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The global rwsem dmar_global_lock was introduced by commit3a5670e8ac("iommu/vt-d: Introduce a rwsem to protect global data structures"). It is used to protect DMAR related global data from DMAR hotplug operations. The dmar_global_lock used in the intel_iommu_init() might cause recursive locking issue, for example, intel_iommu_get_resv_regions() is taking the dmar_global_lock from within a section where intel_iommu_init() already holds it via probe_acpi_namespace_devices(). Using dmar_global_lock in intel_iommu_init() could be relaxed since it is unlikely that any IO board must be hot added before the IOMMU subsystem is initialized. This eliminates the possible recursive locking issue by moving down DMAR hotplug support after the IOMMU is initialized and removing the uses of dmar_global_lock in intel_iommu_init(). Fixes:d5692d4af0("iommu/vt-d: Fix suspicious RCU usage in probe_acpi_namespace_devices()") Reported-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Link: https://lore.kernel.org/r/894db0ccae854b35c73814485569b634237b5538.1657034828.git.robin.murphy@arm.com Link: https://lore.kernel.org/r/20220718235325.3952426-1-baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.