From 0bb47c89c36280339e560a15a3f66d64293b5304 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 24 Oct 2015 05:25:52 -0400 Subject: [PATCH] Cleanup callstack context Signed-off-by: Mathieu Desnoyers --- lttng-context-callstack.c | 73 ++++++++++++++++++++------------------- 1 file changed, 38 insertions(+), 35 deletions(-) diff --git a/lttng-context-callstack.c b/lttng-context-callstack.c index 57738bed..4dd984be 100644 --- a/lttng-context-callstack.c +++ b/lttng-context-callstack.c @@ -20,31 +20,32 @@ * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * - * The callstack context can be added to any kernel - * event. It records either the kernel or the userspace callstack, up to a - * max depth. The context is a CTF sequence, such that it uses only the space - * required for the number of callstack entries. + * The callstack context can be added to any kernel event. It records + * either the kernel or the userspace callstack, up to a max depth. The + * context is a CTF sequence, such that it uses only the space required + * for the number of callstack entries. * - * It allocates callstack buffers per-CPU up to 4 interrupt nesting. This - * nesting limit is the same as defined in the ring buffer. It therefore uses a - * fixed amount of memory, proportional to the number of CPUs: + * It allocates callstack buffers per-CPU up to 4 interrupt nesting. + * This nesting limit is the same as defined in the ring buffer. It + * therefore uses a fixed amount of memory, proportional to the number + * of CPUs: * * size = cpus * nest * depth * sizeof(unsigned long) * - * Which is about 800 bytes per-CPUs on 64-bit host and a depth of 25. The - * allocation is done at the initialization to avoid memory allocation - * overhead while tracing, using a shallow stack. + * Which is about 800 bytes per CPU on 64-bit host and a depth of 25. + * The allocation is done at the initialization to avoid memory + * allocation overhead while tracing, using a shallow stack. * * The kernel callstack is recovered using save_stack_trace(), and the * userspace callstack uses save_stack_trace_user(). They rely on frame - * pointers. These are usually available for the kernel, but the compiler - * option -fomit-frame-pointer frequently used in popular Linux distributions - * may cause the userspace callstack to be unreliable, and is a known - * limitation of this approach. If frame pointers are not available, it - * produces no error, but the callstack will be empty. We still provide the - * feature, because it works well for runtime environments having frame - * pointers. In the future, unwind support and/or last branch record may - * provide a solution to this problem. + * pointers. These are usually available for the kernel, but the + * compiler option -fomit-frame-pointer frequently used in popular Linux + * distributions may cause the userspace callstack to be unreliable, and + * is a known limitation of this approach. If frame pointers are not + * available, it produces no error, but the callstack will be empty. We + * still provide the feature, because it works well for runtime + * environments having frame pointers. In the future, unwind support + * and/or last branch record may provide a solution to this problem. * * The symbol name resolution is left to the trace reader. */ @@ -63,18 +64,24 @@ #define MAX_ENTRIES 25 -struct lttng_cs_nesting { +enum lttng_cs_ctx_modes { + CALLSTACK_KERNEL = 0, + CALLSTACK_USER = 1, + NR_CALLSTACK_MODES, +}; + +struct lttng_cs_dispatch { struct stack_trace stack_trace; unsigned long entries[MAX_ENTRIES]; }; struct lttng_cs { - struct lttng_cs_nesting level[RING_BUFFER_MAX_NESTING]; + struct lttng_cs_dispatch dispatch[RING_BUFFER_MAX_NESTING]; }; struct field_data { struct lttng_cs __percpu *cs_percpu; - int mode; + enum lttng_cs_ctx_modes mode; }; struct lttng_cs_type { @@ -83,11 +90,6 @@ struct lttng_cs_type { void (*save_func)(struct stack_trace *trace); }; -enum lttng_cs_ctx_modes { - CALLSTACK_KERNEL = 0, - CALLSTACK_USER = 1, -}; - static struct lttng_cs_type cs_types[] = { { .name = "callstack_kernel", @@ -102,7 +104,7 @@ static struct lttng_cs_type cs_types[] = { }; static -int init_type(int mode) +int init_type(enum lttng_cs_ctx_modes mode) { unsigned long func; @@ -138,7 +140,7 @@ struct stack_trace *stack_trace_context(struct lttng_ctx_field *field, if (nesting >= RING_BUFFER_MAX_NESTING) { return NULL; } - return &cs->level[nesting].stack_trace; + return &cs->dispatch[nesting].stack_trace; } /* @@ -228,7 +230,7 @@ void field_data_free(struct field_data *fdata) } static -struct field_data __percpu *field_data_create(int type) +struct field_data __percpu *field_data_create(enum lttng_cs_ctx_modes mode) { int cpu, i; struct lttng_cs __percpu *cs_set; @@ -247,14 +249,14 @@ struct field_data __percpu *field_data_create(int type) cs = per_cpu_ptr(cs_set, cpu); for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) { - struct lttng_cs_nesting *level; + struct lttng_cs_dispatch *dispatch; - level = &cs->level[i]; - level->stack_trace.entries = level->entries; - level->stack_trace.max_entries = MAX_ENTRIES; + dispatch = &cs->dispatch[i]; + dispatch->stack_trace.entries = dispatch->entries; + dispatch->stack_trace.max_entries = MAX_ENTRIES; } } - fdata->mode = type; + fdata->mode = mode; return fdata; error_alloc: @@ -271,7 +273,8 @@ void lttng_callstack_destroy(struct lttng_ctx_field *field) } static -int __lttng_add_callstack_generic(struct lttng_ctx **ctx, int mode) +int __lttng_add_callstack_generic(struct lttng_ctx **ctx, + enum lttng_cs_ctx_modes mode) { const char *ctx_name = cs_types[mode].name; struct lttng_ctx_field *field; -- 2.34.1