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. --- net/sunrpc/timer.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 net/sunrpc/timer.c (limited to 'net/sunrpc/timer.c') diff --git a/net/sunrpc/timer.c b/net/sunrpc/timer.c new file mode 100644 index 000000000..81ae35b37 --- /dev/null +++ b/net/sunrpc/timer.c @@ -0,0 +1,123 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/net/sunrpc/timer.c + * + * Estimate RPC request round trip time. + * + * Based on packet round-trip and variance estimator algorithms described + * in appendix A of "Congestion Avoidance and Control" by Van Jacobson + * and Michael J. Karels (ACM Computer Communication Review; Proceedings + * of the Sigcomm '88 Symposium in Stanford, CA, August, 1988). + * + * This RTT estimator is used only for RPC over datagram protocols. + * + * Copyright (C) 2002 Trond Myklebust + */ + +#include + +#include +#include +#include + +#include + +#define RPC_RTO_MAX (60*HZ) +#define RPC_RTO_INIT (HZ/5) +#define RPC_RTO_MIN (HZ/10) + +/** + * rpc_init_rtt - Initialize an RPC RTT estimator context + * @rt: context to initialize + * @timeo: initial timeout value, in jiffies + * + */ +void rpc_init_rtt(struct rpc_rtt *rt, unsigned long timeo) +{ + unsigned long init = 0; + unsigned int i; + + rt->timeo = timeo; + + if (timeo > RPC_RTO_INIT) + init = (timeo - RPC_RTO_INIT) << 3; + for (i = 0; i < 5; i++) { + rt->srtt[i] = init; + rt->sdrtt[i] = RPC_RTO_INIT; + rt->ntimeouts[i] = 0; + } +} +EXPORT_SYMBOL_GPL(rpc_init_rtt); + +/** + * rpc_update_rtt - Update an RPC RTT estimator context + * @rt: context to update + * @timer: timer array index (request type) + * @m: recent actual RTT, in jiffies + * + * NB: When computing the smoothed RTT and standard deviation, + * be careful not to produce negative intermediate results. + */ +void rpc_update_rtt(struct rpc_rtt *rt, unsigned int timer, long m) +{ + long *srtt, *sdrtt; + + if (timer-- == 0) + return; + + /* jiffies wrapped; ignore this one */ + if (m < 0) + return; + + if (m == 0) + m = 1L; + + srtt = (long *)&rt->srtt[timer]; + m -= *srtt >> 3; + *srtt += m; + + if (m < 0) + m = -m; + + sdrtt = (long *)&rt->sdrtt[timer]; + m -= *sdrtt >> 2; + *sdrtt += m; + + /* Set lower bound on the variance */ + if (*sdrtt < RPC_RTO_MIN) + *sdrtt = RPC_RTO_MIN; +} +EXPORT_SYMBOL_GPL(rpc_update_rtt); + +/** + * rpc_calc_rto - Provide an estimated timeout value + * @rt: context to use for calculation + * @timer: timer array index (request type) + * + * Estimate RTO for an NFS RPC sent via an unreliable datagram. Use + * the mean and mean deviation of RTT for the appropriate type of RPC + * for frequently issued RPCs, and a fixed default for the others. + * + * The justification for doing "other" this way is that these RPCs + * happen so infrequently that timer estimation would probably be + * stale. Also, since many of these RPCs are non-idempotent, a + * conservative timeout is desired. + * + * getattr, lookup, + * read, write, commit - A+4D + * other - timeo + */ +unsigned long rpc_calc_rto(struct rpc_rtt *rt, unsigned int timer) +{ + unsigned long res; + + if (timer-- == 0) + return rt->timeo; + + res = ((rt->srtt[timer] + 7) >> 3) + rt->sdrtt[timer]; + if (res > RPC_RTO_MAX) + res = RPC_RTO_MAX; + + return res; +} +EXPORT_SYMBOL_GPL(rpc_calc_rto); -- cgit v1.3.1