From a9e3760b0838299649c0d57cca44daaf40ba3c33 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Sep 2026 22:12:34 -1000 Subject: sched_ext: Maintain an online cid mask in the scheduler arena Schedulers on the default cid mapping treat [0, nr_online_cids) as the online set and restart on hotplug. Schedulers that install their own mapping with scx_bpf_cid_override() have no way to learn which cids are online: the count no longer identifies members and the CPU-form cpumask is unusable from cid programs. This is an obvious hole in the cid API. Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's arena, allocated alongside the per-CPU scratch masks and populated after the cid mapping is finalized and before ops.init(), for child schedulers too. The pointer stays valid through ops.exit() with no reference to take. It is the arena offset as a void pointer, the same form struct_ops arena arguments arrive in. The verifier types the void return as a scalar for the program's arena cast. The mask follows the SCX hotplug notifications: seeded from cpu_active_mask and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask only inside a hotplug transition. Updates walk the scheduler list under the lock that also serializes unlinking. Reads are live, not atomic snapshots. Root initialization excludes hotplug. v2: Reworded the getter kerneldoc (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- tools/perf/util/expr.y | 391 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 391 insertions(+) create mode 100644 tools/perf/util/expr.y (limited to 'tools/perf/util/expr.y') diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y new file mode 100644 index 000000000..e20f64935 --- /dev/null +++ b/tools/perf/util/expr.y @@ -0,0 +1,391 @@ +/* Simple expression parser */ +%{ +#ifndef NDEBUG +#define YYDEBUG 1 +#endif +#include +#include +#include +#include "util/debug.h" +#define IN_EXPR_Y 1 +#include "expr.h" +#include "expr-bison.h" +int expr_lex(YYSTYPE * yylval_param , void *yyscanner); +%} + +%define api.pure full + +%parse-param { double *final_val } +%parse-param { struct expr_parse_ctx *ctx } +%parse-param { bool compute_ids } +%parse-param {void *scanner} +%lex-param {void* scanner} + +%union { + double num; + char *str; + struct ids { + /* + * When creating ids, holds the working set of event ids. NULL + * implies the set is empty. + */ + struct hashmap *ids; + /* + * The metric value. When not creating ids this is the value + * read from a counter, a constant or some computed value. When + * creating ids the value is either a constant or BOTTOM. NAN is + * used as the special BOTTOM value, representing a "set of all + * values" case. + */ + double val; + } ids; +} + +%token ID NUMBER MIN MAX IF ELSE LITERAL D_RATIO SOURCE_COUNT AGGR_NR HAS_EVENT STRCMP_CPUID_STR EXPR_ERROR +%left MIN MAX IF +%left '|' +%left '^' +%left '&' +%left '<' '>' +%left '-' '+' +%left '*' '/' '%' +%left NEG NOT +%type NUMBER LITERAL +%type ID +%destructor { free ($$); } +%type expr if_expr +%destructor { ids__free($$.ids); } + +%{ +static void expr_error(double *final_val __maybe_unused, + struct expr_parse_ctx *ctx __maybe_unused, + bool compute_ids __maybe_unused, + void *scanner __maybe_unused, + const char *s) +{ + pr_debug("%s\n", s); +} + +/* + * During compute ids, the special "bottom" value uses NAN to represent the set + * of all values. NAN is selected as it isn't a useful constant value. + */ +#define BOTTOM NAN + +/* During computing ids, does val represent a constant (non-BOTTOM) value? */ +static bool is_const(double val) +{ + return isfinite(val); +} + +static struct ids union_expr(struct ids ids1, struct ids ids2) +{ + struct ids result = { + .val = BOTTOM, + .ids = ids__union(ids1.ids, ids2.ids), + }; + return result; +} + +enum expr_id_kind { + EXPR_ID_KIND__VALUE, + EXPR_ID_KIND__SOURCE_COUNT, + EXPR_ID_KIND__AGGR_NR, +}; + +static struct ids handle_id(struct expr_parse_ctx *ctx, char *id, + bool compute_ids, enum expr_id_kind kind) +{ + struct ids result; + + if (!compute_ids) { + /* + * Compute the event's value from ID. If the ID isn't known then + * it isn't used to compute the formula so set to NAN. + */ + struct expr_id_data *data; + + result.val = NAN; + if (expr__resolve_id(ctx, id, &data) == 0) { + if (kind == EXPR_ID_KIND__SOURCE_COUNT) + result.val = expr_id_data__source_count(data); + else if (kind == EXPR_ID_KIND__AGGR_NR) + result.val = expr_id_data__aggr_nr(data); + else + result.val = expr_id_data__value(data); + } + result.ids = NULL; + free(id); + } else { + /* + * Set the value to BOTTOM to show that any value is possible + * when the event is computed. Create a set of just the ID. + */ + result.val = BOTTOM; + result.ids = ids__new(); + if (!result.ids || ids__insert(result.ids, id)) { + pr_err("Error creating IDs for '%s'", id); + free(id); + } + } + return result; +} + +/* + * If we're not computing ids or $1 and $3 are constants, compute the new + * constant value using OP. Its invariant that there are no ids. If computing + * ids for non-constants union the set of IDs that must be computed. + */ +#define BINARY_OP(RESULT, OP, LHS, RHS) \ + if (!compute_ids || (is_const(LHS.val) && is_const(RHS.val))) { \ + assert(LHS.ids == NULL); \ + assert(RHS.ids == NULL); \ + if (isnan(LHS.val) || isnan(RHS.val)) { \ + RESULT.val = NAN; \ + } else { \ + RESULT.val = LHS.val OP RHS.val; \ + } \ + RESULT.ids = NULL; \ + } else { \ + RESULT = union_expr(LHS, RHS); \ + } + +%} +%% + +start: if_expr +{ + if (compute_ids) + ctx->ids = ids__union($1.ids, ctx->ids); + + if (final_val) + *final_val = $1.val; +} +; + +if_expr: expr IF expr ELSE if_expr +{ + if (fpclassify($3.val) == FP_ZERO) { + /* + * The IF expression evaluated to 0 so treat as false, take the + * ELSE and discard everything else. + */ + $$.val = $5.val; + $$.ids = $5.ids; + ids__free($1.ids); + ids__free($3.ids); + } else if (!compute_ids || is_const($3.val)) { + /* + * If ids aren't computed then treat the expression as true. If + * ids are being computed and the IF expr is a non-zero + * constant, then also evaluate the true case. + */ + $$.val = $1.val; + $$.ids = $1.ids; + ids__free($3.ids); + ids__free($5.ids); + } else if ($1.val == $5.val) { + /* + * LHS == RHS, so both are an identical constant. No need to + * evaluate any events. + */ + $$.val = $1.val; + $$.ids = NULL; + ids__free($1.ids); + ids__free($3.ids); + ids__free($5.ids); + } else { + /* + * Value is either the LHS or RHS and we need the IF expression + * to compute it. + */ + $$ = union_expr($1, union_expr($3, $5)); + } +} +| expr +; + +expr: NUMBER +{ + $$.val = $1; + $$.ids = NULL; +} +| ID { $$ = handle_id(ctx, $1, compute_ids, EXPR_ID_KIND__VALUE); } +| SOURCE_COUNT '(' ID ')' { $$ = handle_id(ctx, $3, compute_ids, EXPR_ID_KIND__SOURCE_COUNT); } +| AGGR_NR '(' ID ')' { $$ = handle_id(ctx, $3, compute_ids, EXPR_ID_KIND__AGGR_NR); } +| HAS_EVENT '(' ID ')' +{ + $$.val = expr__has_event(ctx, compute_ids, $3); + $$.ids = NULL; + free($3); +} +| STRCMP_CPUID_STR '(' ID ')' +{ + $$.val = expr__strcmp_cpuid_str(ctx, compute_ids, $3); + $$.ids = NULL; + free($3); +} +| expr '|' expr +{ + if (is_const($1.val) && is_const($3.val)) { + assert($1.ids == NULL); + assert($3.ids == NULL); + $$.ids = NULL; + $$.val = (fpclassify($1.val) == FP_ZERO && fpclassify($3.val) == FP_ZERO) ? 0 : 1; + } else if (is_const($1.val)) { + assert($1.ids == NULL); + if (fpclassify($1.val) == FP_ZERO) { + $$ = $3; + } else { + $$.val = 1; + $$.ids = NULL; + ids__free($3.ids); + } + } else if (is_const($3.val)) { + assert($3.ids == NULL); + if (fpclassify($3.val) == FP_ZERO) { + $$ = $1; + } else { + $$.val = 1; + $$.ids = NULL; + ids__free($1.ids); + } + } else { + $$ = union_expr($1, $3); + } +} +| expr '&' expr +{ + if (is_const($1.val) && is_const($3.val)) { + assert($1.ids == NULL); + assert($3.ids == NULL); + $$.val = (fpclassify($1.val) != FP_ZERO && fpclassify($3.val) != FP_ZERO) ? 1 : 0; + $$.ids = NULL; + } else if (is_const($1.val)) { + assert($1.ids == NULL); + if (fpclassify($1.val) != FP_ZERO) { + $$ = $3; + } else { + $$.val = 0; + $$.ids = NULL; + ids__free($3.ids); + } + } else if (is_const($3.val)) { + assert($3.ids == NULL); + if (fpclassify($3.val) != FP_ZERO) { + $$ = $1; + } else { + $$.val = 0; + $$.ids = NULL; + ids__free($1.ids); + } + } else { + $$ = union_expr($1, $3); + } +} +| expr '^' expr +{ + if (is_const($1.val) && is_const($3.val)) { + assert($1.ids == NULL); + assert($3.ids == NULL); + $$.val = (fpclassify($1.val) == FP_ZERO) != (fpclassify($3.val) == FP_ZERO) ? 1 : 0; + $$.ids = NULL; + } else { + $$ = union_expr($1, $3); + } +} +| expr '<' expr { BINARY_OP($$, <, $1, $3); } +| expr '>' expr { BINARY_OP($$, >, $1, $3); } +| expr '+' expr { BINARY_OP($$, +, $1, $3); } +| expr '-' expr { BINARY_OP($$, -, $1, $3); } +| expr '*' expr { BINARY_OP($$, *, $1, $3); } +| expr '/' expr +{ + if (fpclassify($3.val) == FP_ZERO) { + pr_debug("division by zero\n"); + assert($3.ids == NULL); + if (compute_ids) + ids__free($1.ids); + $$.val = NAN; + $$.ids = NULL; + } else if (!compute_ids || (is_const($1.val) && is_const($3.val))) { + assert($1.ids == NULL); + assert($3.ids == NULL); + $$.val = $1.val / $3.val; + $$.ids = NULL; + } else { + /* LHS and/or RHS need computing from event IDs so union. */ + $$ = union_expr($1, $3); + } +} +| expr '%' expr +{ + if (fpclassify($3.val) == FP_ZERO) { + pr_debug("division by zero\n"); + YYABORT; + } else if (!compute_ids || (is_const($1.val) && is_const($3.val))) { + assert($1.ids == NULL); + assert($3.ids == NULL); + $$.val = (long)$1.val % (long)$3.val; + $$.ids = NULL; + } else { + /* LHS and/or RHS need computing from event IDs so union. */ + $$ = union_expr($1, $3); + } +} +| D_RATIO '(' expr ',' expr ')' +{ + if (fpclassify($5.val) == FP_ZERO) { + /* + * Division by constant zero always yields zero and no events + * are necessary. + */ + assert($5.ids == NULL); + $$.val = 0.0; + $$.ids = NULL; + ids__free($3.ids); + } else if (!compute_ids || (is_const($3.val) && is_const($5.val))) { + assert($3.ids == NULL); + assert($5.ids == NULL); + $$.val = $3.val / $5.val; + $$.ids = NULL; + } else { + /* LHS and/or RHS need computing from event IDs so union. */ + $$ = union_expr($3, $5); + } +} +| '-' expr %prec NEG +{ + $$.val = -$2.val; + $$.ids = $2.ids; +} +| '(' if_expr ')' +{ + $$ = $2; +} +| MIN '(' expr ',' expr ')' +{ + if (!compute_ids) { + $$.val = $3.val < $5.val ? $3.val : $5.val; + $$.ids = NULL; + } else { + $$ = union_expr($3, $5); + } +} +| MAX '(' expr ',' expr ')' +{ + if (!compute_ids) { + $$.val = $3.val > $5.val ? $3.val : $5.val; + $$.ids = NULL; + } else { + $$ = union_expr($3, $5); + } +} +| LITERAL +{ + $$.val = $1; + $$.ids = NULL; +} +; + +%% -- cgit v1.3.1