On Wed, 2010-02-10 at 10:08 -0500, Dave Anderson wrote:
> ----- "Michael Holzheu" <holzheu@xxxxxxxxxxxxxxxxxx> wrote:
>
> > Hi again,
>
> > > When I change get_smp_cpus() to return "get_highest_cpu_online() + 1" I
> > > see five swapper idle tasks when using "ps". The problem I now have is
> > > that I have to provide a backtrace for the offline cpus. But the offline
> > > CPUs do not have any stack on s390. Is there a way to tell crash that
> > > there is no backtrace available? Probably I overlooked something...
> >
> > Ok, I think I got it now. In case of an offline CPU, I will use
> > "task_struct_thread_ksp" like I do it for non active tasks.
> >
> > When I do that I get for the swapper tasks with the offline CPUs:
> >
> > PID: 0 TASK: 18d38340 CPU: 2 COMMAND: "swapper"
> > #0 [18d3feb8] ret_from_fork at 117e12
> >
> > PID: 0 TASK: 18d40440 CPU: 3 COMMAND: "swapper"
> > #0 [18d47eb8] ret_from_fork at 117e12
>
> I'm not why you should do anything. The cpu is offline and for all
> practical purposes it doesn't exist, so why bother?
Because you can do a "bt" on the swapper task with the offline CPU.
Then s390x_get_stack_frame() is called where I figure out the stack
pointer and instruction address. In that function I check if the task is
currently running on a CPU and in that case I get the information from
the associated s390 lowcore, where the registers are stored in case of a
dump. If the task is not running I get the information from the thread
struct.
> The patch I have queued just uses get_highest_cpu_online()+1 and
> does nothing else. But I only tested it on a live system, and
> any backtrace attempt on the offlined swapper task just shows
> (active). What happens when you do a "bt -a" with a dumpfile?
It shows all swapper tasks (online and offline), but I get errors for
the backtrace for the offline CPUs.
The attached patch would solve the problem (and eliminate most of the
probably redundant s390(x)_has_cpu() function.
With this patch "ps" shows:
PID PPID CPU TASK ST %MEM VSZ RSS COMM
> 0 0 0 800ef0 RU 0.0 0 0 [swapper]
> 0 0 1 18d30240 RU 0.0 0 0 [swapper]
> 0 0 2 18d38340 RU 0.0 0 0 [swapper]
> 0 0 3 18d40440 RU 0.0 0 0 [swapper]
> 0 0 4 18d48540 RU 0.0 0 0 [swapper]
1 0 1 18d18040 IN 0.2 2244 1020 init
...
And "bt -a" shows:
PID: 0 TASK: 800ef0 CPU: 0 COMMAND: "swapper"
LOWCORE INFO:
-psw : 0x0706000180000000 0x0000000000115564
-function : vtime_stop_cpu at 115564
-prefix : 0x18d28000
-cpu timer: 0x7fff00c1 0x00c584ef
...
PID: 0 TASK: 18d30240 CPU: 1 COMMAND: "swapper"
LOWCORE INFO:
-psw : 0x0706000180000000 0x0000000000115564
-function : vtime_stop_cpu at 115564
...
PID: 0 TASK: 18d38340 CPU: 2 COMMAND: "swapper"
#0 [18d3feb8] ret_from_fork at 117e12
...
PID: 0 TASK: 18d40440 CPU: 3 COMMAND: "swapper"
#0 [18d47eb8] ret_from_fork at 117e12
...
PID: 0 TASK: 18d48540 CPU: 4 COMMAND: "swapper"
LOWCORE INFO:
-psw : 0x0706000180000000 0x0000000000115564
-function : vtime_stop_cpu at 115564
-prefix : 0x1416a000
Michael
---
s390.c | 57 ++++++++++++++-------------------------------------------
s390x.c | 57 ++++++++++++++-------------------------------------------
2 files changed, 28 insertions(+), 86 deletions(-)
--- a/s390.c
+++ b/s390.c
@@ -542,46 +542,17 @@ s390_cpu_of_task(unsigned long task)
}
/*
- * returns true, if task currently is executed by a cpu
+ * returns true, if task of bt currently is executed by a cpu
*/
static int
-s390_has_cpu(unsigned long task)
+s390_has_cpu(struct bt_info *bt)
{
- if(VALID_MEMBER(task_struct_cpus_runnable)){
- /* Linux 2.4 */
- unsigned long cpus_runnable;
- readmem(task+OFFSET(task_struct_cpus_runnable),KVADDR,
- &cpus_runnable,sizeof(cpus_runnable),
- "cpus_runnable", FAULT_ON_ERROR);
- if(cpus_runnable != ~0U)
- return TRUE;
- else
- return FALSE;
- } else {
- /* Linux 2.6 */
- unsigned long runqueue_addr, runqueue_offset;
- unsigned long cpu_offset, per_cpu_offset_addr, running_task;
- char *runqueue;
- int cpu;
-
- cpu = s390_cpu_of_task(task);
- runqueue = GETBUF(SIZE(runqueue));
-
- runqueue_offset=symbol_value("per_cpu__runqueues");
- per_cpu_offset_addr=symbol_value("__per_cpu_offset");
- readmem(per_cpu_offset_addr + cpu * sizeof(long),KVADDR,
- &cpu_offset, sizeof(long),"per_cpu_offset",
- FAULT_ON_ERROR);
- runqueue_addr=runqueue_offset + cpu_offset;
- readmem(runqueue_addr,KVADDR,runqueue,SIZE(runqueue),
- "runqueue", FAULT_ON_ERROR);
- running_task = ULONG(runqueue + OFFSET(runqueue_curr));
- FREEBUF(runqueue);
- if(running_task == task)
- return TRUE;
- else
- return FALSE;
- }
+ int cpu = bt->tc->processor;
+
+ if (is_task_active(bt->task) && (kt->cpu_flags[cpu] & ONLINE))
+ return TRUE;
+ else
+ return FALSE;
}
/*
@@ -635,7 +606,7 @@ s390_back_trace_cmd(struct bt_info *bt)
ksp = bt->stkptr;
/* print lowcore and get async stack when task has cpu */
- if(s390_has_cpu(bt->task)){
+ if(s390_has_cpu(bt)){
char lowcore[LOWCORE_SIZE];
unsigned long psw_flags;
int cpu = s390_cpu_of_task(bt->task);
@@ -687,7 +658,7 @@ s390_back_trace_cmd(struct bt_info *bt)
stack = bt->stackbuf;
stack_base = stack_start;
} else if((backchain > async_start) && (backchain < async_end)
- && s390_has_cpu(bt->task)){
+ && s390_has_cpu(bt)){
stack = async_stack;
stack_base = async_start;
} else {
@@ -903,12 +874,12 @@ s390_get_stack_frame(struct bt_info *bt,
int r14_offset;
char lowcore[LOWCORE_SIZE];
- if(s390_has_cpu(bt->task))
+ if(s390_has_cpu(bt))
s390_get_lowcore(s390_cpu_of_task(bt->task),lowcore);
/* get the stack pointer */
if(esp){
- if(s390_has_cpu(bt->task)){
+ if(s390_has_cpu(bt)){
ksp = ULONG(lowcore + MEMBER_OFFSET("_lowcore",
"gpregs_save_area") + (15 * S390_WORD_SIZE));
} else {
@@ -926,7 +897,7 @@ s390_get_stack_frame(struct bt_info *bt,
if(!eip)
return;
- if(s390_has_cpu(bt->task) && esp){
+ if(s390_has_cpu(bt) && esp){
*eip = ULONG(lowcore + OFFSET(s390_lowcore_psw_save_area) +
S390_WORD_SIZE) & S390_ADDR_MASK;
} else {
@@ -1015,7 +986,7 @@ s390_dis_filter(ulong vaddr, char *inbuf
int
s390_get_smp_cpus(void)
{
- return get_cpus_online();
+ return (get_highest_cpu_online() + 1);
}
/*
--- a/s390x.c
+++ b/s390x.c
@@ -554,46 +554,17 @@ s390x_cpu_of_task(unsigned long task)
}
/*
- * returns true, if task currently is executed by a cpu
+ * returns true, if task of bt currently is executed by a cpu
*/
static int
-s390x_has_cpu(unsigned long task)
+s390x_has_cpu(struct bt_info *bt)
{
- if(VALID_MEMBER(task_struct_cpus_runnable)){
- /* Linux 2.4 */
- unsigned long cpus_runnable;
- readmem(task+OFFSET(task_struct_cpus_runnable),KVADDR,
- &cpus_runnable,sizeof(cpus_runnable),
- "cpus_runnable", FAULT_ON_ERROR);
- if(cpus_runnable != ~0ULL)
- return TRUE;
- else
- return FALSE;
- } else {
- /* Linux 2.6 */
- unsigned long runqueue_addr, runqueue_offset;
- unsigned long cpu_offset, per_cpu_offset_addr, running_task;
- char *runqueue;
- int cpu;
-
- cpu = s390x_cpu_of_task(task);
- runqueue = GETBUF(SIZE(runqueue));
-
- runqueue_offset=symbol_value("per_cpu__runqueues");
- per_cpu_offset_addr=symbol_value("__per_cpu_offset");
- readmem(per_cpu_offset_addr + cpu * sizeof(long),KVADDR,
- &cpu_offset, sizeof(long),"per_cpu_offset",
- FAULT_ON_ERROR);
- runqueue_addr=runqueue_offset + cpu_offset;
- readmem(runqueue_addr,KVADDR,runqueue,SIZE(runqueue),
- "runqueue", FAULT_ON_ERROR);
- running_task = ULONG(runqueue + OFFSET(runqueue_curr));
- FREEBUF(runqueue);
- if(running_task == task)
- return TRUE;
- else
- return FALSE;
- }
+ int cpu = bt->tc->processor;
+
+ if (is_task_active(bt->task) && (kt->cpu_flags[cpu] & ONLINE))
+ return TRUE;
+ else
+ return FALSE;
}
/*
@@ -647,7 +618,7 @@ s390x_back_trace_cmd(struct bt_info *bt)
ksp = bt->stkptr;
/* print lowcore and get async stack when task has cpu */
- if(s390x_has_cpu(bt->task)){
+ if(s390x_has_cpu(bt)){
char lowcore[LOWCORE_SIZE];
unsigned long psw_flags;
int cpu = s390x_cpu_of_task(bt->task);
@@ -700,7 +671,7 @@ s390x_back_trace_cmd(struct bt_info *bt)
stack = bt->stackbuf;
stack_base = stack_start;
} else if((backchain > async_start) && (backchain < async_end)
- && s390x_has_cpu(bt->task)){
+ && s390x_has_cpu(bt)){
stack = async_stack;
stack_base = async_start;
} else {
@@ -936,12 +907,12 @@ s390x_get_stack_frame(struct bt_info *bt
int r14_offset;
char lowcore[LOWCORE_SIZE];
- if(s390x_has_cpu(bt->task))
+ if(s390x_has_cpu(bt))
s390x_get_lowcore(s390x_cpu_of_task(bt->task),lowcore);
/* get the stack pointer */
if(esp){
- if(s390x_has_cpu(bt->task)){
+ if(s390x_has_cpu(bt)){
ksp = ULONG(lowcore + MEMBER_OFFSET("_lowcore",
"gpregs_save_area") + (15 * S390X_WORD_SIZE));
} else {
@@ -959,7 +930,7 @@ s390x_get_stack_frame(struct bt_info *bt
if(!eip)
return;
- if(s390x_has_cpu(bt->task) && esp){
+ if(s390x_has_cpu(bt) && esp){
*eip = ULONG(lowcore + OFFSET(s390_lowcore_psw_save_area) +
S390X_WORD_SIZE);
} else {
@@ -1048,7 +1019,7 @@ s390x_dis_filter(ulong vaddr, char *inbu
int
s390x_get_smp_cpus(void)
{
- return get_cpus_online();
+ return (get_highest_cpu_online() + 1);
}
/*
--
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