From ecfad924e044a187d0ac9fc4561b45b285e7f8c5 Mon Sep 17 00:00:00 2001
From: Ingo Weinhold <ingo_weinhold@gmx.de>
Date: Sat, 20 Sep 2008 22:04:03 +0000
Subject: [PATCH] Solution for the potential deadlock when needing to flush the
profiling buffer during a timer event that interrupted a kernel function: We
do now flush the buffer as soon as it is 70% full, *if* we didn't interrupt a
kernel function. When the buffer runs full and we still haven't hit a user
function, we drop the tick. The number of dropped ticks is recorded and sent
to the debugger with the next update message. Reverted the previous partial
solution (the temporary disabling of profiling while in debugger support
code).
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@27658 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
headers/os/kernel/debugger.h | 3 +
headers/private/kernel/user_debugger.h | 14 ++--
src/system/kernel/debug/user_debugger.cpp | 96 +++++++----------------
3 files changed, 40 insertions(+), 73 deletions(-)
diff --git a/headers/os/kernel/debugger.h b/headers/os/kernel/debugger.h
index 220f859868..c8be65120a 100644
--- a/headers/os/kernel/debugger.h
+++ b/headers/os/kernel/debugger.h
@@ -556,6 +556,9 @@ typedef struct {
int32 stack_depth; // number of return addresses per
// tick
int32 sample_count; // number of samples in the buffer
+ int32 dropped_ticks; // number of ticks that had been
+ // dropped, since the buffer was
+ // full
bool stopped; // if true, the thread is no longer
// being profiled
} debug_profiler_update;
diff --git a/headers/private/kernel/user_debugger.h b/headers/private/kernel/user_debugger.h
index 619c69db4b..e6f6bdedff 100644
--- a/headers/private/kernel/user_debugger.h
+++ b/headers/private/kernel/user_debugger.h
@@ -15,9 +15,10 @@
// limits
-#define B_DEBUG_MAX_PROFILE_FUNCTIONS 100000
-#define B_DEBUG_MIN_PROFILE_INTERVAL 100 /* in us */
-#define B_DEBUG_STACK_TRACE_DEPTH 5
+#define B_DEBUG_MAX_PROFILE_FUNCTIONS 100000
+#define B_DEBUG_MIN_PROFILE_INTERVAL 100 /* in us */
+#define B_DEBUG_STACK_TRACE_DEPTH 5
+#define B_DEBUG_PROFILE_BUFFER_FLUSH_THRESHOLD 70 /* in % */
struct function_profile_info;
@@ -84,15 +85,18 @@ struct thread_debug_info {
// sample buffer
int32 max_samples;
// maximum number of samples the buffer can hold
+ int32 flush_threshold;
+ // number of sample when the buffer is flushed (if possible)
int32 sample_count;
// number of samples the buffer currently holds
int32 stack_depth;
// number of return addresses to record per timer interval
+ int32 dropped_ticks;
+ // number of ticks that had to be dropped when the sample buffer was
+ // full and couldn't be flushed
int32 image_event;
// number of the image event when the first sample was written into
// the buffer
- int32 disabled;
- // if > 0, profiling is temporarily disabled for the thread
bool buffer_full;
// indicates that the sample buffer is full
union {
diff --git a/src/system/kernel/debug/user_debugger.cpp b/src/system/kernel/debug/user_debugger.cpp
index d150e1ffb8..c6505f036a 100644
--- a/src/system/kernel/debug/user_debugger.cpp
+++ b/src/system/kernel/debug/user_debugger.cpp
@@ -54,51 +54,6 @@ static status_t ensure_debugger_installed(team_id teamID, port_id *port = NULL);
static void get_team_debug_info(team_debug_info &teamDebugInfo);
-static void
-enable_profiling()
-{
- struct thread* thread = thread_get_current_thread();
-
- InterruptsSpinLocker _(gThreadSpinlock);
-
- if (--thread->debug_info.profile.disabled > 0)
- return;
-
- if (thread->debug_info.profile.samples != NULL
- && !thread->debug_info.profile.buffer_full) {
- // install profiling timer
- schedule_profiling_timer(thread,
- thread->debug_info.profile.interval_left);
- }
-}
-
-
-static void
-disable_profiling()
-{
- struct thread* thread = thread_get_current_thread();
-
- InterruptsSpinLocker _(gThreadSpinlock);
-
- if (thread->debug_info.profile.disabled++ > 0) {
- ASSERT(thread->debug_info.profile.installed_timer == NULL);
- return;
- }
-
- // if running, cancel the profiling timer
- struct timer* timer = thread->debug_info.profile.installed_timer;
- if (timer != NULL) {
- // track remaining time
- bigtime_t left = thread->debug_info.profile.timer_end - system_time();
- thread->debug_info.profile.interval_left = max_c(left, 0);
- thread->debug_info.profile.installed_timer = NULL;
-
- // cancel timer
- cancel_timer(timer);
- }
-}
-
-
static status_t
kill_interruptable_write_port(port_id port, int32 code, const void *buffer,
size_t bufferSize)
@@ -119,8 +74,6 @@ debugger_write(port_id port, int32 code, const void *buffer, size_t bufferSize,
status_t error = B_OK;
- disable_profiling();
-
// get the team debug info
team_debug_info teamDebugInfo;
get_team_debug_info(teamDebugInfo);
@@ -132,7 +85,6 @@ debugger_write(port_id port, int32 code, const void *buffer, size_t bufferSize,
dontWait ? (uint32)B_RELATIVE_TIMEOUT : (uint32)B_KILL_CAN_INTERRUPT, 0);
if (error != B_OK) {
TRACE(("debugger_write() done1: %lx\n", error));
- enable_profiling();
return error;
}
@@ -159,7 +111,6 @@ debugger_write(port_id port, int32 code, const void *buffer, size_t bufferSize,
TRACE(("debugger_write() done: %lx\n", error));
- enable_profiling();
return error;
}
@@ -337,7 +288,6 @@ init_thread_debug_info(struct thread_debug_info *info)
info->ignore_signals_once = 0;
info->profile.sample_area = -1;
info->profile.samples = NULL;
- info->profile.disabled = 0;
info->profile.buffer_full = false;
info->profile.installed_timer = NULL;
}
@@ -364,7 +314,6 @@ clear_thread_debug_info(struct thread_debug_info *info, bool dying)
info->ignore_signals_once = 0;
info->profile.sample_area = -1;
info->profile.samples = NULL;
- info->profile.disabled = 0;
info->profile.buffer_full = false;
}
}
@@ -735,8 +684,6 @@ static status_t
thread_hit_debug_event(debug_debugger_message event, const void *message,
int32 size, bool requireDebugger)
{
- disable_profiling();
-
status_t result;
bool restart;
do {
@@ -745,8 +692,6 @@ thread_hit_debug_event(debug_debugger_message event, const void *message,
requireDebugger, restart);
} while (result >= 0 && restart);
- enable_profiling();
-
return result;
}
@@ -1082,11 +1027,11 @@ user_debug_thread_exiting(struct thread* thread)
area_id sampleArea = threadDebugInfo.profile.sample_area;
int32 sampleCount = threadDebugInfo.profile.sample_count;
+ int32 droppedTicks = threadDebugInfo.profile.dropped_ticks;
int32 stackDepth = threadDebugInfo.profile.stack_depth;
int32 imageEvent = threadDebugInfo.profile.image_event;
threadDebugInfo.profile.sample_area = -1;
threadDebugInfo.profile.samples = NULL;
- threadDebugInfo.profile.disabled = 0;
threadDebugInfo.profile.buffer_full = false;
atomic_or(&threadDebugInfo.flags, B_THREAD_DEBUG_DYING);
@@ -1100,6 +1045,7 @@ user_debug_thread_exiting(struct thread* thread)
message.origin.team = thread->team->id;
message.origin.nub_port = -1; // asynchronous message
message.sample_count = sampleCount;
+ message.dropped_ticks = droppedTicks;
message.stack_depth = stackDepth;
message.image_event = imageEvent;
message.stopped = true;
@@ -1254,9 +1200,19 @@ profiling_do_sample(bool& flushBuffer)
int32 imageEvent = thread->team->debug_info.image_event;
if (debugInfo.profile.sample_count > 0) {
if (debugInfo.profile.image_event < imageEvent
- || debugInfo.profile.max_samples - sampleCount < stackDepth) {
- flushBuffer = true;
- return true;
+ || debugInfo.profile.flush_threshold - sampleCount < stackDepth) {
+ if (!IS_KERNEL_ADDRESS(arch_debug_get_interrupt_pc())) {
+ flushBuffer = true;
+ return true;
+ }
+
+ // We can't flush the buffer now, since we interrupted a kernel
+ // function. If the buffer is not full yet, we add the samples,
+ // otherwise we have to drop them.
+ if (debugInfo.profile.max_samples - sampleCount < stackDepth) {
+ debugInfo.profile.dropped_ticks++;
+ return true;
+ }
}
} else {
// first sample -- set the image event
@@ -1291,11 +1247,13 @@ profiling_buffer_full(void*)
if (debugInfo.profile.samples != NULL && debugInfo.profile.buffer_full) {
int32 sampleCount = debugInfo.profile.sample_count;
+ int32 droppedTicks = debugInfo.profile.dropped_ticks;
int32 stackDepth = debugInfo.profile.stack_depth;
int32 imageEvent = debugInfo.profile.image_event;
// notify the debugger
debugInfo.profile.sample_count = 0;
+ debugInfo.profile.dropped_ticks = 0;
RELEASE_THREAD_LOCK();
enable_interrupts();
@@ -1303,6 +1261,7 @@ profiling_buffer_full(void*)
// prepare the message
debug_profiler_update message;
message.sample_count = sampleCount;
+ message.dropped_ticks = droppedTicks;
message.stack_depth = stackDepth;
message.image_event = imageEvent;
message.stopped = false;
@@ -1333,7 +1292,7 @@ profiling_event(timer* /*unused*/)
struct thread* thread = thread_get_current_thread();
thread_debug_info& debugInfo = thread->debug_info;
- bool flushBuffer;
+ bool flushBuffer = false;
if (profiling_do_sample(flushBuffer)) {
if (flushBuffer) {
// The sample buffer needs to be flushed; we'll have to notify the
@@ -1355,11 +1314,6 @@ profiling_event(timer* /*unused*/)
void
user_debug_thread_unscheduled(struct thread* thread)
{
- if (thread->debug_info.profile.disabled > 0) {
- ASSERT(thread->debug_info.profile.installed_timer == NULL);
- return;
- }
-
// if running, cancel the profiling timer
struct timer* timer = thread->debug_info.profile.installed_timer;
if (timer != NULL) {
@@ -1377,9 +1331,6 @@ user_debug_thread_unscheduled(struct thread* thread)
void
user_debug_thread_scheduled(struct thread* thread)
{
- if (thread->debug_info.profile.disabled > 0)
- return;
-
if (thread->debug_info.profile.samples != NULL
&& !thread->debug_info.profile.buffer_full) {
// install profiling timer
@@ -2321,7 +2272,12 @@ debug_nub_thread(void *)
threadDebugInfo.profile.samples = (addr_t*)samples;
threadDebugInfo.profile.max_samples
= areaInfo.size / sizeof(addr_t);
+ threadDebugInfo.profile.flush_threshold
+ = threadDebugInfo.profile.max_samples
+ * B_DEBUG_PROFILE_BUFFER_FLUSH_THRESHOLD
+ / 100;
threadDebugInfo.profile.sample_count = 0;
+ threadDebugInfo.profile.dropped_ticks = 0;
threadDebugInfo.profile.stack_depth = stackDepth;
threadDebugInfo.profile.buffer_full = false;
threadDebugInfo.profile.interval_left = interval;
@@ -2369,6 +2325,7 @@ debug_nub_thread(void *)
int32 sampleCount = 0;
int32 stackDepth = 0;
int32 imageEvent = 0;
+ int32 droppedTicks = 0;
// get the thread and detach the profile info
cpu_status state = disable_interrupts();
@@ -2382,11 +2339,13 @@ debug_nub_thread(void *)
sampleArea = threadDebugInfo.profile.sample_area;
samples = threadDebugInfo.profile.samples;
sampleCount = threadDebugInfo.profile.sample_count;
+ droppedTicks = threadDebugInfo.profile.dropped_ticks;
stackDepth = threadDebugInfo.profile.stack_depth;
imageEvent = threadDebugInfo.profile.image_event;
threadDebugInfo.profile.sample_area = -1;
threadDebugInfo.profile.samples = NULL;
threadDebugInfo.profile.buffer_full = false;
+ threadDebugInfo.profile.dropped_ticks = 0;
} else
result = B_BAD_VALUE;
} else
@@ -2401,6 +2360,7 @@ debug_nub_thread(void *)
reply.profiler_update.image_event = imageEvent;
reply.profiler_update.stack_depth = stackDepth;
reply.profiler_update.sample_count = sampleCount;
+ reply.profiler_update.dropped_ticks = droppedTicks;
reply.profiler_update.stopped = true;
} else
reply.profiler_update.origin.thread = result;