user/sven/linux.git/kernel/locking, branch v5.16.13

lockdep: Correct lock_classes index mapping

2022-02-23T11:06:05Z

commit 28df029d53a2fd80c1b8674d47895648ad26dcfb upstream. A kernel exception was hit when trying to dump /proc/lockdep_chains after lockdep report "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!": Unable to handle kernel paging request at virtual address 00054005450e05c3 ... 00054005450e05c3] address between user and kernel address ranges ... pc : [0xffffffece769b3a8] string+0x50/0x10c lr : [0xffffffece769ac88] vsnprintf+0x468/0x69c ... Call trace: string+0x50/0x10c vsnprintf+0x468/0x69c seq_printf+0x8c/0xd8 print_name+0x64/0xf4 lc_show+0xb8/0x128 seq_read_iter+0x3cc/0x5fc proc_reg_read_iter+0xdc/0x1d4 The cause of the problem is the function lock_chain_get_class() will shift lock_classes index by 1, but the index don't need to be shifted anymore since commit 01bb6f0af992 ("locking/lockdep: Change the range of class_idx in held_lock struct") already change the index to start from 0. The lock_classes[-1] located at chain_hlocks array. When printing lock_classes[-1] after the chain_hlocks entries are modified, the exception happened. The output of lockdep_chains are incorrect due to this problem too. Fixes: f611e8cf98ec ("lockdep: Take read/write status in consideration when generate chainkey") Signed-off-by: Cheng Jui Wang Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Boqun Feng Link: https://lore.kernel.org/r/20220210105011.21712-1-cheng-jui.wang@mediatek.com Signed-off-by: Greg Kroah-Hartman

kernel/locking: Use a pointer in ww_mutex_trylock().

2022-01-27T11:01:31Z

[ Upstream commit 2202e15b2b1a946ce760d96748cd7477589701ab ] mutex_acquire_nest() expects a pointer, pass the pointer. Fixes: 12235da8c80a1 ("kernel/locking: Add context to ww_mutex_trylock()") Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20211104122706.frk52zxbjorso2kv@linutronix.de Signed-off-by: Sasha Levin

locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner()

2021-12-18T09:55:51Z

Optimistic spinning needs to be terminated when the spinning waiter is not longer the top waiter on the lock, but the condition is negated. It terminates if the waiter is the top waiter, which is defeating the whole purpose. Fixes: c3123c431447 ("locking/rtmutex: Dont dereference waiter lockless") Signed-off-by: Zqiang Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211217074207.77425-1-qiang1.zhang@intel.com

locking/rwsem: Optimize down_read_trylock() under highly contended case

2021-11-23T08:45:36Z

We found that a process with 10 thousnads threads has been encountered a regression problem from Linux-v4.14 to Linux-v5.4. It is a kind of workload which will concurrently allocate lots of memory in different threads sometimes. In this case, we will see the down_read_trylock() with a high hotspot. Therefore, we suppose that rwsem has a regression at least since Linux-v5.4. In order to easily debug this problem, we write a simply benchmark to create the similar situation lile the following. ```c++ #include #include #include #include #include #include #include #include #include volatile int mutex; void trigger(int cpu, char* ptr, std::size_t sz) { cpu_set_t set; CPU_ZERO(&set); CPU_SET(cpu, &set); assert(pthread_setaffinity_np(pthread_self(), sizeof(set), &set) == 0); while (mutex); for (std::size_t i = 0; i < sz; i += 4096) { *ptr = '\0'; ptr += 4096; } } int main(int argc, char* argv[]) { std::size_t sz = 100; if (argc > 1) sz = atoi(argv[1]); auto nproc = std::thread::hardware_concurrency(); std::vector thr; sz <<= 30; auto* ptr = mmap(nullptr, sz, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0); assert(ptr != MAP_FAILED); char* cptr = static_cast(ptr); auto run = sz / nproc; run = (run >> 12) << 12; mutex = 1; for (auto i = 0U; i < nproc; ++i) { thr.emplace_back(std::thread([i, cptr, run]() { trigger(i, cptr, run); })); cptr += run; } rusage usage_start; getrusage(RUSAGE_SELF, &usage_start); auto start = std::chrono::system_clock::now(); mutex = 0; for (auto& t : thr) t.join(); rusage usage_end; getrusage(RUSAGE_SELF, &usage_end); auto end = std::chrono::system_clock::now(); timeval utime; timeval stime; timersub(&usage_end.ru_utime, &usage_start.ru_utime, &utime); timersub(&usage_end.ru_stime, &usage_start.ru_stime, &stime); printf("usr: %ld.%06ld\n", utime.tv_sec, utime.tv_usec); printf("sys: %ld.%06ld\n", stime.tv_sec, stime.tv_usec); printf("real: %lu\n", std::chrono::duration_cast(end - start).count()); return 0; } ``` The functionality of above program is simply which creates `nproc` threads and each of them are trying to touch memory (trigger page fault) on different CPU. Then we will see the similar profile by `perf top`. 25.55% [kernel] [k] down_read_trylock 14.78% [kernel] [k] handle_mm_fault 13.45% [kernel] [k] up_read 8.61% [kernel] [k] clear_page_erms 3.89% [kernel] [k] __do_page_fault The highest hot instruction, which accounts for about 92%, in down_read_trylock() is cmpxchg like the following. 91.89 │ lock cmpxchg %rdx,(%rdi) Sice the problem is found by migrating from Linux-v4.14 to Linux-v5.4, so we easily found that the commit ddb20d1d3aed ("locking/rwsem: Optimize down_read_trylock()") caused the regression. The reason is that the commit assumes the rwsem is not contended at all. But it is not always true for mmap lock which could be contended with thousands threads. So most threads almost need to run at least 2 times of "cmpxchg" to acquire the lock. The overhead of atomic operation is higher than non-atomic instructions, which caused the regression. By using the above benchmark, the real executing time on a x86-64 system before and after the patch were: Before Patch After Patch # of Threads real real reduced by ------------ ------ ------ ---------- 1 65,373 65,206 ~0.0% 4 15,467 15,378 ~0.5% 40 6,214 5,528 ~11.0% For the uncontended case, the new down_read_trylock() is the same as before. For the contended cases, the new down_read_trylock() is faster than before. The more contended, the more fast. Signed-off-by: Muchun Song Signed-off-by: Peter Zijlstra (Intel) Acked-by: Waiman Long Link: https://lore.kernel.org/r/20211118094455.9068-1-songmuchun@bytedance.com

locking/rwsem: Make handoff bit handling more consistent

2021-11-23T08:45:35Z

There are some inconsistency in the way that the handoff bit is being handled in readers and writers that lead to a race condition. Firstly, when a queue head writer set the handoff bit, it will clear it when the writer is being killed or interrupted on its way out without acquiring the lock. That is not the case for a queue head reader. The handoff bit will simply be inherited by the next waiter. Secondly, in the out_nolock path of rwsem_down_read_slowpath(), both the waiter and handoff bits are cleared if the wait queue becomes empty. For rwsem_down_write_slowpath(), however, the handoff bit is not checked and cleared if the wait queue is empty. This can potentially make the handoff bit set with empty wait queue. Worse, the situation in rwsem_down_write_slowpath() relies on wstate, a variable set outside of the critical section containing the ->count manipulation, this leads to race condition where RWSEM_FLAG_HANDOFF can be double subtracted, corrupting ->count. To make the handoff bit handling more consistent and robust, extract out handoff bit clearing code into the new rwsem_del_waiter() helper function. Also, completely eradicate wstate; always evaluate everything inside the same critical section. The common function will only use atomic_long_andnot() to clear bits when the wait queue is empty to avoid possible race condition. If the first waiter with handoff bit set is killed or interrupted to exit the slowpath without acquiring the lock, the next waiter will inherit the handoff bit. While at it, simplify the trylock for loop in rwsem_down_write_slowpath() to make it easier to read. Fixes: 4f23dbc1e657 ("locking/rwsem: Implement lock handoff to prevent lock starvation") Reported-by: Zhenhua Ma Suggested-by: Peter Zijlstra Signed-off-by: Waiman Long Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20211116012912.723980-1-longman@redhat.com

Merge branch 'akpm' (patches from Andrew)

2021-11-09T18:11:53Z

Merge more updates from Andrew Morton: "87 patches. Subsystems affected by this patch series: mm (pagecache and hugetlb), procfs, misc, MAINTAINERS, lib, checkpatch, binfmt, kallsyms, ramfs, init, codafs, nilfs2, hfs, crash_dump, signals, seq_file, fork, sysvfs, kcov, gdb, resource, selftests, and ipc" * emailed patches from Andrew Morton : (87 commits) ipc/ipc_sysctl.c: remove fallback for !CONFIG_PROC_SYSCTL ipc: check checkpoint_restore_ns_capable() to modify C/R proc files selftests/kselftest/runner/run_one(): allow running non-executable files virtio-mem: disallow mapping virtio-mem memory via /dev/mem kernel/resource: disallow access to exclusive system RAM regions kernel/resource: clean up and optimize iomem_is_exclusive() scripts/gdb: handle split debug for vmlinux kcov: replace local_irq_save() with a local_lock_t kcov: avoid enable+disable interrupts if !in_task() kcov: allocate per-CPU memory on the relevant node Documentation/kcov: define `ip' in the example Documentation/kcov: include types.h in the example sysv: use BUILD_BUG_ON instead of runtime check kernel/fork.c: unshare(): use swap() to make code cleaner seq_file: fix passing wrong private data seq_file: move seq_escape() to a header signal: remove duplicate include in signal.h crash_dump: remove duplicate include in crash_dump.h crash_dump: fix boolreturn.cocci warning hfs/hfsplus: use WARN_ON for sanity check ...

kallsyms: remove arch specific text and data check

2021-11-09T18:02:50Z

Patch series "sections: Unify kernel sections range check and use", v4. There are three head files(kallsyms.h, kernel.h and sections.h) which include the kernel sections range check, let's make some cleanup and unify them. 1. cleanup arch specific text/data check and fix address boundary check in kallsyms.h 2. make all the basic/core kernel range check function into sections.h 3. update all the callers, and use the helper in sections.h to simplify the code After this series, we have 5 APIs about kernel sections range check in sections.h * is_kernel_rodata() --- already in sections.h * is_kernel_core_data() --- come from core_kernel_data() in kernel.h * is_kernel_inittext() --- come from kernel.h and kallsyms.h * __is_kernel_text() --- add new internal helper * __is_kernel() --- add new internal helper Note: For the last two helpers, people should not use directly, consider to use corresponding function in kallsyms.h. This patch (of 11): Remove arch specific text and data check after commit 4ba66a976072 ("arch: remove blackfin port"), no need arch-specific text/data check. Link: https://lkml.kernel.org/r/20210930071143.63410-1-wangkefeng.wang@huawei.com Link: https://lkml.kernel.org/r/20210930071143.63410-2-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang Reviewed-by: Sergey Senozhatsky Cc: Arnd Bergmann Cc: Steven Rostedt Cc: Ingo Molnar Cc: David S. Miller Cc: Alexei Starovoitov Cc: Andrey Ryabinin Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Christophe Leroy Cc: Kefeng Wang Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Borislav Petkov Cc: Dmitry Vyukov Cc: Ivan Kokshaysky Cc: Matt Turner Cc: Michal Simek Cc: Petr Mladek Cc: Richard Henderson Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'akpm' (patches from Andrew)

2021-11-06T21:08:17Z

Merge misc updates from Andrew Morton: "257 patches. Subsystems affected by this patch series: scripts, ocfs2, vfs, and mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache, gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc, pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools, memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm, vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram, cleanups, kfence, and damon)" * emailed patches from Andrew Morton : (257 commits) mm/damon: remove return value from before_terminate callback mm/damon: fix a few spelling mistakes in comments and a pr_debug message mm/damon: simplify stop mechanism Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions Docs/admin-guide/mm/damon/start: simplify the content Docs/admin-guide/mm/damon/start: fix a wrong link Docs/admin-guide/mm/damon/start: fix wrong example commands mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on mm/damon: remove unnecessary variable initialization Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM) selftests/damon: support watermarks mm/damon/dbgfs: support watermarks mm/damon/schemes: activate schemes based on a watermarks mechanism tools/selftests/damon: update for regions prioritization of schemes mm/damon/dbgfs: support prioritization weights mm/damon/vaddr,paddr: support pageout prioritization mm/damon/schemes: prioritize regions within the quotas mm/damon/selftests: support schemes quotas mm/damon/dbgfs: support quotas of schemes ...

mm: make generic arch_is_kernel_initmem_freed() do what it says

2021-11-06T20:30:38Z

Commit 7a5da02de8d6 ("locking/lockdep: check for freed initmem in static_obj()") added arch_is_kernel_initmem_freed() which is supposed to report whether an object is part of already freed init memory. For the time being, the generic version of arch_is_kernel_initmem_freed() always reports 'false', allthough free_initmem() is generically called on all architectures. Therefore, change the generic version of arch_is_kernel_initmem_freed() to check whether free_initmem() has been called. If so, then check if a given address falls into init memory. To ease the use of system_state, move it out of line into its only caller which is lockdep.c Link: https://lkml.kernel.org/r/1d40783e676e07858be97d881f449ee7ea8adfb1.1633001016.git.christophe.leroy@csgroup.eu Signed-off-by: Christophe Leroy Cc: Gerald Schaefer Cc: Kefeng Wang Cc: Benjamin Herrenschmidt Cc: Heiko Carstens Cc: Paul Mackerras Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'rcu.2021.11.01a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

2021-11-02T03:25:38Z

Pull RCU updates from Paul McKenney: - Miscellaneous fixes - Torture-test updates for smp_call_function(), most notably improved checking of module parameters. - Tasks-trace RCU updates that fix a number of rare but important race-condition bugs. - Other torture-test updates, most notably better checking of module parameters. In addition, rcutorture may once again be run on CONFIG_PREEMPT_RT kernels. - Torture-test scripting updates, most notably specifying the new CONFIG_KCSAN_STRICT kconfig option rather than maintaining an ever-changing list of individual KCSAN kconfig options. * tag 'rcu.2021.11.01a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (46 commits) rcu: Fix rcu_dynticks_curr_cpu_in_eqs() vs noinstr rcu: Always inline rcu_dynticks_task*_{enter,exit}() torture: Make kvm-remote.sh print size of downloaded tarball torture: Allot 1G of memory for scftorture runs tools/rcu: Add an extract-stall script scftorture: Warn on individual scf_torture_init() error conditions scftorture: Count reschedule IPIs scftorture: Account for weight_resched when checking for all zeroes scftorture: Shut down if nonsensical arguments given scftorture: Allow zero weight to exclude an smp_call_function*() category rcu: Avoid unneeded function call in rcu_read_unlock() rcu-tasks: Update comments to cond_resched_tasks_rcu_qs() rcu-tasks: Fix IPI failure handling in trc_wait_for_one_reader rcu-tasks: Fix read-side primitives comment for call_rcu_tasks_trace rcu-tasks: Clarify read side section info for rcu_tasks_rude GP primitives rcu-tasks: Correct comparisons for CPU numbers in show_stalled_task_trace rcu-tasks: Correct firstreport usage in check_all_holdout_tasks_trace rcu-tasks: Fix s/rcu_add_holdout/trc_add_holdout/ typo in comment rcu-tasks: Move RTGS_WAIT_CBS to beginning of rcu_tasks_kthread() loop rcu-tasks: Fix s/instruction/instructions/ typo in comment ...