyJTrZpLa+tvB1DQRS08CqYtIMxRrVtC0t0LFeQGly6bOngr ircurWJiJKbSXVstLHgWYiq3/GmCSx/82ObeLO3PftklpRj8d+kFbrvrqBgjWtMH4WtK5uN5 1WJ71hWJfNchKRlaJ3GWy8KolCAoGsQMovn/ZEXxrGs1ndafu47yXOpuDAozoHTBGvuSXSZo ythk/0EAuz5IkwkhYBT1MGIAvNSn9ivE5aRnBazugy0rTRkVggHvt3/7flFHlGVGpBHxFUwb /a4UjJBPtIwa4tWR8B1Ma36S8Jk456k2n1id7M0LQ+eqstmp6Y+UB+pt9NX6t0Slw1NCdYTW gJezWTVKF7pmTdXszXGxlc9kTrVUz04PqPjnYbv5UWuDd2eyzGjrrFOsJEi8OK2d2j4FfF++ AzOMdW09JVqejQARAQABwsF2BBgBCAAgFiEEbF+pj/I7JePKMl6Fct6KD1TwOgwFAl/0ZFUC GwwACgkQct6KD1TwOgxUfg//eAoYc0Vm4NrxymfcY30UjHVD0LgSvU8kUmXxil3qhFPS7KA+ y7tgcKLHOkZkXMX5MLFcS9+SmrAjSBBV8omKoHNo+kfFx/dUAtz0lot8wNGmWb+NcHeKM1eb nwUMOEa1uDdfZeKef/U/2uHBceY7Gc6zPZPWgXghEyQMTH2UhLgeam8yglyO+A6RXCh+s6ak Wje7Vo1wGK4eYxp6pwMPJXLMsI0ii/2k3YPEJPv+yJf90MbYyQSbkTwZhrsokjQEaIfjrIk3 rQRjTve/J62WIO28IbY/mENuGgWehRlTAbhC4BLTZ5uYS0YMQCR7v9UGMWdNWXFyrOB6PjSu Trn9MsPoUc8qI72mVpxEXQDLlrd2ijEWm7Nrf52YMD7hL6rXXuis7R6zY8WnnBhW0uCfhajx q+KuARXC0sDLztcjaS3ayXonpoCPZep2Bd5xqE4Ln8/COCslP7E92W1uf1EcdXXIrx1acg21 H/0Z53okMykVs3a8tECPHIxnre2UxKdTbCEkjkR4V6JyplTS47oWMw3zyI7zkaadfzVFBxk2 lo/Tny+FX1Azea3Ce7oOnRUEZtWSsUidtIjmL8YUQFZYm+JUIgfRmSpMFq8JP4VH43GXpB/S OCrl+/xujzvoUBFV/cHKjEQYBxo+MaiQa1U54ykM2W4DnHb1UiEf5xDkFd4= i2c_del_adapter() can be called recursively if it has an i2c mux on the bus. This results in a deadlock. We use the lock to protect from parallel unregistering of clients in case driver and adapter are removed at the same time. The fix approach is based on the fact that the used iterators are klist-based. So it's safe to remove list elements during the iteration, and we don't have to acquire the core lock. As a result we just have to prevent that i2c_unregister_device() is executed in parallel for the same client. Use an atomic bit op for this purpose. Fixes: 56a50667cbcf ("i2c: Replace list-based mechanism for handling auto-detected clients") Reported-by: Herve Codina Signed-off-by: Heiner Kallweit Tested-by: Herve Codina --- v2: - define I2C_CLIENT_UNREGISTERING as a bit number --- drivers/i2c/i2c-core-base.c | 9 +++------ include/linux/i2c.h | 4 +++- 2 files changed, 6 insertions(+), 7 deletions(-) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index 6eade239f..44b861eb4 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -1059,6 +1059,9 @@ void i2c_unregister_device(struct i2c_client *client) if (IS_ERR_OR_NULL(client)) return; + if (test_and_set_bit(I2C_CLIENT_UNREGISTERING, &client->flags)) + return; + if (client->dev.of_node) { of_node_clear_flag(client->dev.of_node, OF_POPULATED); of_node_put(client->dev.of_node); @@ -1354,7 +1357,6 @@ delete_device_store(struct device *dev, struct device_attribute *attr, return -EINVAL; } - mutex_lock(&core_lock); /* Make sure the device was added through sysfs */ child_dev = device_find_child(&adap->dev, &addr, __i2c_find_user_addr); if (child_dev) { @@ -1364,7 +1366,6 @@ delete_device_store(struct device *dev, struct device_attribute *attr, dev_err(dev, "Can't find userspace-created device at %#x\n", addr); count = -ENOENT; } - mutex_unlock(&core_lock); return count; } @@ -1745,10 +1746,8 @@ void i2c_del_adapter(struct i2c_adapter *adap) * we can't remove the dummy devices during the first pass: they * could have been instantiated by real devices wishing to clean * them up properly, so we give them a chance to do that first. */ - mutex_lock(&core_lock); device_for_each_child(&adap->dev, NULL, __unregister_client); device_for_each_child(&adap->dev, NULL, __unregister_dummy); - mutex_unlock(&core_lock); /* device name is gone after device_unregister */ dev_dbg(&adap->dev, "adapter [%s] unregistered\n", adap->name); @@ -2002,12 +2001,10 @@ static int __i2c_unregister_detected_client(struct device *dev, void *argp) */ void i2c_del_driver(struct i2c_driver *driver) { - mutex_lock(&core_lock); /* Satisfy __must_check, function can't fail */ if (driver_for_each_device(&driver->driver, NULL, NULL, __i2c_unregister_detected_client)) { } - mutex_unlock(&core_lock); driver_unregister(&driver->driver); pr_debug("driver [%s] unregistered\n", driver->driver.name); diff --git a/include/linux/i2c.h b/include/linux/i2c.h index c31fd1dba..f5de17590 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -325,7 +325,7 @@ struct i2c_driver { * managing the device. */ struct i2c_client { - unsigned short flags; /* div., see below */ + unsigned long flags; /* div., see below */ #define I2C_CLIENT_PEC 0x04 /* Use Packet Error Checking */ #define I2C_CLIENT_TEN 0x10 /* we have a ten bit chip address */ /* Must equal I2C_M_TEN below */ @@ -336,6 +336,8 @@ struct i2c_client { #define I2C_CLIENT_USER 0x200 /* client was userspace-created */ #define I2C_CLIENT_SCCB 0x9000 /* Use Omnivision SCCB protocol */ /* Must match I2C_M_STOP|IGNORE_NAK */ +/* following flags are bit numbers */ +#define I2C_CLIENT_UNREGISTERING 31 /* client is being unregistered */ unsigned short addr; /* chip address - NOTE: 7bit */ /* addresses are stored in the */