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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] Tracing cleanups and simplify tb_set_size(). Dynamic
# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID d8a39152f982f97ba6c1267e58f81dad366ed05b
# Parent a663683fe8cb2eaea33f18d55bb8b0ee93867d9b
Tracing cleanups and simplify tb_set_size(). Dynamic
buffer shrinking is unsafe without heavier weight SMP
synchronisation.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
diff -r a663683fe8cb -r d8a39152f982 xen/common/trace.c
--- a/xen/common/trace.c Sun Oct 30 21:35:06 2005
+++ b/xen/common/trace.c Sun Oct 30 22:17:58 2005
@@ -36,53 +36,29 @@
integer_param("tbuf_size", opt_tbuf_size);
/* Pointers to the meta-data objects for all system trace buffers */
-struct t_buf *t_bufs[NR_CPUS];
+static struct t_buf *t_bufs[NR_CPUS];
/* a flag recording whether initialization has been done */
/* or more properly, if the tbuf subsystem is enabled right now */
int tb_init_done = 0;
/* which CPUs tracing is enabled on */
-unsigned long tb_cpu_mask = (~0UL);
+static unsigned long tb_cpu_mask = (~0UL);
/* which tracing events are enabled */
-u32 tb_event_mask = TRC_ALL;
-
-/**
- * init_trace_bufs - performs initialization of the per-cpu trace buffers.
+static u32 tb_event_mask = TRC_ALL;
+
+/**
+ * alloc_trace_bufs - performs initialization of the per-cpu trace buffers.
*
* This function is called at start of day in order to initialize the per-cpu
* trace buffers. The trace buffers are then available for debugging use, via
* the %TRACE_xD macros exported in <xen/trace.h>.
- */
-void init_trace_bufs(void)
-{
- extern int alloc_trace_bufs(void);
-
- if ( opt_tbuf_size == 0 )
- {
- printk("Xen trace buffers: disabled\n");
- return;
- }
-
- if (alloc_trace_bufs() == 0) {
- printk("Xen trace buffers: initialised\n");
- wmb(); /* above must be visible before tb_init_done flag set */
- tb_init_done = 1;
- }
-}
-
-/**
- * alloc_trace_bufs - performs initialization of the per-cpu trace buffers.
- *
- * This function is called at start of day in order to initialize the per-cpu
- * trace buffers. The trace buffers are then available for debugging use, via
- * the %TRACE_xD macros exported in <xen/trace.h>.
*
* This function may also be called later when enabling trace buffers
* via the SET_SIZE hypercall.
*/
-int alloc_trace_bufs(void)
+static int alloc_trace_bufs(void)
{
int i, order;
unsigned long nr_pages;
@@ -125,37 +101,52 @@
*
* This function is called when the SET_SIZE hypercall is done.
*/
-int tb_set_size(int size)
-{
- // There are three cases to handle:
- // 1. Changing from 0 to non-zero ==> simple allocate
- // 2. Changing from non-zero to 0 ==> simple deallocate
- // 3. Changing size ==> deallocate and reallocate? Or disallow?
- // User can just do a change to 0, then a change to the new size.
- //
- // Tracing must be disabled (tb_init_done==0) before calling this
-
- if (opt_tbuf_size == 0 && size > 0) {
- // What if size is too big? alloc_xenheap will complain.
- opt_tbuf_size = size;
- if (alloc_trace_bufs() != 0)
- return -EINVAL;
- wmb();
- printk("Xen trace buffers: initialized\n");
- return 0;
- }
- else if (opt_tbuf_size > 0 && size == 0) {
- int order = get_order_from_pages(num_online_cpus() * opt_tbuf_size);
- // is there a way to undo SHARE_PFN_WITH_DOMAIN?
- free_xenheap_pages(t_bufs[0], order);
+static int tb_set_size(int size)
+{
+ /*
+ * Setting size is a one-shot operation. It can be done either at
+ * boot time or via control tools, but not by both. Once buffers
+ * are created they cannot be destroyed.
+ */
+ if ( (opt_tbuf_size != 0) || (size <= 0) )
+ {
+ DPRINTK("tb_set_size from %d to %d not implemented\n",
+ opt_tbuf_size, size);
+ return -EINVAL;
+ }
+
+ opt_tbuf_size = size;
+ if ( alloc_trace_bufs() != 0 )
+ {
opt_tbuf_size = 0;
- printk("Xen trace buffers: uninitialized\n");
- return 0;
- }
- else {
- printk("tb_set_size from %d to %d not implemented\n", opt_tbuf_size,
size);
- printk("change size from %d to 0, and then to %d\n", opt_tbuf_size,
size);
- return -EINVAL;
+ return -EINVAL;
+ }
+
+ printk("Xen trace buffers: initialized\n");
+ return 0;
+}
+
+
+/**
+ * init_trace_bufs - performs initialization of the per-cpu trace buffers.
+ *
+ * This function is called at start of day in order to initialize the per-cpu
+ * trace buffers. The trace buffers are then available for debugging use, via
+ * the %TRACE_xD macros exported in <xen/trace.h>.
+ */
+void init_trace_bufs(void)
+{
+ if ( opt_tbuf_size == 0 )
+ {
+ printk("Xen trace buffers: disabled\n");
+ return;
+ }
+
+ if ( alloc_trace_bufs() == 0 )
+ {
+ printk("Xen trace buffers: initialised\n");
+ wmb(); /* above must be visible before tb_init_done flag set */
+ tb_init_done = 1;
}
}
@@ -169,14 +160,17 @@
static spinlock_t lock = SPIN_LOCK_UNLOCKED;
int rc = 0;
- // Commenting this out since we have to allow some of these operations
- // in order to enable dynamic control of the trace buffers.
- // if ( !tb_init_done )
- // return -EINVAL;
-
spin_lock(&lock);
- switch ( tbc->op)
+ if ( !tb_init_done &&
+ (tbc->op != DOM0_TBUF_SET_SIZE) &&
+ (tbc->op != DOM0_TBUF_ENABLE) )
+ {
+ spin_unlock(&lock);
+ return -EINVAL;
+ }
+
+ switch ( tbc->op )
{
case DOM0_TBUF_GET_INFO:
tbc->cpu_mask = tb_cpu_mask;
@@ -191,36 +185,88 @@
tb_event_mask = tbc->evt_mask;
break;
case DOM0_TBUF_SET_SIZE:
- // Change trace buffer allocation.
- // Trace buffers must be disabled to do this.
- if (tb_init_done) {
- printk("attempt to change size with tbufs enabled\n");
- rc = -EINVAL;
- }
- else
- rc = tb_set_size(tbc->size);
+ rc = !tb_init_done ? tb_set_size(tbc->size) : -EINVAL;
break;
case DOM0_TBUF_ENABLE:
- // Enable trace buffers. Size must be non-zero, ie, buffers
- // must already be allocated.
- if (opt_tbuf_size == 0)
+ /* Enable trace buffers. Check buffers are already allocated. */
+ if ( opt_tbuf_size == 0 )
rc = -EINVAL;
else
tb_init_done = 1;
break;
case DOM0_TBUF_DISABLE:
- // Disable trace buffers. Just stops new records from being written,
- // does not deallocate any memory.
+ /*
+ * Disable trace buffers. Just stops new records from being written,
+ * does not deallocate any memory.
+ */
tb_init_done = 0;
- printk("Xen trace buffers: disabled\n");
break;
default:
rc = -EINVAL;
+ break;
}
spin_unlock(&lock);
return rc;
+}
+
+/**
+ * trace - Enters a trace tuple into the trace buffer for the current CPU.
+ * @event: the event type being logged
+ * @d1...d5: the data items for the event being logged
+ *
+ * Logs a trace record into the appropriate buffer. Returns nonzero on
+ * failure, otherwise 0. Failure occurs only if the trace buffers are not yet
+ * initialised.
+ */
+void trace(u32 event, unsigned long d1, unsigned long d2,
+ unsigned long d3, unsigned long d4, unsigned long d5)
+{
+ atomic_t old, new, seen;
+ struct t_buf *buf;
+ struct t_rec *rec;
+
+ BUG_ON(!tb_init_done);
+
+ if ( (tb_event_mask & event) == 0 )
+ return;
+
+ /* match class */
+ if ( ((tb_event_mask >> TRC_CLS_SHIFT) & (event >> TRC_CLS_SHIFT)) == 0 )
+ return;
+
+ /* then match subclass */
+ if ( (((tb_event_mask >> TRC_SUBCLS_SHIFT) & 0xf )
+ & ((event >> TRC_SUBCLS_SHIFT) & 0xf )) == 0 )
+ return;
+
+ if ( (tb_cpu_mask & (1UL << smp_processor_id())) == 0 )
+ return;
+
+ /* Read tb_init_done /before/ t_bufs. */
+ rmb();
+
+ buf = t_bufs[smp_processor_id()];
+
+ do
+ {
+ old = buf->rec_idx;
+ _atomic_set(new, (_atomic_read(old) + 1) % buf->rec_num);
+ seen = atomic_compareandswap(old, new, &buf->rec_idx);
+ }
+ while ( unlikely(_atomic_read(seen) != _atomic_read(old)) );
+
+ wmb();
+
+ rec = &buf->rec[_atomic_read(old)];
+ rdtscll(rec->cycles);
+ rec->event = event;
+ rec->data[0] = d1;
+ rec->data[1] = d2;
+ rec->data[2] = d3;
+ rec->data[3] = d4;
+ rec->data[4] = d5;
}
/*
diff -r a663683fe8cb -r d8a39152f982 xen/include/xen/trace.h
--- a/xen/include/xen/trace.h Sun Oct 30 21:35:06 2005
+++ b/xen/include/xen/trace.h Sun Oct 30 22:17:58 2005
@@ -32,10 +32,7 @@
#include <public/dom0_ops.h>
#include <public/trace.h>
-extern struct t_buf *t_bufs[];
extern int tb_init_done;
-extern unsigned long tb_cpu_mask;
-extern u32 tb_event_mask;
/* Used to initialise trace buffer functionality */
void init_trace_bufs(void);
@@ -43,72 +40,20 @@
/* used to retrieve the physical address of the trace buffers */
int tb_control(dom0_tbufcontrol_t *tbc);
-/**
- * trace - Enters a trace tuple into the trace buffer for the current CPU.
- * @event: the event type being logged
- * @d1...d5: the data items for the event being logged
- *
- * Logs a trace record into the appropriate buffer. Returns nonzero on
- * failure, otherwise 0. Failure occurs only if the trace buffers are not yet
- * initialised.
- */
-static inline int trace(u32 event, unsigned long d1, unsigned long d2,
- unsigned long d3, unsigned long d4, unsigned long d5)
-{
- atomic_t old, new, seen;
- struct t_buf *buf;
- struct t_rec *rec;
-
- if ( !tb_init_done )
- return -1;
-
- if ( (tb_event_mask & event) == 0 )
- return 0;
-
- /* match class */
- if ( ((tb_event_mask >> TRC_CLS_SHIFT) & (event >> TRC_CLS_SHIFT)) == 0 )
- return 0;
-
- /* then match subclass */
- if ( (((tb_event_mask >> TRC_SUBCLS_SHIFT) & 0xf )
- & ((event >> TRC_SUBCLS_SHIFT) & 0xf )) == 0 )
- return 0;
-
- if ( (tb_cpu_mask & (1UL << smp_processor_id())) == 0 )
- return 0;
-
- buf = t_bufs[smp_processor_id()];
-
- do
- {
- old = buf->rec_idx;
- _atomic_set(new, (_atomic_read(old) + 1) % buf->rec_num);
- seen = atomic_compareandswap(old, new, &buf->rec_idx);
- }
- while ( unlikely(_atomic_read(seen) != _atomic_read(old)) );
-
- wmb();
-
- rec = &buf->rec[_atomic_read(old)];
- rdtscll(rec->cycles);
- rec->event = event;
- rec->data[0] = d1;
- rec->data[1] = d2;
- rec->data[2] = d3;
- rec->data[3] = d4;
- rec->data[4] = d5;
-
- return 0;
-}
+void trace(u32 event, unsigned long d1, unsigned long d2,
+ unsigned long d3, unsigned long d4, unsigned long d5);
/* Avoids troubling the caller with casting their arguments to a trace macro */
-#define trace_do_casts(e,d1,d2,d3,d4,d5) \
- trace(e, \
- (unsigned long)d1, \
- (unsigned long)d2, \
- (unsigned long)d3, \
- (unsigned long)d4, \
- (unsigned long)d5)
+#define trace_do_casts(e,d1,d2,d3,d4,d5) \
+ do { \
+ if ( tb_init_done ) \
+ trace(e, \
+ (unsigned long)d1, \
+ (unsigned long)d2, \
+ (unsigned long)d3, \
+ (unsigned long)d4, \
+ (unsigned long)d5); \
+ } while ( 0 )
/* Convenience macros for calling the trace function. */
#define TRACE_0D(event) trace_do_casts(event,0, 0, 0, 0, 0 )
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