Commit e2ace001 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Steven Rostedt

tracing: Choose static tp_printk buffer by explicit nesting count

Currently, the trace_printk code chooses which static buffer to use based
on what type of atomic context (NMI, IRQ, etc) it's in.  Simplify the
code and make it more robust: simply count the nesting depth and choose
a buffer based on the current nesting depth.

The new code will only drop an event if we nest more than 4 deep,
and the old code was guaranteed to malfunction if that happened.

Link: http://lkml.kernel.org/r/07ab03aecfba25fcce8f9a211b14c9c5e2865c58.1464289095.git.luto@kernel.orgAcked-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 35abb67d
...@@ -2339,83 +2339,41 @@ static void __trace_userstack(struct trace_array *tr, unsigned long flags) ...@@ -2339,83 +2339,41 @@ static void __trace_userstack(struct trace_array *tr, unsigned long flags)
/* created for use with alloc_percpu */ /* created for use with alloc_percpu */
struct trace_buffer_struct { struct trace_buffer_struct {
char buffer[TRACE_BUF_SIZE]; int nesting;
char buffer[4][TRACE_BUF_SIZE];
}; };
static struct trace_buffer_struct *trace_percpu_buffer; static struct trace_buffer_struct *trace_percpu_buffer;
static struct trace_buffer_struct *trace_percpu_sirq_buffer;
static struct trace_buffer_struct *trace_percpu_irq_buffer;
static struct trace_buffer_struct *trace_percpu_nmi_buffer;
/* /*
* The buffer used is dependent on the context. There is a per cpu * Thise allows for lockless recording. If we're nested too deeply, then
* buffer for normal context, softirq contex, hard irq context and * this returns NULL.
* for NMI context. Thise allows for lockless recording.
*
* Note, if the buffers failed to be allocated, then this returns NULL
*/ */
static char *get_trace_buf(void) static char *get_trace_buf(void)
{ {
struct trace_buffer_struct *percpu_buffer; struct trace_buffer_struct *buffer = this_cpu_ptr(trace_percpu_buffer);
/*
* If we have allocated per cpu buffers, then we do not
* need to do any locking.
*/
if (in_nmi())
percpu_buffer = trace_percpu_nmi_buffer;
else if (in_irq())
percpu_buffer = trace_percpu_irq_buffer;
else if (in_softirq())
percpu_buffer = trace_percpu_sirq_buffer;
else
percpu_buffer = trace_percpu_buffer;
if (!percpu_buffer) if (!buffer || buffer->nesting >= 4)
return NULL; return NULL;
return this_cpu_ptr(&percpu_buffer->buffer[0]); return &buffer->buffer[buffer->nesting++][0];
}
static void put_trace_buf(void)
{
this_cpu_dec(trace_percpu_buffer->nesting);
} }
static int alloc_percpu_trace_buffer(void) static int alloc_percpu_trace_buffer(void)
{ {
struct trace_buffer_struct *buffers; struct trace_buffer_struct *buffers;
struct trace_buffer_struct *sirq_buffers;
struct trace_buffer_struct *irq_buffers;
struct trace_buffer_struct *nmi_buffers;
buffers = alloc_percpu(struct trace_buffer_struct); buffers = alloc_percpu(struct trace_buffer_struct);
if (!buffers) if (WARN(!buffers, "Could not allocate percpu trace_printk buffer"))
goto err_warn; return -ENOMEM;
sirq_buffers = alloc_percpu(struct trace_buffer_struct);
if (!sirq_buffers)
goto err_sirq;
irq_buffers = alloc_percpu(struct trace_buffer_struct);
if (!irq_buffers)
goto err_irq;
nmi_buffers = alloc_percpu(struct trace_buffer_struct);
if (!nmi_buffers)
goto err_nmi;
trace_percpu_buffer = buffers; trace_percpu_buffer = buffers;
trace_percpu_sirq_buffer = sirq_buffers;
trace_percpu_irq_buffer = irq_buffers;
trace_percpu_nmi_buffer = nmi_buffers;
return 0; return 0;
err_nmi:
free_percpu(irq_buffers);
err_irq:
free_percpu(sirq_buffers);
err_sirq:
free_percpu(buffers);
err_warn:
WARN(1, "Could not allocate percpu trace_printk buffer");
return -ENOMEM;
} }
static int buffers_allocated; static int buffers_allocated;
...@@ -2506,7 +2464,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) ...@@ -2506,7 +2464,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
tbuffer = get_trace_buf(); tbuffer = get_trace_buf();
if (!tbuffer) { if (!tbuffer) {
len = 0; len = 0;
goto out; goto out_nobuffer;
} }
len = vbin_printf((u32 *)tbuffer, TRACE_BUF_SIZE/sizeof(int), fmt, args); len = vbin_printf((u32 *)tbuffer, TRACE_BUF_SIZE/sizeof(int), fmt, args);
...@@ -2532,6 +2490,9 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args) ...@@ -2532,6 +2490,9 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
} }
out: out:
put_trace_buf();
out_nobuffer:
preempt_enable_notrace(); preempt_enable_notrace();
unpause_graph_tracing(); unpause_graph_tracing();
...@@ -2563,7 +2524,7 @@ __trace_array_vprintk(struct ring_buffer *buffer, ...@@ -2563,7 +2524,7 @@ __trace_array_vprintk(struct ring_buffer *buffer,
tbuffer = get_trace_buf(); tbuffer = get_trace_buf();
if (!tbuffer) { if (!tbuffer) {
len = 0; len = 0;
goto out; goto out_nobuffer;
} }
len = vscnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args); len = vscnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args);
...@@ -2582,7 +2543,11 @@ __trace_array_vprintk(struct ring_buffer *buffer, ...@@ -2582,7 +2543,11 @@ __trace_array_vprintk(struct ring_buffer *buffer,
__buffer_unlock_commit(buffer, event); __buffer_unlock_commit(buffer, event);
ftrace_trace_stack(&global_trace, buffer, flags, 6, pc, NULL); ftrace_trace_stack(&global_trace, buffer, flags, 6, pc, NULL);
} }
out:
out:
put_trace_buf();
out_nobuffer:
preempt_enable_notrace(); preempt_enable_notrace();
unpause_graph_tracing(); unpause_graph_tracing();
......
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