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Vaibhav Jain
a5d6a3e73a
While removing large number of mappings from hash page tables for large memory systems as soft-lockup is reported because of the time spent inside htap_remove_mapping() like one below: watchdog: BUG: soft lockup - CPU#8 stuck for 23s! <snip> NIP plpar_hcall+0x38/0x58 LR pSeries_lpar_hpte_invalidate+0x68/0xb0 Call Trace: 0x1fffffffffff000 (unreliable) pSeries_lpar_hpte_removebolted+0x9c/0x230 hash__remove_section_mapping+0xec/0x1c0 remove_section_mapping+0x28/0x3c arch_remove_memory+0xfc/0x150 devm_memremap_pages_release+0x180/0x2f0 devm_action_release+0x30/0x50 release_nodes+0x28c/0x300 device_release_driver_internal+0x16c/0x280 unbind_store+0x124/0x170 drv_attr_store+0x44/0x60 sysfs_kf_write+0x64/0x90 kernfs_fop_write+0x1b0/0x290 __vfs_write+0x3c/0x70 vfs_write+0xd4/0x270 ksys_write+0xdc/0x130 system_call+0x5c/0x70 Fix this by adding a cond_resched() to the loop in htap_remove_mapping() that issues hcall to remove hpte mapping. The call to cond_resched() is issued every HZ jiffies which should prevent the soft-lockup from being reported. Suggested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210404163148.321346-1-vaibhav@linux.ibm.com
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.