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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361// SPDX-License-Identifier: GPL-2.0/* * Task work handling for io_uring */#include <linux/kernel.h>#include <linux/errno.h>#include <linux/sched/signal.h>#include <linux/io_uring.h>#include <linux/indirect_call_wrapper.h>
#include "io_uring.h"#include "tctx.h"#include "poll.h"#include "rw.h"#include "eventfd.h"#include "wait.h"#include "mpscq.h"
static void ctx_flush_and_put(struct io_ring_ctx *ctx, io_tw_token_t tw){ if (!ctx) return; if (ctx->flags & IORING_SETUP_TASKRUN_FLAG) atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
io_submit_flush_completions(ctx); mutex_unlock(&ctx->uring_lock); percpu_ref_put(&ctx->refs);}
void io_tctx_fallback_work(struct work_struct *work){ struct io_uring_task *tctx = container_of(work, struct io_uring_task, fallback_work); unsigned int count = 0;
/* * Run the entries directly. We're in PF_KTHRED context, hence * io_should_terminate_tw() is true and they will be marked as * canceled. */ tctx_task_work_run(tctx, UINT_MAX, &count); put_task_struct(tctx->task);}
static void io_fallback_tw(struct io_uring_task *tctx){ /* * The task ref both keeps ->task valid and, as __io_uring_free() is * only called when the task itself is freed, ensures the tctx (and * the queued work) stay around until the drain has run. */ get_task_struct(tctx->task); if (!queue_work(system_dfl_wq, &tctx->fallback_work)) put_task_struct(tctx->task);}
/* * Run queued task_work, processing no more than max_entries, with the number * of entries processed added to *count. If more entries than max_entries are * available, the remainder simply stay on the queue for the next run. */void tctx_task_work_run(struct io_uring_task *tctx, unsigned int max_entries, unsigned int *count){ struct io_ring_ctx *ctx = NULL; struct io_tw_state ts = { };
while (*count < max_entries) { struct llist_node *node = mpscq_pop(&tctx->task_list, &tctx->task_head); struct io_kiocb *req;
if (!node) { if (mpscq_empty(&tctx->task_list)) break; /* * A producer has published a node but hasn't * linked it into the queue yet (see mpscq_pop()). * Give it a chance to finish rather than spinning, * and don't sit on the ctx lock while doing so. */ ctx_flush_and_put(ctx, ts); ctx = NULL; cond_resched(); continue; } req = container_of(node, struct io_kiocb, io_task_work.node); if (req->ctx != ctx) { ctx_flush_and_put(ctx, ts); ctx = req->ctx; mutex_lock(&ctx->uring_lock); percpu_ref_get(&ctx->refs); ts.cancel = io_should_terminate_tw(ctx); } INDIRECT_CALL_2(req->io_task_work.func, io_poll_task_func, io_req_rw_complete, (struct io_tw_req){req}, ts); (*count)++; /* * Break if most recent pop emptied the queue. This helps * bound task_work run, and also protects the regular * task_work addition. */ if (mpscq_pop_emptied(&tctx->task_list, tctx->task_head)) break; if (unlikely(need_resched())) { ctx_flush_and_put(ctx, ts); ctx = NULL; cond_resched(); } } ctx_flush_and_put(ctx, ts);
/* * Relaxed read is enough as only the task itself sets ->in_cancel. * The tctx may also be drained by io_tctx_fallback_work(), in which * case current is a kworker that has no tctx refs to drop. */ if (unlikely(atomic_read(&tctx->in_cancel)) && current->io_uring == tctx) io_uring_drop_tctx_refs(current);
trace_io_uring_task_work_run(tctx, *count);}
void tctx_task_work(struct callback_head *cb){ struct io_uring_task *tctx; unsigned int count = 0;
tctx = container_of(cb, struct io_uring_task, task_work); tctx_task_work_run(tctx, UINT_MAX, &count);}
/* * Sets IORING_SQ_TASKRUN in the sq_flags shared with userspace, using the * RCU protected rings pointer to be safe against concurrent ring resizing. */static void io_ctx_mark_taskrun(struct io_ring_ctx *ctx){ lockdep_assert_in_rcu_read_lock();
if (ctx->flags & IORING_SETUP_TASKRUN_FLAG) { struct io_rings *rings = rcu_dereference(ctx->rings_rcu);
atomic_or(IORING_SQ_TASKRUN, &rings->sq_flags); }}
void io_req_local_work_add(struct io_kiocb *req, unsigned flags){ struct io_ring_ctx *ctx = req->ctx; int nr_wait;
/* pairs with synchronize_rcu() in io_ring_exit_work() */ guard(rcu)();
/* * We don't know how many requests there are in the link and whether * they can even be queued lazily, fall back to non-lazy. */ if (req->flags & IO_REQ_LINK_FLAGS) flags &= ~IOU_F_TWQ_LAZY_WAKE;
/* * The xchg() in mpscq_push() implies a full barrier, which pairs with * the barrier in set_current_state() on the io_cqring_wait() side. This * ensures that either we see the updated ->cq_wait_nr, or waiters going * to sleep will observe the work added to the list, which is similar to * the wait/wake task state sync. */ if (mpscq_push(&ctx->work_list, &req->io_task_work.node)) { io_ctx_mark_taskrun(ctx); if (data_race(ctx->int_flags) & IO_RING_F_HAS_EVFD) io_eventfd_signal(ctx, false); }
/* * No one is waiting (IO_CQ_WAKE_INIT), or this cycle's wake up has * already been issued (zero or negative, see below). */ nr_wait = atomic_read(&ctx->cq_wait_nr); if (nr_wait <= 0) return; if (flags & IOU_F_TWQ_LAZY_WAKE) { /* * ->cq_wait_nr counts down the number of lazy adds, once it * hits zero we're good to wake the waiter. A producer that * gets delayed between pushing its entry and getting here * may count down a later wait cycle. That's OK, it'll be an * early wake, not a lost one. */ if (!atomic_dec_and_test(&ctx->cq_wait_nr)) return; } else if (atomic_xchg(&ctx->cq_wait_nr, IO_CQ_WAKE_INIT) <= 0) { /* * Potentially raced with lazy add, claim the wake. A value * <= 0 means a lazy add hit zero or another forced add * claimed IO_CQ_WAKE_INIT. Either way, the wake up for this * wait cycle has already been done. */ return; } wake_up_state(ctx->submitter_task, TASK_INTERRUPTIBLE);}
void io_req_normal_work_add(struct io_kiocb *req){ struct io_uring_task *tctx = req->tctx; struct io_ring_ctx *ctx = req->ctx;
/* tw run already pending, nothing else to do */ if (!mpscq_push(&tctx->task_list, &req->io_task_work.node)) return;
/* * Doesn't need to use ->rings_rcu, as resizing isn't supported for * !DEFER_TASKRUN. */ if (ctx->flags & IORING_SETUP_TASKRUN_FLAG) atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
/* SQPOLL doesn't need the task_work added, it'll run it itself */ if (ctx->flags & IORING_SETUP_SQPOLL) { __set_notify_signal(tctx->task); return; }
if (likely(!task_work_add(tctx->task, &tctx->task_work, ctx->notify_method))) return;
io_fallback_tw(tctx);}
void io_req_task_work_add_remote(struct io_kiocb *req, unsigned flags){ if (WARN_ON_ONCE(!(req->ctx->flags & IORING_SETUP_DEFER_TASKRUN))) return; __io_req_task_work_add(req, flags);}
void __cold io_cancel_local_task_work(struct io_ring_ctx *ctx){ struct io_tw_state ts = { .cancel = true }; struct llist_node *node;
/* * The work list consumer side is serialized by ->uring_lock, see * __io_run_local_work(). Grab it to guard against racing with normal * task_work running, as the task may be exiting. The ring is going * away, run the entries in cancel mode right here - the callers * provide the same process context the per-ctx fallback work that * they were previously punted to ran in. */ guard(mutex)(&ctx->uring_lock);
while (!mpscq_empty(&ctx->work_list)) { struct io_kiocb *req;
node = mpscq_pop(&ctx->work_list, &ctx->work_head); if (!node) { /* a producer is mid-push, wait for it to link */ cond_resched(); continue; } req = container_of(node, struct io_kiocb, io_task_work.node); req->io_task_work.func((struct io_tw_req){req}, ts); } io_submit_flush_completions(ctx);}
static bool io_run_local_work_continue(struct io_ring_ctx *ctx, int events, int min_events){ if (!io_local_work_pending(ctx)) return false; if (events < min_events) return true; if (ctx->flags & IORING_SETUP_TASKRUN_FLAG) atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags); return false;}
static int __io_run_local_work_loop(struct io_ring_ctx *ctx, io_tw_token_t tw, int events){ int ret = 0;
while (ret < events) { struct llist_node *node = mpscq_pop(&ctx->work_list, &ctx->work_head); struct io_kiocb *req;
if (!node) break; req = container_of(node, struct io_kiocb, io_task_work.node); INDIRECT_CALL_2(req->io_task_work.func, io_poll_task_func, io_req_rw_complete, (struct io_tw_req){req}, tw); ret++; }
return ret;}
static int __io_run_local_work(struct io_ring_ctx *ctx, io_tw_token_t tw, int min_events, int max_events){ unsigned int loops = 0; int ret = 0;
if (WARN_ON_ONCE(ctx->submitter_task != current)) return -EEXIST; if (ctx->flags & IORING_SETUP_TASKRUN_FLAG) atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);again: /* * If the last loop made no progress while work is still pending, * a producer has published a node but hasn't linked it into the * queue yet (see mpscq_pop()). Give it a chance to finish rather * than spinning on the queue. */ if (unlikely(loops && !ret)) cond_resched(); tw.cancel = io_should_terminate_tw(ctx); min_events -= ret; ret = __io_run_local_work_loop(ctx, tw, max_events); loops++;
if (io_run_local_work_continue(ctx, ret, min_events)) goto again; io_submit_flush_completions(ctx); if (io_run_local_work_continue(ctx, ret, min_events)) goto again;
trace_io_uring_local_work_run(ctx, ret, loops); return ret;}
int io_run_local_work_locked(struct io_ring_ctx *ctx, int min_events){ struct io_tw_state ts = {};
if (!io_local_work_pending(ctx)) return 0; return __io_run_local_work(ctx, ts, min_events, max(IO_LOCAL_TW_DEFAULT_MAX, min_events));}
int io_run_local_work(struct io_ring_ctx *ctx, int min_events, int max_events){ struct io_tw_state ts = {}; int ret;
mutex_lock(&ctx->uring_lock); ret = __io_run_local_work(ctx, ts, min_events, max_events); mutex_unlock(&ctx->uring_lock); return ret;}