X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-context-procname.c;h=96a1b2ca2c36083b9d921220f1173f551256025d;hb=6ba6fd60507f8e045bdc4f1be14e9d99c6a15f7f;hp=b9bae82eba91be79fdd2ca1749fe2e5f2066b570;hpb=4c1ee94e5ef9ac3efb4a036108a9ff4eb24c238c;p=lttng-ust.git diff --git a/liblttng-ust/lttng-context-procname.c b/liblttng-ust/lttng-context-procname.c index b9bae82e..96a1b2ca 100644 --- a/liblttng-ust/lttng-context-procname.c +++ b/liblttng-ust/lttng-context-procname.c @@ -1,88 +1,125 @@ /* - * (C) Copyright 2009-2011 - - * Mathieu Desnoyers + * SPDX-License-Identifier: LGPL-2.1-only * - * LTTng UST procname context. + * Copyright (C) 2009-2012 Mathieu Desnoyers * - * Dual LGPL v2.1/GPL v2 license. + * LTTng UST procname context. */ -#include +#define _LGPL_SOURCE +#include #include #include -#include +#include +#include #include +#include "compat.h" +#include "lttng-tracer-core.h" + +#include "context-internal.h" -#define PROCNAME_LEN 17 /* includes \0 */ +/* Maximum number of nesting levels for the procname cache. */ +#define PROCNAME_NESTING_MAX 2 /* * We cache the result to ensure we don't trigger a system call for * each event. * Upon exec, procname changes, but exec takes care of throwing away * this cached version. + * The procname can also change by calling prctl(). The procname should + * be set for a thread before the first event is logged within this + * thread. */ -static char cached_procname[17]; +typedef char procname_array[PROCNAME_NESTING_MAX][17]; + +static DEFINE_URCU_TLS(procname_array, cached_procname); + +static DEFINE_URCU_TLS(int, procname_nesting); static inline -char *wrapper_getprocname(void) +const char *wrapper_getprocname(void) { - int ret; + int nesting = CMM_LOAD_SHARED(URCU_TLS(procname_nesting)); - if (caa_unlikely(!cached_procname[0])) { - ret = prctl(PR_GET_NAME, (unsigned long) cached_procname, - 0, 0, 0); - assert(!ret); + if (caa_unlikely(nesting >= PROCNAME_NESTING_MAX)) + return ""; + if (caa_unlikely(!URCU_TLS(cached_procname)[nesting][0])) { + CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting + 1); + /* Increment nesting before updating cache. */ + cmm_barrier(); + lttng_pthread_getname_np(URCU_TLS(cached_procname)[nesting], LTTNG_UST_ABI_PROCNAME_LEN); + URCU_TLS(cached_procname)[nesting][LTTNG_UST_ABI_PROCNAME_LEN - 1] = '\0'; + /* Decrement nesting after updating cache. */ + cmm_barrier(); + CMM_STORE_SHARED(URCU_TLS(procname_nesting), nesting); } - return cached_procname; + return URCU_TLS(cached_procname)[nesting]; } -void lttng_context_procname_reset(void) +/* Reset should not be called from a signal handler. */ +void lttng_ust_context_procname_reset(void) { - cached_procname[0] = '\0'; + CMM_STORE_SHARED(URCU_TLS(cached_procname)[1][0], '\0'); + CMM_STORE_SHARED(URCU_TLS(procname_nesting), 1); + CMM_STORE_SHARED(URCU_TLS(cached_procname)[0][0], '\0'); + CMM_STORE_SHARED(URCU_TLS(procname_nesting), 0); } static -size_t procname_get_size(size_t offset) +size_t procname_get_size(void *priv __attribute__((unused)), + size_t offset __attribute__((unused))) { - size_t size = 0; - - size += PROCNAME_LEN; - return size; + return LTTNG_UST_ABI_PROCNAME_LEN; } static -void procname_record(struct lttng_ctx_field *field, +void procname_record(void *priv __attribute__((unused)), struct lttng_ust_lib_ring_buffer_ctx *ctx, - struct ltt_channel *chan) + struct lttng_ust_channel_buffer *chan) { - char *procname; + const char *procname; procname = wrapper_getprocname(); - chan->ops->event_write(ctx, procname, PROCNAME_LEN); + chan->ops->event_write(ctx, procname, LTTNG_UST_ABI_PROCNAME_LEN, 1); +} + +static +void procname_get_value(void *priv __attribute__((unused)), + struct lttng_ust_ctx_value *value) +{ + value->u.str = wrapper_getprocname(); } -int lttng_add_procname_to_ctx(struct lttng_ctx **ctx) +static const struct lttng_ust_ctx_field *ctx_field = lttng_ust_static_ctx_field( + lttng_ust_static_event_field("procname", + lttng_ust_static_type_array_text(LTTNG_UST_ABI_PROCNAME_LEN), + false, false), + procname_get_size, + procname_record, + procname_get_value, + NULL, NULL); + +int lttng_add_procname_to_ctx(struct lttng_ust_ctx **ctx) { - struct lttng_ctx_field *field; - - field = lttng_append_context(ctx); - if (!field) - return -ENOMEM; - if (lttng_find_context(*ctx, "procname")) { - lttng_remove_context_field(ctx, field); - return -EEXIST; + int ret; + + if (lttng_find_context(*ctx, ctx_field->event_field->name)) { + ret = -EEXIST; + goto error_find_context; } - field->event_field.name = "procname"; - field->event_field.type.atype = atype_array; - field->event_field.type.u.array.elem_type.atype = atype_integer; - field->event_field.type.u.array.elem_type.u.basic.integer.size = sizeof(char) * CHAR_BIT; - field->event_field.type.u.array.elem_type.u.basic.integer.alignment = lttng_alignof(char) * CHAR_BIT; - field->event_field.type.u.array.elem_type.u.basic.integer.signedness = lttng_is_signed_type(char); - field->event_field.type.u.array.elem_type.u.basic.integer.reverse_byte_order = 0; - field->event_field.type.u.array.elem_type.u.basic.integer.base = 10; - field->event_field.type.u.array.elem_type.u.basic.integer.encoding = lttng_encode_UTF8; - field->event_field.type.u.array.length = PROCNAME_LEN; - field->get_size = procname_get_size; - field->record = procname_record; + ret = lttng_ust_context_append(ctx, ctx_field); + if (ret) + return ret; return 0; + +error_find_context: + return ret; +} + +/* + * Force a read (imply TLS fixup for dlopen) of TLS variables. + */ +void lttng_fixup_procname_tls(void) +{ + asm volatile ("" : : "m" (URCU_TLS(cached_procname)[0])); }