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803766cbf8
The pasid_lock is used to synchronize different threads from modifying a same pasid directory entry at the same time. It causes below lockdep splat. [ 83.296538] ======================================================== [ 83.296538] WARNING: possible irq lock inversion dependency detected [ 83.296539] 5.12.0-rc3+ #25 Tainted: G W [ 83.296539] -------------------------------------------------------- [ 83.296540] bash/780 just changed the state of lock: [ 83.296540] ffffffff82b29c98 (device_domain_lock){..-.}-{2:2}, at: iommu_flush_dev_iotlb.part.0+0x32/0x110 [ 83.296547] but this lock took another, SOFTIRQ-unsafe lock in the past: [ 83.296547] (pasid_lock){+.+.}-{2:2} [ 83.296548] and interrupts could create inverse lock ordering between them. [ 83.296549] other info that might help us debug this: [ 83.296549] Chain exists of: device_domain_lock --> &iommu->lock --> pasid_lock [ 83.296551] Possible interrupt unsafe locking scenario: [ 83.296551] CPU0 CPU1 [ 83.296552] ---- ---- [ 83.296552] lock(pasid_lock); [ 83.296553] local_irq_disable(); [ 83.296553] lock(device_domain_lock); [ 83.296554] lock(&iommu->lock); [ 83.296554] <Interrupt> [ 83.296554] lock(device_domain_lock); [ 83.296555] *** DEADLOCK *** Fix it by replacing the pasid_lock with an atomic exchange operation. Reported-and-tested-by: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Link: https://lore.kernel.org/r/20210320020916.640115-1-baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel <jroedel@suse.de> |
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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.