From 79dfbf429c229ef733c5d8691a681edb91bee871 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 26 Jan 2012 15:12:51 -0500 Subject: [PATCH] Properly fix the timekeeping overflow detection MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The underlying issue was a mismatch between the ring buffer configuration description of the number of clock bits (32) saved and the actual number used (27). Introduce LTTNG_COMPACT_EVENT_BITS and LTTNG_COMPACT_TSC_BITS across the code to remove all hardcoded instances of these values to ensure this kind of mistake does not happen again. Signed-off-by: Mathieu Desnoyers Reported-by: Sébastien Barthélémy --- liblttng-ust/ltt-ring-buffer-client.h | 34 ++++++++++++++++++++------- 1 file changed, 26 insertions(+), 8 deletions(-) diff --git a/liblttng-ust/ltt-ring-buffer-client.h b/liblttng-ust/ltt-ring-buffer-client.h index a2ace400..ce9d263c 100644 --- a/liblttng-ust/ltt-ring-buffer-client.h +++ b/liblttng-ust/ltt-ring-buffer-client.h @@ -15,6 +15,9 @@ #include "ltt-tracer.h" #include "../libringbuffer/frontend_types.h" +#define LTTNG_COMPACT_EVENT_BITS 5 +#define LTTNG_COMPACT_TSC_BITS 27 + /* * Keep the natural field alignment for _each field_ within this structure if * you ever add/remove a field from this header. Packed attribute is not used @@ -110,8 +113,8 @@ unsigned char record_header_size(const struct lttng_ust_lib_ring_buffer_config * if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTT_RFLAG_EXTENDED))) { offset += sizeof(uint32_t); /* id and timestamp */ } else { - /* Minimum space taken by 5-bit id */ - offset += sizeof(uint8_t); + /* Minimum space taken by LTTNG_COMPACT_EVENT_BITS id */ + offset += (LTTNG_COMPACT_EVENT_BITS + CHAR_BIT - 1) / CHAR_BIT; /* Align extended struct on largest member */ offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t)); offset += sizeof(uint32_t); /* id */ @@ -177,8 +180,14 @@ void ltt_write_event_header(const struct lttng_ust_lib_ring_buffer_config *confi { uint32_t id_time = 0; - bt_bitfield_write(&id_time, uint32_t, 0, 5, event_id); - bt_bitfield_write(&id_time, uint32_t, 5, 27, ctx->tsc); + bt_bitfield_write(&id_time, uint32_t, + 0, + LTTNG_COMPACT_EVENT_BITS, + event_id); + bt_bitfield_write(&id_time, uint32_t, + LTTNG_COMPACT_EVENT_BITS, + LTTNG_COMPACT_TSC_BITS, + ctx->tsc); lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time)); break; } @@ -219,14 +228,23 @@ void ltt_write_event_header_slow(const struct lttng_ust_lib_ring_buffer_config * if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTT_RFLAG_EXTENDED))) { uint32_t id_time = 0; - bt_bitfield_write(&id_time, uint32_t, 0, 5, event_id); - bt_bitfield_write(&id_time, uint32_t, 5, 27, ctx->tsc); + bt_bitfield_write(&id_time, uint32_t, + 0, + LTTNG_COMPACT_EVENT_BITS, + event_id); + bt_bitfield_write(&id_time, uint32_t, + LTTNG_COMPACT_EVENT_BITS, + LTTNG_COMPACT_TSC_BITS, + ctx->tsc); lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time)); } else { uint8_t id = 0; uint64_t timestamp = ctx->tsc; - bt_bitfield_write(&id, uint8_t, 0, 5, 31); + bt_bitfield_write(&id, uint8_t, + 0, + LTTNG_COMPACT_EVENT_BITS, + 31); lib_ring_buffer_write(config, ctx, &id, sizeof(id)); /* Align extended struct on largest member */ lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t)); @@ -365,7 +383,7 @@ static const struct lttng_ust_lib_ring_buffer_config client_config = { .cb.buffer_create = client_buffer_create, .cb.buffer_finalize = client_buffer_finalize, - .tsc_bits = 32, + .tsc_bits = LTTNG_COMPACT_TSC_BITS, .alloc = RING_BUFFER_ALLOC_PER_CPU, .sync = RING_BUFFER_SYNC_GLOBAL, .mode = RING_BUFFER_MODE_TEMPLATE, -- 2.34.1