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/ts_kmp.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 168 insertions(+) create mode 100644 lib/ts_kmp.c (limited to 'lib/ts_kmp.c') diff --git a/lib/ts_kmp.c b/lib/ts_kmp.c new file mode 100644 index 000000000..29466c180 --- /dev/null +++ b/lib/ts_kmp.c @@ -0,0 +1,168 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * lib/ts_kmp.c Knuth-Morris-Pratt text search implementation + * + * Authors: Thomas Graf + * + * ========================================================================== + * + * Implements a linear-time string-matching algorithm due to Knuth, + * Morris, and Pratt [1]. Their algorithm avoids the explicit + * computation of the transition function DELTA altogether. Its + * matching time is O(n), for n being length(text), using just an + * auxiliary function PI[1..m], for m being length(pattern), + * precomputed from the pattern in time O(m). The array PI allows + * the transition function DELTA to be computed efficiently + * "on the fly" as needed. Roughly speaking, for any state + * "q" = 0,1,...,m and any character "a" in SIGMA, the value + * PI["q"] contains the information that is independent of "a" and + * is needed to compute DELTA("q", "a") [2]. Since the array PI + * has only m entries, whereas DELTA has O(m|SIGMA|) entries, we + * save a factor of |SIGMA| in the preprocessing time by computing + * PI rather than DELTA. + * + * [1] Cormen, Leiserson, Rivest, Stein + * Introdcution to Algorithms, 2nd Edition, MIT Press + * [2] See finite automaton theory + */ + +#include +#include +#include +#include +#include + +struct ts_kmp +{ + u8 * pattern; + unsigned int pattern_len; + unsigned int prefix_tbl[]; +}; + +static unsigned int kmp_find(struct ts_config *conf, struct ts_state *state) +{ + struct ts_kmp *kmp = ts_config_priv(conf); + unsigned int i, q = 0, text_len, consumed = state->offset; + const u8 *text; + const int icase = conf->flags & TS_IGNORECASE; + + for (;;) { + text_len = conf->get_next_block(consumed, &text, conf, state); + + if (unlikely(text_len == 0)) + break; + + for (i = 0; i < text_len; i++) { + while (q > 0 && kmp->pattern[q] + != (icase ? toupper(text[i]) : text[i])) + q = kmp->prefix_tbl[q - 1]; + if (kmp->pattern[q] + == (icase ? toupper(text[i]) : text[i])) + q++; + if (unlikely(q == kmp->pattern_len)) { + state->offset = consumed + i + 1; + return state->offset - kmp->pattern_len; + } + } + + consumed += text_len; + } + + return UINT_MAX; +} + +static inline void compute_prefix_tbl(const u8 *pattern, unsigned int len, + unsigned int *prefix_tbl, int flags) +{ + unsigned int k, q; + const u8 icase = flags & TS_IGNORECASE; + + for (k = 0, q = 1; q < len; q++) { + while (k > 0 && (icase ? toupper(pattern[k]) : pattern[k]) + != (icase ? toupper(pattern[q]) : pattern[q])) + k = prefix_tbl[k-1]; + if ((icase ? toupper(pattern[k]) : pattern[k]) + == (icase ? toupper(pattern[q]) : pattern[q])) + k++; + prefix_tbl[q] = k; + } +} + +static struct ts_config *kmp_init(const void *pattern, unsigned int len, + gfp_t gfp_mask, int flags) +{ + struct ts_config *conf; + struct ts_kmp *kmp; + int i; + unsigned int prefix_tbl_len; + size_t priv_size; + + /* Zero-length patterns would make kmp_find() read beyond kmp->pattern. */ + if (unlikely(!len)) + return ERR_PTR(-EINVAL); + + /* + * kmp->pattern is stored immediately after the prefix_tbl[] table. + * Reject lengths that would wrap while sizing either region. + */ + if (unlikely(check_mul_overflow(len, sizeof(*kmp->prefix_tbl), + &prefix_tbl_len) || + check_add_overflow(sizeof(*kmp), (size_t)len, &priv_size) || + check_add_overflow(priv_size, prefix_tbl_len, &priv_size))) + return ERR_PTR(-EINVAL); + + conf = alloc_ts_config(priv_size, gfp_mask); + if (IS_ERR(conf)) + return conf; + + conf->flags = flags; + kmp = ts_config_priv(conf); + kmp->pattern_len = len; + compute_prefix_tbl(pattern, len, kmp->prefix_tbl, flags); + kmp->pattern = (u8 *) kmp->prefix_tbl + prefix_tbl_len; + if (flags & TS_IGNORECASE) + for (i = 0; i < len; i++) + kmp->pattern[i] = toupper(((u8 *)pattern)[i]); + else + memcpy(kmp->pattern, pattern, len); + + return conf; +} + +static void *kmp_get_pattern(struct ts_config *conf) +{ + struct ts_kmp *kmp = ts_config_priv(conf); + return kmp->pattern; +} + +static unsigned int kmp_get_pattern_len(struct ts_config *conf) +{ + struct ts_kmp *kmp = ts_config_priv(conf); + return kmp->pattern_len; +} + +static struct ts_ops kmp_ops = { + .name = "kmp", + .find = kmp_find, + .init = kmp_init, + .get_pattern = kmp_get_pattern, + .get_pattern_len = kmp_get_pattern_len, + .owner = THIS_MODULE, + .list = LIST_HEAD_INIT(kmp_ops.list) +}; + +static int __init init_kmp(void) +{ + return textsearch_register(&kmp_ops); +} + +static void __exit exit_kmp(void) +{ + textsearch_unregister(&kmp_ops); +} + +MODULE_DESCRIPTION("Knuth-Morris-Pratt text search implementation"); +MODULE_LICENSE("GPL"); + +module_init(init_kmp); +module_exit(exit_kmp); -- cgit v1.3.1