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io.cfa @ 561dd26

ADTarm-ehast-experimentalenumforall-pointer-decayjacob/cs343-translationnew-ast-unique-exprpthread-emulationqualifiedEnum

Last change on this file since 561dd26 was ece0e80, checked in by Thierry Delisle <tdelisle@…>, 3 years ago
Added prints. Naive implementation of cancel. Server now shutdown cleanly.
Property mode set to `100644`
File size: 16.8 KB

Rev	Line
[ecf6b46]	1	//
	2	// Cforall Version 1.0.0 Copyright (C) 2020 University of Waterloo
	3	//
	4	// The contents of this file are covered under the licence agreement in the
	5	// file "LICENCE" distributed with Cforall.
	6	//
	7	// io.cfa --
	8	//
	9	// Author : Thierry Delisle
	10	// Created On : Thu Apr 23 17:31:00 2020
	11	// Last Modified By :
	12	// Last Modified On :
	13	// Update Count :
	14	//
	15
[3e2b9c9]	16	#define __cforall_thread__
	17
[20ab637]	18	#if defined(__CFA_DEBUG__)
	19	// #define __CFA_DEBUG_PRINT_IO__
[e660761]	20	// #define __CFA_DEBUG_PRINT_IO_CORE__
[20ab637]	21	#endif
[4069faad]	22
[f6660520]	23
[3e2b9c9]	24	#if defined(CFA_HAVE_LINUX_IO_URING_H)
[31bb2e1]	25	#define _GNU_SOURCE /* See feature_test_macros(7) */
	26	#include <errno.h>
[3e2b9c9]	27	#include <signal.h>
[31bb2e1]	28	#include <stdint.h>
	29	#include <string.h>
	30	#include <unistd.h>
	31
[92976d9]	32	extern "C" {
[f00b26d4]	33	#include <sys/epoll.h>
[92976d9]	34	#include <sys/syscall.h>
	35
	36	#include <linux/io_uring.h>
	37	}
	38
[3e2b9c9]	39	#include "stats.hfa"
	40	#include "kernel.hfa"
	41	#include "kernel/fwd.hfa"
	42	#include "io/types.hfa"
[185efe6]	43
[2fafe7e]	44	// returns true of acquired as leader or second leader
	45	static inline bool try_lock( __leaderlock_t & this ) {
	46	const uintptr_t thrd = 1z \| (uintptr_t)active_thread();
	47	bool block;
	48	disable_interrupts();
	49	for() {
	50	struct $thread * expected = this.value;
	51	if( 1p != expected && 0p != expected ) {
	52	/* paranoid */ verify( thrd != (uintptr_t)expected ); // We better not already be the next leader
	53	enable_interrupts( __cfaabi_dbg_ctx );
	54	return false;
	55	}
	56	struct $thread * desired;
	57	if( 0p == expected ) {
	58	// If the lock isn't locked acquire it, no need to block
	59	desired = 1p;
	60	block = false;
	61	}
	62	else {
	63	// If the lock is already locked try becomming the next leader
	64	desired = (struct $thread *)thrd;
	65	block = true;
	66	}
	67	if( __atomic_compare_exchange_n(&this.value, &expected, desired, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ) break;
	68	}
	69	if( block ) {
	70	enable_interrupts( __cfaabi_dbg_ctx );
[e235429]	71	park();
[2fafe7e]	72	disable_interrupts();
	73	}
	74	return true;
	75	}
	76
	77	static inline bool next( __leaderlock_t & this ) {
[8fc652e0]	78	/* paranoid */ verify( ! __preemption_enabled() );
[2fafe7e]	79	struct $thread * nextt;
	80	for() {
	81	struct $thread * expected = this.value;
	82	/* paranoid */ verify( (1 & (uintptr_t)expected) == 1 ); // The lock better be locked
	83
	84	struct $thread * desired;
	85	if( 1p == expected ) {
	86	// No next leader, just unlock
	87	desired = 0p;
	88	nextt = 0p;
	89	}
	90	else {
	91	// There is a next leader, remove but keep locked
	92	desired = 1p;
	93	nextt = (struct $thread *)(~1z & (uintptr_t)expected);
	94	}
	95	if( __atomic_compare_exchange_n(&this.value, &expected, desired, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ) break;
	96	}
	97
	98	if(nextt) {
[b4b63e8]	99	unpark( nextt );
[2fafe7e]	100	enable_interrupts( __cfaabi_dbg_ctx );
	101	return true;
	102	}
	103	enable_interrupts( __cfaabi_dbg_ctx );
	104	return false;
	105	}
	106
[92976d9]	107	//=============================================================================================
[3e2b9c9]	108	// I/O Syscall
[92976d9]	109	//=============================================================================================
[3e2b9c9]	110	static int __io_uring_enter( struct __io_data & ring, unsigned to_submit, bool get ) {
[20ab637]	111	bool need_sys_to_submit = false;
	112	bool need_sys_to_complete = false;
	113	unsigned flags = 0;
	114
	115	TO_SUBMIT:
	116	if( to_submit > 0 ) {
	117	if( !(ring.ring_flags & IORING_SETUP_SQPOLL) ) {
	118	need_sys_to_submit = true;
	119	break TO_SUBMIT;
	120	}
	121	if( (*ring.submit_q.flags) & IORING_SQ_NEED_WAKEUP ) {
	122	need_sys_to_submit = true;
	123	flags \|= IORING_ENTER_SQ_WAKEUP;
	124	}
	125	}
	126
	127	if( get && !(ring.ring_flags & IORING_SETUP_SQPOLL) ) {
	128	flags \|= IORING_ENTER_GETEVENTS;
	129	if( (ring.ring_flags & IORING_SETUP_IOPOLL) ) {
	130	need_sys_to_complete = true;
	131	}
	132	}
	133
	134	int ret = 0;
	135	if( need_sys_to_submit \|\| need_sys_to_complete ) {
[ece0e80]	136	__cfadbg_print_safe(io_core, "Kernel I/O : IO_URING enter %d %u %u\n", ring.fd, to_submit, flags);
[b982fb2]	137	ret = syscall( __NR_io_uring_enter, ring.fd, to_submit, 0, flags, (sigset_t *)0p, _NSIG / 8);
[20ab637]	138	if( ret < 0 ) {
	139	switch((int)errno) {
	140	case EAGAIN:
	141	case EINTR:
	142	ret = -1;
	143	break;
	144	default:
	145	abort( "KERNEL ERROR: IO_URING SYSCALL - (%d) %s\n", (int)errno, strerror(errno) );
	146	}
	147	}
	148	}
	149
	150	// Memory barrier
	151	__atomic_thread_fence( __ATOMIC_SEQ_CST );
	152	return ret;
	153	}
	154
[92976d9]	155	//=============================================================================================
	156	// I/O Polling
	157	//=============================================================================================
[1d5e4711]	158	static unsigned __collect_submitions( struct __io_data & ring );
[4998155]	159	static __u32 __release_consumed_submission( struct __io_data & ring );
[1d5e4711]	160
[f00b26d4]	161	static inline void process(struct io_uring_cqe & cqe ) {
[c402739f]	162	struct io_future_t * future = (struct io_future_t *)(uintptr_t)cqe.user_data;
[fe9468e2]	163	__cfadbg_print_safe( io, "Kernel I/O : Syscall completed : cqe %p, result %d for %p\n", &cqe, cqe.res, future );
[5751a56]	164
[c402739f]	165	fulfil( *future, cqe.res );
[5751a56]	166	}
	167
[92976d9]	168	// Process a single completion message from the io_uring
	169	// This is NOT thread-safe
[f00b26d4]	170	static [int, bool] __drain_io( & struct __io_data ring ) {
[8fc652e0]	171	/* paranoid */ verify( ! __preemption_enabled() );
[e46c753]	172
[5dadc9b]	173	unsigned to_submit = 0;
[f00b26d4]	174	if( ring.poller_submits ) {
[5dadc9b]	175	// If the poller thread also submits, then we need to aggregate the submissions which are ready
[e46c753]	176	to_submit = __collect_submitions( ring );
[5dadc9b]	177	}
	178
[f00b26d4]	179	int ret = __io_uring_enter(ring, to_submit, true);
[20ab637]	180	if( ret < 0 ) {
	181	return [0, true];
	182	}
[1d5e4711]	183
[20ab637]	184	// update statistics
	185	if (to_submit > 0) {
[1d5e4711]	186	__STATS__( true,
	187	if( to_submit > 0 ) {
	188	io.submit_q.submit_avg.rdy += to_submit;
	189	io.submit_q.submit_avg.csm += ret;
	190	io.submit_q.submit_avg.cnt += 1;
	191	}
	192	)
[6f121b8]	193	}
	194
[20ab637]	195	// Release the consumed SQEs
	196	__release_consumed_submission( ring );
[6f121b8]	197
[d384787]	198	// Drain the queue
[92976d9]	199	unsigned head = *ring.completion_q.head;
[6f121b8]	200	unsigned tail = *ring.completion_q.tail;
[4998155]	201	const __u32 mask = *ring.completion_q.mask;
[6f121b8]	202
[d384787]	203	// Nothing was new return 0
	204	if (head == tail) {
[e46c753]	205	return [0, to_submit > 0];
[d384787]	206	}
[92976d9]	207
[4998155]	208	__u32 count = tail - head;
[1d5e4711]	209	/* paranoid */ verify( count != 0 );
[d384787]	210	for(i; count) {
[6f121b8]	211	unsigned idx = (head + i) & mask;
[d384787]	212	struct io_uring_cqe & cqe = ring.completion_q.cqes[idx];
[92976d9]	213
[d384787]	214	/* paranoid */ verify(&cqe);
[92976d9]	215
[f00b26d4]	216	process( cqe );
[d384787]	217	}
[2d8f7b0]	218
[92976d9]	219	// Mark to the kernel that the cqe has been seen
	220	// Ensure that the kernel only sees the new value of the head index after the CQEs have been read.
[6f121b8]	221	__atomic_thread_fence( __ATOMIC_SEQ_CST );
[d384787]	222	__atomic_fetch_add( ring.completion_q.head, count, __ATOMIC_RELAXED );
[92976d9]	223
[5dadc9b]	224	return [count, count > 0 \|\| to_submit > 0];
[92976d9]	225	}
	226
[f00b26d4]	227	void main( $io_ctx_thread & this ) {
	228	epoll_event ev;
[3e2b9c9]	229	__ioctx_register( this, ev );
[1539bbd]	230
[f00b26d4]	231	__cfadbg_print_safe(io_core, "Kernel I/O : IO poller %p for ring %p ready\n", &this, &this.ring);
[1539bbd]	232
[ece0e80]	233	const int reset_cnt = 5;
	234	int reset = reset_cnt;
[61dd73d]	235	// Then loop until we need to start
[ece0e80]	236	LOOP:
[f00b26d4]	237	while(!__atomic_load_n(&this.done, __ATOMIC_SEQ_CST)) {
[61dd73d]	238	// Drain the io
[5dadc9b]	239	int count;
	240	bool again;
[13c5e19]	241	disable_interrupts();
[f00b26d4]	242	[count, again] = __drain_io( *this.ring );
[5dadc9b]	243
[ece0e80]	244	if(!again) reset--;
[3c039b0]	245
[13c5e19]	246	// Update statistics
[47746a2]	247	__STATS__( true,
	248	io.complete_q.completed_avg.val += count;
[dcb5f8d]	249	io.complete_q.completed_avg.cnt += 1;
[47746a2]	250	)
[13c5e19]	251	enable_interrupts( __cfaabi_dbg_ctx );
[3c039b0]	252
[5dadc9b]	253	// If we got something, just yield and check again
[ece0e80]	254	if(reset > 1) {
[61dd73d]	255	yield();
[ece0e80]	256	continue LOOP;
[61dd73d]	257	}
[ece0e80]	258
	259	// We alread failed to find events a few time.
	260	if(reset == 1) {
	261	// Rearm the context so it can block
	262	// but don't block right away
	263	// we need to retry one last time in case
	264	// something completed just now
	265	__ioctx_prepare_block( this, ev );
	266	continue LOOP;
	267	}
	268
[93526ef]	269	__STATS__( false,
[dcb5f8d]	270	io.complete_q.blocks += 1;
	271	)
[f00b26d4]	272	__cfadbg_print_safe(io_core, "Kernel I/O : Parking io poller %p\n", &this.self);
[5dadc9b]	273
[3e2b9c9]	274	// block this thread
[f00b26d4]	275	wait( this.sem );
[ece0e80]	276
	277	// restore counter
	278	reset = reset_cnt;
[f6660520]	279	}
[61dd73d]	280
	281	__cfadbg_print_safe(io_core, "Kernel I/O : Fast poller for ring %p stopping\n", &this.ring);
	282	}
[f6660520]	283
[92976d9]	284	//=============================================================================================
	285	// I/O Submissions
	286	//=============================================================================================
	287
[2d8f7b0]	288	// Submition steps :
[e46c753]	289	// 1 - Allocate a queue entry. The ring already has memory for all entries but only the ones
[2d8f7b0]	290	// listed in sq.array are visible by the kernel. For those not listed, the kernel does not
	291	// offer any assurance that an entry is not being filled by multiple flags. Therefore, we
	292	// need to write an allocator that allows allocating concurrently.
	293	//
[e46c753]	294	// 2 - Actually fill the submit entry, this is the only simple and straightforward step.
[2d8f7b0]	295	//
[e46c753]	296	// 3 - Append the entry index to the array and adjust the tail accordingly. This operation
[2d8f7b0]	297	// needs to arrive to two concensus at the same time:
	298	// A - The order in which entries are listed in the array: no two threads must pick the
	299	// same index for their entries
	300	// B - When can the tail be update for the kernel. EVERY entries in the array between
	301	// head and tail must be fully filled and shouldn't ever be touched again.
	302	//
	303
[4998155]	304	[* struct io_uring_sqe, __u32] __submit_alloc( struct __io_data & ring, __u64 data ) {
[e46c753]	305	/* paranoid */ verify( data != 0 );
[13c5e19]	306
[6f121b8]	307	// Prepare the data we need
	308	__attribute((unused)) int len = 0;
	309	__attribute((unused)) int block = 0;
[4998155]	310	__u32 cnt = *ring.submit_q.num;
	311	__u32 mask = *ring.submit_q.mask;
[8ae4165]	312
[fe9468e2]	313	__u32 off = thread_rand();
[6f121b8]	314
	315	// Loop around looking for an available spot
[13c5e19]	316	for() {
[6f121b8]	317	// Look through the list starting at some offset
	318	for(i; cnt) {
[4998155]	319	__u64 expected = 0;
	320	__u32 idx = (i + off) & mask;
[6f121b8]	321	struct io_uring_sqe * sqe = &ring.submit_q.sqes[idx];
[4998155]	322	volatile __u64 * udata = &sqe->user_data;
[6f121b8]	323
	324	if( *udata == expected &&
	325	__atomic_compare_exchange_n( udata, &expected, data, true, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED ) )
	326	{
	327	// update statistics
[47746a2]	328	__STATS__( false,
	329	io.submit_q.alloc_avg.val += len;
	330	io.submit_q.alloc_avg.block += block;
	331	io.submit_q.alloc_avg.cnt += 1;
	332	)
[6f121b8]	333
[ece0e80]	334	__cfadbg_print_safe( io, "Kernel I/O : allocated [%p, %u] for %p (%p)\n", sqe, idx, active_thread(), (void*)data );
[13c5e19]	335
[6f121b8]	336	// Success return the data
	337	return [sqe, idx];
	338	}
	339	verify(expected != data);
[2489d31]	340
[6f121b8]	341	len ++;
	342	}
[2489d31]	343
[6f121b8]	344	block++;
	345	yield();
	346	}
[2489d31]	347	}
	348
[4998155]	349	static inline __u32 __submit_to_ready_array( struct __io_data & ring, __u32 idx, const __u32 mask ) {
[df40a56]	350	/* paranoid */ verify( idx <= mask );
	351	/* paranoid */ verify( idx != -1ul32 );
	352
	353	// We need to find a spot in the ready array
	354	__attribute((unused)) int len = 0;
	355	__attribute((unused)) int block = 0;
[4998155]	356	__u32 ready_mask = ring.submit_q.ready_cnt - 1;
[df40a56]	357
[fe9468e2]	358	__u32 off = thread_rand();
[df40a56]	359
[4998155]	360	__u32 picked;
[df40a56]	361	LOOKING: for() {
	362	for(i; ring.submit_q.ready_cnt) {
	363	picked = (i + off) & ready_mask;
[4998155]	364	__u32 expected = -1ul32;
[df40a56]	365	if( __atomic_compare_exchange_n( &ring.submit_q.ready[picked], &expected, idx, true, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED ) ) {
	366	break LOOKING;
	367	}
	368	verify(expected != idx);
	369
	370	len ++;
	371	}
	372
	373	block++;
[2fafe7e]	374
	375	__u32 released = __release_consumed_submission( ring );
	376	if( released == 0 ) {
[34b61882]	377	yield();
	378	}
[df40a56]	379	}
	380
	381	// update statistics
[47746a2]	382	__STATS__( false,
	383	io.submit_q.look_avg.val += len;
	384	io.submit_q.look_avg.block += block;
	385	io.submit_q.look_avg.cnt += 1;
	386	)
[df40a56]	387
	388	return picked;
	389	}
	390
[4998155]	391	void __submit( struct io_context * ctx, __u32 idx ) __attribute__((nonnull (1))) {
[ece0e80]	392	__cfadbg_print_safe( io, "Kernel I/O : submitting %u for %p\n", idx, active_thread() );
	393
[f00b26d4]	394	__io_data & ring = *ctx->thrd.ring;
[5dadc9b]	395	// Get now the data we definetely need
[4998155]	396	volatile __u32 * const tail = ring.submit_q.tail;
	397	const __u32 mask = *ring.submit_q.mask;
[2489d31]	398
[5dadc9b]	399	// There are 2 submission schemes, check which one we are using
[f00b26d4]	400	if( ring.poller_submits ) {
[5dadc9b]	401	// If the poller thread submits, then we just need to add this to the ready array
[df40a56]	402	__submit_to_ready_array( ring, idx, mask );
[5dadc9b]	403
[f00b26d4]	404	post( ctx->thrd.sem );
[5dadc9b]	405
[dd4e2d7]	406	__cfadbg_print_safe( io, "Kernel I/O : Added %u to ready for %p\n", idx, active_thread() );
[2d8f7b0]	407	}
[f00b26d4]	408	else if( ring.eager_submits ) {
[4998155]	409	__u32 picked = __submit_to_ready_array( ring, idx, mask );
[e46c753]	410
[2fafe7e]	411	#if defined(LEADER_LOCK)
	412	if( !try_lock(ring.submit_q.submit_lock) ) {
[47746a2]	413	__STATS__( false,
	414	io.submit_q.helped += 1;
	415	)
[e46c753]	416	return;
	417	}
[8fc652e0]	418	/* paranoid */ verify( ! __preemption_enabled() );
[2fafe7e]	419	__STATS__( true,
	420	io.submit_q.leader += 1;
	421	)
	422	#else
	423	for() {
	424	yield();
	425
	426	if( try_lock(ring.submit_q.submit_lock __cfaabi_dbg_ctx2) ) {
	427	__STATS__( false,
	428	io.submit_q.leader += 1;
	429	)
	430	break;
	431	}
	432
	433	// If some one else collected our index, we are done
	434	#warning ABA problem
	435	if( ring.submit_q.ready[picked] != idx ) {
	436	__STATS__( false,
	437	io.submit_q.helped += 1;
	438	)
	439	return;
	440	}
[e46c753]	441
[47746a2]	442	__STATS__( false,
[2fafe7e]	443	io.submit_q.busy += 1;
[47746a2]	444	)
[e46c753]	445	}
[2fafe7e]	446	#endif
[e46c753]	447
	448	// We got the lock
[be36ec3]	449	// Collect the submissions
[e46c753]	450	unsigned to_submit = __collect_submitions( ring );
	451
[be36ec3]	452	// Actually submit
	453	int ret = __io_uring_enter( ring, to_submit, false );
[309d814]	454
[2fafe7e]	455	#if defined(LEADER_LOCK)
[8fc652e0]	456	/* paranoid */ verify( ! __preemption_enabled() );
[2fafe7e]	457	next(ring.submit_q.submit_lock);
	458	#else
	459	unlock(ring.submit_q.submit_lock);
	460	#endif
[ece0e80]	461	if( ret < 0 ) {
	462	return;
	463	}
[e46c753]	464
	465	// Release the consumed SQEs
[34b61882]	466	__release_consumed_submission( ring );
[e46c753]	467
	468	// update statistics
[be36ec3]	469	__STATS__( false,
[47746a2]	470	io.submit_q.submit_avg.rdy += to_submit;
	471	io.submit_q.submit_avg.csm += ret;
	472	io.submit_q.submit_avg.cnt += 1;
	473	)
[ece0e80]	474
	475	__cfadbg_print_safe( io, "Kernel I/O : submitted %u (among %u) for %p\n", idx, ret, active_thread() );
[e46c753]	476	}
[5dadc9b]	477	else {
	478	// get mutual exclusion
[2fafe7e]	479	#if defined(LEADER_LOCK)
	480	while(!try_lock(ring.submit_q.submit_lock));
	481	#else
	482	lock(ring.submit_q.submit_lock __cfaabi_dbg_ctx2);
	483	#endif
[2489d31]	484
[20ab637]	485	/* paranoid */ verifyf( ring.submit_q.sqes[ idx ].user_data != 0,
	486	/* paranoid */ "index %u already reclaimed\n"
	487	/* paranoid */ "head %u, prev %u, tail %u\n"
	488	/* paranoid */ "[-0: %u,-1: %u,-2: %u,-3: %u]\n",
	489	/* paranoid */ idx,
	490	/* paranoid / ring.submit_q.head, ring.submit_q.prev_head, *tail
	491	/* paranoid / ,ring.submit_q.array[ ((ring.submit_q.head) - 0) & (*ring.submit_q.mask) ]
	492	/* paranoid / ,ring.submit_q.array[ ((ring.submit_q.head) - 1) & (*ring.submit_q.mask) ]
	493	/* paranoid / ,ring.submit_q.array[ ((ring.submit_q.head) - 2) & (*ring.submit_q.mask) ]
	494	/* paranoid / ,ring.submit_q.array[ ((ring.submit_q.head) - 3) & (*ring.submit_q.mask) ]
	495	/* paranoid */ );
	496
[5dadc9b]	497	// Append to the list of ready entries
	498
	499	/* paranoid */ verify( idx <= mask );
[20ab637]	500	ring.submit_q.array[ (*tail) & mask ] = idx;
[5dadc9b]	501	__atomic_fetch_add(tail, 1ul32, __ATOMIC_SEQ_CST);
[d384787]	502
[5dadc9b]	503	// Submit however, many entries need to be submitted
[f00b26d4]	504	int ret = __io_uring_enter( ring, 1, false );
[5dadc9b]	505	if( ret < 0 ) {
	506	switch((int)errno) {
	507	default:
	508	abort( "KERNEL ERROR: IO_URING SUBMIT - %s\n", strerror(errno) );
	509	}
	510	}
[d384787]	511
[5dadc9b]	512	// update statistics
[47746a2]	513	__STATS__( false,
	514	io.submit_q.submit_avg.csm += 1;
	515	io.submit_q.submit_avg.cnt += 1;
	516	)
[5dadc9b]	517
[34b61882]	518	// Release the consumed SQEs
	519	__release_consumed_submission( ring );
[7bfc849]	520
[2fafe7e]	521	#if defined(LEADER_LOCK)
	522	next(ring.submit_q.submit_lock);
	523	#else
	524	unlock(ring.submit_q.submit_lock);
	525	#endif
[dd4e2d7]	526
	527	__cfadbg_print_safe( io, "Kernel I/O : Performed io_submit for %p, returned %d\n", active_thread(), ret );
[5dadc9b]	528	}
[2489d31]	529	}
[e46c753]	530
[d2b5d2d]	531	// #define PARTIAL_SUBMIT 32
[e46c753]	532	static unsigned __collect_submitions( struct __io_data & ring ) {
	533	/* paranoid */ verify( ring.submit_q.ready != 0p );
	534	/* paranoid */ verify( ring.submit_q.ready_cnt > 0 );
	535
	536	unsigned to_submit = 0;
[4998155]	537	__u32 tail = *ring.submit_q.tail;
	538	const __u32 mask = *ring.submit_q.mask;
[1095ccd]	539	#if defined(PARTIAL_SUBMIT)
	540	#if defined(LEADER_LOCK)
	541	#error PARTIAL_SUBMIT and LEADER_LOCK cannot co-exist
	542	#endif
	543	const __u32 cnt = ring.submit_q.ready_cnt > PARTIAL_SUBMIT ? PARTIAL_SUBMIT : ring.submit_q.ready_cnt;
	544	const __u32 offset = ring.submit_q.prev_ready;
	545	ring.submit_q.prev_ready += cnt;
	546	#else
	547	const __u32 cnt = ring.submit_q.ready_cnt;
	548	const __u32 offset = 0;
	549	#endif
[e46c753]	550
	551	// Go through the list of ready submissions
[1095ccd]	552	for( c; cnt ) {
	553	__u32 i = (offset + c) % ring.submit_q.ready_cnt;
	554
[e46c753]	555	// replace any submission with the sentinel, to consume it.
[4998155]	556	__u32 idx = __atomic_exchange_n( &ring.submit_q.ready[i], -1ul32, __ATOMIC_RELAXED);
[e46c753]	557
	558	// If it was already the sentinel, then we are done
	559	if( idx == -1ul32 ) continue;
	560
	561	// If we got a real submission, append it to the list
	562	ring.submit_q.array[ (tail + to_submit) & mask ] = idx & mask;
	563	to_submit++;
	564	}
	565
	566	// Increment the tail based on how many we are ready to submit
	567	__atomic_fetch_add(ring.submit_q.tail, to_submit, __ATOMIC_SEQ_CST);
	568
	569	return to_submit;
	570	}
[34b61882]	571
[4998155]	572	static __u32 __release_consumed_submission( struct __io_data & ring ) {
	573	const __u32 smask = *ring.submit_q.mask;
[732b406]	574
	575	if( !try_lock(ring.submit_q.release_lock __cfaabi_dbg_ctx2) ) return 0;
[4998155]	576	__u32 chead = *ring.submit_q.head;
	577	__u32 phead = ring.submit_q.prev_head;
[34b61882]	578	ring.submit_q.prev_head = chead;
[732b406]	579	unlock(ring.submit_q.release_lock);
	580
[4998155]	581	__u32 count = chead - phead;
[34b61882]	582	for( i; count ) {
[4998155]	583	__u32 idx = ring.submit_q.array[ (phead + i) & smask ];
[34b61882]	584	ring.submit_q.sqes[ idx ].user_data = 0;
	585	}
	586	return count;
	587	}
[47746a2]	588	#endif

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