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Subject[Patch 1/3] ksym_tracer: Eliminate trace concatenation and machine stall issues post removal
This patch fixes two issues reported with ksym tracer, seen after
removal of a symbol from the tracer i) Concatenation of trace logs
into a single line ii) Machine stall seen when logs are viewed
using 'trace_pipe'.

Known issue: Upon removal, 'cat trace_pipe' (without any preceding
command and any further output in the trace buffer) responds to
SIGTERM quickly but only after an indeterminate amount of delay
for SIGINT.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
---
kernel/trace/trace.h | 12 +++++++++---
kernel/trace/trace_ksym.c | 11 ++++-------
2 files changed, 13 insertions(+), 10 deletions(-)

Index: linux-2.6-tip.hbkpt/kernel/trace/trace_ksym.c
===================================================================
--- linux-2.6-tip.hbkpt.orig/kernel/trace/trace_ksym.c
+++ linux-2.6-tip.hbkpt/kernel/trace/trace_ksym.c
@@ -71,7 +71,7 @@ void ksym_hbp_handler(struct hw_breakpoi
{
struct ring_buffer_event *event;
struct trace_array *tr;
- struct trace_ksym *entry;
+ struct trace_ksym_rb *entry;
int pc;

if (!ksym_tracing_enabled)
@@ -87,7 +87,7 @@ void ksym_hbp_handler(struct hw_breakpoi

entry = ring_buffer_event_data(event);
strlcpy(entry->ksym_name, hbp->info.name, KSYM_SYMBOL_LEN);
- entry->ksym_hbp = hbp;
+ memcpy(&(entry->ksym_hbp), hbp, sizeof(struct hw_breakpoint));
entry->ip = instruction_pointer(regs);
strlcpy(entry->p_name, current->comm, TASK_COMM_LEN);
#ifdef CONFIG_PROFILE_KSYM_TRACER
@@ -380,7 +380,7 @@ static enum print_line_t ksym_trace_outp
{
struct trace_entry *entry = iter->ent;
struct trace_seq *s = &iter->seq;
- struct trace_ksym *field;
+ struct trace_ksym_rb *field;
char str[KSYM_SYMBOL_LEN];
int ret;

@@ -394,17 +394,14 @@ static enum print_line_t ksym_trace_outp
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;

- switch (field->ksym_hbp->info.type) {
+ switch (field->ksym_hbp.info.type) {
case HW_BREAKPOINT_WRITE:
ret = trace_seq_printf(s, " W ");
break;
case HW_BREAKPOINT_RW:
ret = trace_seq_printf(s, " RW ");
break;
- default:
- return TRACE_TYPE_PARTIAL_LINE;
}
-
if (!ret)
return TRACE_TYPE_PARTIAL_LINE;

Index: linux-2.6-tip.hbkpt/kernel/trace/trace.h
===================================================================
--- linux-2.6-tip.hbkpt.orig/kernel/trace/trace.h
+++ linux-2.6-tip.hbkpt/kernel/trace/trace.h
@@ -216,15 +216,21 @@ struct syscall_trace_exit {
extern int process_new_ksym_entry(char *ksymname, int op, unsigned long addr);

struct trace_ksym {
- struct trace_entry ent;
struct hw_breakpoint *ksym_hbp;
unsigned long ksym_addr;
- unsigned long ip;
#ifdef CONFIG_PROFILE_KSYM_TRACER
unsigned long counter;
#endif
struct hlist_node ksym_hlist;
char ksym_name[KSYM_NAME_LEN];
+};
+
+/* Ring buffer's copy of the breakpoint data */
+struct trace_ksym_rb {
+ struct trace_entry ent;
+ struct hw_breakpoint ksym_hbp;
+ unsigned long ip;
+ char ksym_name[KSYM_NAME_LEN];
char p_name[TASK_COMM_LEN];
};

@@ -343,7 +349,7 @@ extern void __ftrace_bad_type(void);
TRACE_SYSCALL_ENTER); \
IF_ASSIGN(var, ent, struct syscall_trace_exit, \
TRACE_SYSCALL_EXIT); \
- IF_ASSIGN(var, ent, struct trace_ksym, TRACE_KSYM); \
+ IF_ASSIGN(var, ent, struct trace_ksym_rb, TRACE_KSYM); \
__ftrace_bad_type(); \
} while (0)



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