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Commitde0aa7b2f9("PCI: hv: Fix 2 hang issues in hv_compose_msi_msg()") uses local_bh_disable()/enable(), because hv_pci_onchannelcallback() can also run in tasklet context as the channel event callback, so bottom halves should be disabled to prevent a race condition. With CONFIG_PROVE_LOCKING=y in the recent mainline, or old kernels that don't have commitf71b74bca6("irq/softirqs: Use lockdep to assert IRQs are disabled/enabled"), when the upper layer IRQ code calls hv_compose_msi_msg() with local IRQs disabled, we'll see a warning at the beginning of __local_bh_enable_ip(): IRQs not enabled as expected WARNING: CPU: 0 PID: 408 at kernel/softirq.c:162 __local_bh_enable_ip The warning exposes an issue inde0aa7b2f9: local_bh_enable() can potentially call do_softirq(), which is not supposed to run when local IRQs are disabled. Let's fix this by using local_irq_save()/restore() instead. Note: hv_pci_onchannelcallback() is not a hot path because it's only called when the PCI device is hot added and removed, which is infrequent. Fixes:de0aa7b2f9("PCI: hv: Fix 2 hang issues in hv_compose_msi_msg()") Signed-off-by: Dexuan Cui <decui@microsoft.com> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com> Cc: stable@vger.kernel.org Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: K. Y. Srinivasan <kys@microsoft.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.