From 9cc63f8bcd560c760d0b12e15bba8f81c86237cf Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 14 Aug 2026 15:43:51 -0700 Subject: Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEAD Changes: Make expedited grace periods expedite normal RCU callbacks Miscellaneous fixes: * Improve diagnostic output with character task states. * Mark accesses to inform KCSAN of concurrency design. * Move from kmalloc() to kmalloc_obj(). * Documentation updates. * Improve handling of RCU deferred quiescent states. * Clean up unused function arguments and structure fields. * Reduce show_rcu_gp_kthreads() stack space. Tasks RCU updates: * Clean up after SRCU re-implementation of Tasks Trace RCU. * Mark accesses to inform KCSAN of concurrency design. * Add ->lazy_timer status to diagnostic output. * Remove an unnecessary memory barrier. * Fix a data race, courtesy of KCSAN. * Documentation updates. * Convert cond_resched_tasks_rcu_qs() from macro to static inline function. SRCU updates: * Add Rust helpers for SRCU. * Avoid losing queued work at cleanup_srcu_struct() time. Torture-test updates: * Preparation work for immediate RCU priority deboosting. * Test RCU readers from real interrupt handlers (as opposed to softirq). * Simplify code through use of cpumask_next_wrap(). * Improve diagnostic output with character task states. * Add rcutorture.nwriters parameter to allow lightweight stall testing, and rcutorture.stall_only to make doing so easier. * Test an RCU Tasks Trace grace period implying an RCU grace period. * Make RCU Tasks Trace torturing track reader batches. * Fix a data race, courtesy of KCSAN. * Plug a shuffle_tmp_mask memory leak on kthread spawn failure. --- lib/percpu_test.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 148 insertions(+) create mode 100644 lib/percpu_test.c (limited to 'lib/percpu_test.c') diff --git a/lib/percpu_test.c b/lib/percpu_test.c new file mode 100644 index 000000000..ce7124b16 --- /dev/null +++ b/lib/percpu_test.c @@ -0,0 +1,148 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include + +/* validate @native and @pcp counter values match @expected */ +#define CHECK(native, pcp, expected) \ + do { \ + WARN((native) != (expected), \ + "raw %ld (0x%lx) != expected %lld (0x%llx)", \ + (native), (native), \ + (long long)(expected), (long long)(expected)); \ + WARN(__this_cpu_read(pcp) != (expected), \ + "pcp %ld (0x%lx) != expected %lld (0x%llx)", \ + __this_cpu_read(pcp), __this_cpu_read(pcp), \ + (long long)(expected), (long long)(expected)); \ + } while (0) + +static DEFINE_PER_CPU(long, long_counter); +static DEFINE_PER_CPU(unsigned long, ulong_counter); + +static int __init percpu_test_init(void) +{ + /* + * volatile prevents compiler from optimizing it uses, otherwise the + * +ul_one/-ul_one below would replace with inc/dec instructions. + */ + volatile unsigned int ui_one = 1; + unsigned long long ull = 0; + unsigned long ul = 0; + long l = 0; + + pr_info("percpu test start\n"); + + preempt_disable(); + + l += -1; + __this_cpu_add(long_counter, -1); + CHECK(l, long_counter, -1); + + l += 1; + __this_cpu_add(long_counter, 1); + CHECK(l, long_counter, 0); + + ul = 0; + __this_cpu_write(ulong_counter, 0); + + ul += 1UL; + __this_cpu_add(ulong_counter, 1UL); + CHECK(ul, ulong_counter, 1); + + ul += -1UL; + __this_cpu_add(ulong_counter, -1UL); + CHECK(ul, ulong_counter, 0); + + ul += -(unsigned long)1; + __this_cpu_add(ulong_counter, -(unsigned long)1); + CHECK(ul, ulong_counter, -1); + + ul = 0; + __this_cpu_write(ulong_counter, 0); + + ul -= 1; + __this_cpu_dec(ulong_counter); + CHECK(ul, ulong_counter, -1); + CHECK(ul, ulong_counter, ULONG_MAX); + + l += -ui_one; + __this_cpu_add(long_counter, -ui_one); + CHECK(l, long_counter, 0xffffffff); + + l += ui_one; + __this_cpu_add(long_counter, ui_one); + CHECK(l, long_counter, (long)0x100000000LL); + + + l = 0; + __this_cpu_write(long_counter, 0); + + l -= ui_one; + __this_cpu_sub(long_counter, ui_one); + CHECK(l, long_counter, -1); + + l = 0; + __this_cpu_write(long_counter, 0); + + l += ui_one; + __this_cpu_add(long_counter, ui_one); + CHECK(l, long_counter, 1); + + l += -ui_one; + __this_cpu_add(long_counter, -ui_one); + CHECK(l, long_counter, (long)0x100000000LL); + + l = 0; + __this_cpu_write(long_counter, 0); + + l -= ui_one; + this_cpu_sub(long_counter, ui_one); + CHECK(l, long_counter, -1); + CHECK(l, long_counter, ULONG_MAX); + + ul = 0; + __this_cpu_write(ulong_counter, 0); + + ul += ui_one; + __this_cpu_add(ulong_counter, ui_one); + CHECK(ul, ulong_counter, 1); + + ul = 0; + __this_cpu_write(ulong_counter, 0); + + ul -= ui_one; + __this_cpu_sub(ulong_counter, ui_one); + CHECK(ul, ulong_counter, -1); + CHECK(ul, ulong_counter, ULONG_MAX); + + ul = ull = 0; + __this_cpu_write(ulong_counter, 0); + + ul = ull += UINT_MAX; + __this_cpu_add(ulong_counter, ull); + CHECK(ul, ulong_counter, UINT_MAX); + + ul = 3; + __this_cpu_write(ulong_counter, 3); + + ul = this_cpu_sub_return(ulong_counter, ui_one); + CHECK(ul, ulong_counter, 2); + + ul = __this_cpu_sub_return(ulong_counter, ui_one); + CHECK(ul, ulong_counter, 1); + + preempt_enable(); + + pr_info("percpu test done\n"); + return -EAGAIN; /* Fail will directly unload the module */ +} + +static void __exit percpu_test_exit(void) +{ +} + +module_init(percpu_test_init) +module_exit(percpu_test_exit) + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Greg Thelen"); +MODULE_DESCRIPTION("percpu operations test"); -- cgit v1.3.1