From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- net/rds/page.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 170 insertions(+) create mode 100644 net/rds/page.c (limited to 'net/rds/page.c') diff --git a/net/rds/page.c b/net/rds/page.c new file mode 100644 index 000000000..afb151eac --- /dev/null +++ b/net/rds/page.c @@ -0,0 +1,170 @@ +/* + * Copyright (c) 2006 Oracle. All rights reserved. + * + * This software is available to you under a choice of one of two + * licenses. You may choose to be licensed under the terms of the GNU + * General Public License (GPL) Version 2, available from the file + * COPYING in the main directory of this source tree, or the + * OpenIB.org BSD license below: + * + * Redistribution and use in source and binary forms, with or + * without modification, are permitted provided that the following + * conditions are met: + * + * - Redistributions of source code must retain the above + * copyright notice, this list of conditions and the following + * disclaimer. + * + * - Redistributions in binary form must reproduce the above + * copyright notice, this list of conditions and the following + * disclaimer in the documentation and/or other materials + * provided with the distribution. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + * + */ +#include +#include +#include +#include + +#include "rds.h" + +struct rds_page_remainder { + struct page *r_page; + unsigned long r_offset; + local_lock_t bh_lock; +}; + +static DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders) = { + .bh_lock = INIT_LOCAL_LOCK(bh_lock), +}; + +/** + * rds_page_remainder_alloc - build up regions of a message. + * + * @scat: Scatter list for message + * @bytes: the number of bytes needed. + * @gfp: the waiting behaviour of the allocation + * + * @gfp is always ored with __GFP_HIGHMEM. Callers must be prepared to + * kmap the pages, etc. + * + * If @bytes is at least a full page then this just returns a page from + * alloc_page(). + * + * If @bytes is a partial page then this stores the unused region of the + * page in a per-cpu structure. Future partial-page allocations may be + * satisfied from that cached region. This lets us waste less memory on + * small allocations with minimal complexity. It works because the transmit + * path passes read-only page regions down to devices. They hold a page + * reference until they are done with the region. + */ +int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes, + gfp_t gfp) +{ + struct rds_page_remainder *rem; + struct page *page; + int ret; + + gfp |= __GFP_HIGHMEM; + + /* jump straight to allocation if we're trying for a huge page */ + if (bytes >= PAGE_SIZE) { + page = alloc_page(gfp); + if (!page) { + ret = -ENOMEM; + } else { + sg_set_page(scat, page, PAGE_SIZE, 0); + ret = 0; + } + goto out; + } + + local_bh_disable(); + local_lock_nested_bh(&rds_page_remainders.bh_lock); + rem = this_cpu_ptr(&rds_page_remainders); + + while (1) { + /* avoid a tiny region getting stuck by tossing it */ + if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) { + rds_stats_inc(s_page_remainder_miss); + __free_page(rem->r_page); + rem->r_page = NULL; + } + + /* hand out a fragment from the cached page */ + if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) { + sg_set_page(scat, rem->r_page, bytes, rem->r_offset); + get_page(sg_page(scat)); + + if (rem->r_offset != 0) + rds_stats_inc(s_page_remainder_hit); + + rem->r_offset += ALIGN(bytes, 8); + if (rem->r_offset >= PAGE_SIZE) { + __free_page(rem->r_page); + rem->r_page = NULL; + } + ret = 0; + break; + } + + /* alloc if there is nothing for us to use */ + local_unlock_nested_bh(&rds_page_remainders.bh_lock); + local_bh_enable(); + + page = alloc_page(gfp); + + local_bh_disable(); + local_lock_nested_bh(&rds_page_remainders.bh_lock); + rem = this_cpu_ptr(&rds_page_remainders); + + if (!page) { + ret = -ENOMEM; + break; + } + + /* did someone race to fill the remainder before us? */ + if (rem->r_page) { + __free_page(page); + continue; + } + + /* otherwise install our page and loop around to alloc */ + rem->r_page = page; + rem->r_offset = 0; + } + + local_unlock_nested_bh(&rds_page_remainders.bh_lock); + local_bh_enable(); +out: + rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret, + ret ? NULL : sg_page(scat), ret ? 0 : scat->offset, + ret ? 0 : scat->length); + return ret; +} +EXPORT_SYMBOL_GPL(rds_page_remainder_alloc); + +void rds_page_exit(void) +{ + unsigned int cpu; + + for_each_possible_cpu(cpu) { + struct rds_page_remainder *rem; + + rem = &per_cpu(rds_page_remainders, cpu); + rdsdebug("cpu %u\n", cpu); + + if (rem->r_page) + __free_page(rem->r_page); + rem->r_page = NULL; + } +} -- cgit v1.3.1