linux/kernel/kthread.c, branch v6.4

Merge tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2023-04-28T02:42:02Z

Pull MM updates from Andrew Morton: - Nick Piggin's "shoot lazy tlbs" series, to improve the peformance of switching from a user process to a kernel thread. - More folio conversions from Kefeng Wang, Zhang Peng and Pankaj Raghav. - zsmalloc performance improvements from Sergey Senozhatsky. - Yue Zhao has found and fixed some data race issues around the alteration of memcg userspace tunables. - VFS rationalizations from Christoph Hellwig: - removal of most of the callers of write_one_page() - make __filemap_get_folio()'s return value more useful - Luis Chamberlain has changed tmpfs so it no longer requires swap backing. Use `mount -o noswap'. - Qi Zheng has made the slab shrinkers operate locklessly, providing some scalability benefits. - Keith Busch has improved dmapool's performance, making part of its operations O(1) rather than O(n). - Peter Xu adds the UFFD_FEATURE_WP_UNPOPULATED feature to userfaultd, permitting userspace to wr-protect anon memory unpopulated ptes. - Kirill Shutemov has changed MAX_ORDER's meaning to be inclusive rather than exclusive, and has fixed a bunch of errors which were caused by its unintuitive meaning. - Axel Rasmussen give userfaultfd the UFFDIO_CONTINUE_MODE_WP feature, which causes minor faults to install a write-protected pte. - Vlastimil Babka has done some maintenance work on vma_merge(): cleanups to the kernel code and improvements to our userspace test harness. - Cleanups to do_fault_around() by Lorenzo Stoakes. - Mike Rapoport has moved a lot of initialization code out of various mm/ files and into mm/mm_init.c. - Lorenzo Stoakes removd vmf_insert_mixed_prot(), which was added for DRM, but DRM doesn't use it any more. - Lorenzo has also coverted read_kcore() and vread() to use iterators and has thereby removed the use of bounce buffers in some cases. - Lorenzo has also contributed further cleanups of vma_merge(). - Chaitanya Prakash provides some fixes to the mmap selftesting code. - Matthew Wilcox changes xfs and afs so they no longer take sleeping locks in ->map_page(), a step towards RCUification of pagefaults. - Suren Baghdasaryan has improved mmap_lock scalability by switching to per-VMA locking. - Frederic Weisbecker has reworked the percpu cache draining so that it no longer causes latency glitches on cpu isolated workloads. - Mike Rapoport cleans up and corrects the ARCH_FORCE_MAX_ORDER Kconfig logic. - Liu Shixin has changed zswap's initialization so we no longer waste a chunk of memory if zswap is not being used. - Yosry Ahmed has improved the performance of memcg statistics flushing. - David Stevens has fixed several issues involving khugepaged, userfaultfd and shmem. - Christoph Hellwig has provided some cleanup work to zram's IO-related code paths. - David Hildenbrand has fixed up some issues in the selftest code's testing of our pte state changing. - Pankaj Raghav has made page_endio() unneeded and has removed it. - Peter Xu contributed some rationalizations of the userfaultfd selftests. - Yosry Ahmed has fixed an issue around memcg's page recalim accounting. - Chaitanya Prakash has fixed some arm-related issues in the selftests/mm code. - Longlong Xia has improved the way in which KSM handles hwpoisoned pages. - Peter Xu fixes a few issues with uffd-wp at fork() time. - Stefan Roesch has changed KSM so that it may now be used on a per-process and per-cgroup basis. * tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (369 commits) mm,unmap: avoid flushing TLB in batch if PTE is inaccessible shmem: restrict noswap option to initial user namespace mm/khugepaged: fix conflicting mods to collapse_file() sparse: remove unnecessary 0 values from rc mm: move 'mmap_min_addr' logic from callers into vm_unmapped_area() hugetlb: pte_alloc_huge() to replace huge pte_alloc_map() maple_tree: fix allocation in mas_sparse_area() mm: do not increment pgfault stats when page fault handler retries zsmalloc: allow only one active pool compaction context selftests/mm: add new selftests for KSM mm: add new KSM process and sysfs knobs mm: add new api to enable ksm per process mm: shrinkers: fix debugfs file permissions mm: don't check VMA write permissions if the PTE/PMD indicates write permissions migrate_pages_batch: fix statistics for longterm pin retry userfaultfd: use helper function range_in_vma() lib/show_mem.c: use for_each_populated_zone() simplify code mm: correct arg in reclaim_pages()/reclaim_clean_pages_from_list() fs/buffer: convert create_page_buffers to folio_create_buffers fs/buffer: add folio_create_empty_buffers helper ...

lazy tlb: introduce lazy tlb mm refcount helper functions

2023-03-28T23:20:08Z

Add explicit _lazy_tlb annotated functions for lazy tlb mm refcounting. This makes the lazy tlb mm references more obvious, and allows the refcounting scheme to be modified in later changes. There is no functional change with this patch. Link: https://lkml.kernel.org/r/20230203071837.1136453-3-npiggin@gmail.com Signed-off-by: Nicholas Piggin Acked-by: Linus Torvalds Cc: Andy Lutomirski Cc: Catalin Marinas Cc: Christophe Leroy Cc: Dave Hansen Cc: Michael Ellerman Cc: Nadav Amit Cc: Peter Zijlstra Cc: Rik van Riel Cc: Will Deacon Signed-off-by: Andrew Morton

kthread: simplify kthread_use_mm refcounting

2023-03-28T23:20:07Z

Patch series "shoot lazy tlbs (lazy tlb refcount scalability improvement)", v7. This series improves scalability of context switching between user and kernel threads on large systems with a threaded process spread across a lot of CPUs. Discussion of v6 here: https://lore.kernel.org/linux-mm/20230118080011.2258375-1-npiggin@gmail.com/ This patch (of 5): Remove the special case avoiding refcounting when the mm to be used is the same as the kernel thread's active (lazy tlb) mm. kthread_use_mm() should not be such a performance critical path that this matters much. This simplifies a later change to lazy tlb mm refcounting. Link: https://lkml.kernel.org/r/20230203071837.1136453-1-npiggin@gmail.com Link: https://lkml.kernel.org/r/20230203071837.1136453-2-npiggin@gmail.com Signed-off-by: Nicholas Piggin Acked-by: Linus Torvalds Cc: Andy Lutomirski Cc: Catalin Marinas Cc: Dave Hansen Cc: Linus Torvalds Cc: Nadav Amit Cc: Peter Zijlstra Cc: Rik van Riel Cc: Will Deacon Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Signed-off-by: Andrew Morton

kthread: Pass in the thread's name during creation

2023-03-12T09:54:36Z

This has us pass in the thread's name during creation in kernel_thread. Signed-off-by: Mike Christie Acked-by: Michael S. Tsirkin Signed-off-by: Christian Brauner (Microsoft)

kernel: Allow a kernel thread's name to be set in copy_process

2023-03-12T09:52:46Z

This patch allows kernel users to pass in the thread name so it can be set during creation instead of having to use set_task_comm after the thread is created. Signed-off-by: Mike Christie Acked-by: Michael S. Tsirkin Signed-off-by: Christian Brauner (Microsoft)

kthread_worker: check all delayed works when destroy kthread worker

2023-02-03T06:50:02Z

When destroying a kthread worker warn if there are still some pending delayed works. This indicates that the caller should clear all pending delayed works before destroying the kthread worker. Link: https://lkml.kernel.org/r/20230104144230.938521-1-qiang1.zhang@intel.com Signed-off-by: Zqiang Acked-by: Tejun Heo Reviewed-by: Petr Mladek Signed-off-by: Andrew Morton

Merge tag 'interrupting_kthread_stop-for-v5.20' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-10-09T23:01:59Z

Pull kthread update from Eric Biederman: "Break out of wait loops on kthread_stop() This is a small tweak to kthread_stop so it breaks out of interruptible waits, that don't explicitly test for kthread_stop. These interruptible waits occassionaly occur in kernel threads do to code sharing" * tag 'interrupting_kthread_stop-for-v5.20' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: signal: break out of wait loops on kthread_stop()

treewide: Drop WARN_ON_FUNCTION_MISMATCH

2022-09-26T17:13:14Z

CONFIG_CFI_CLANG no longer breaks cross-module function address equality, which makes WARN_ON_FUNCTION_MISMATCH unnecessary. Remove the definition and switch back to WARN_ON_ONCE. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Tested-by: Kees Cook Tested-by: Nathan Chancellor Acked-by: Peter Zijlstra (Intel) Tested-by: Peter Zijlstra (Intel) Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220908215504.3686827-15-samitolvanen@google.com

signal: break out of wait loops on kthread_stop()

2022-07-18T14:53:38Z

I was recently surprised to learn that msleep_interruptible(), wait_for_completion_interruptible_timeout(), and related functions simply hung when I called kthread_stop() on kthreads using them. The solution to fixing the case with msleep_interruptible() was more simply to move to schedule_timeout_interruptible(). Why? The reason is that msleep_interruptible(), and many functions just like it, has a loop like this: while (timeout && !signal_pending(current)) timeout = schedule_timeout_interruptible(timeout); The call to kthread_stop() woke up the thread, so schedule_timeout_ interruptible() returned early, but because signal_pending() returned true, it went back into another timeout, which was never woken up. This wait loop pattern is common to various pieces of code, and I suspect that the subtle misuse in a kthread that caused a deadlock in the code I looked at last week is also found elsewhere. So this commit causes signal_pending() to return true when kthread_stop() is called, by setting TIF_NOTIFY_SIGNAL. The same also probably applies to the similar kthread_park() functionality, but that can be addressed later, as its semantics are slightly different. Cc: Eric W. Biederman Signed-off-by: Jason A. Donenfeld v1: https://lkml.kernel.org/r/20220627120020.608117-1-Jason@zx2c4.com v2: https://lkml.kernel.org/r/20220627145716.641185-1-Jason@zx2c4.com v3: https://lkml.kernel.org/r/20220628161441.892925-1-Jason@zx2c4.com v4: https://lkml.kernel.org/r/20220711202136.64458-1-Jason@zx2c4.com v5: https://lkml.kernel.org/r/20220711232123.136330-1-Jason@zx2c4.com Signed-off-by: Eric W. Biederman

kthread: make it clear that kthread_create_on_node() might be terminated by any fatal signal

2022-06-17T02:11:30Z

The comments in kernel/kthread.c create a feeling that only SIGKILL is able to terminate the creation of kernel kthreads by kthread_create()/_on_node()/_on_cpu() APIs. In reality, wait_for_completion_killable() might be killed by any fatal signal that does not have a custom handler: (!siginmask(signr, SIG_KERNEL_IGNORE_MASK|SIG_KERNEL_STOP_MASK) && \ (t)->sighand->action[(signr)-1].sa.sa_handler == SIG_DFL) static inline void signal_wake_up(struct task_struct *t, bool resume) { signal_wake_up_state(t, resume ? TASK_WAKEKILL : 0); } static void complete_signal(int sig, struct task_struct *p, enum pid_type type) { [...] /* * Found a killable thread. If the signal will be fatal, * then start taking the whole group down immediately. */ if (sig_fatal(p, sig) ...) { if (!sig_kernel_coredump(sig)) { [...] do { task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK); sigaddset(&t->pending.signal, SIGKILL); signal_wake_up(t, 1); } while_each_thread(p, t); return; } } } Update the comments in kernel/kthread.c to make this more obvious. The motivation for this change was debugging why a module initialization failed. The module was being loaded from initrd. It "magically" failed when systemd was switching to the real root. The clean up operations sent SIGTERM to various pending processed that were started from initrd. Link: https://lkml.kernel.org/r/20220315102444.2380-1-pmladek@suse.com Signed-off-by: Petr Mladek Reviewed-by: "Eric W. Biederman" Cc: Peter Zijlstra Cc: Mathieu Desnoyers Cc: Kees Cook Cc: Marco Elver Cc: Jens Axboe Cc: Thomas Gleixner Signed-off-by: Andrew Morton