| Message ID | 20190418084253.142712304@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | stacktrace: Consolidate stack trace usage | expand |
On Thu, Apr 18, 2019 at 10:41:20AM +0200, Thomas Gleixner wrote: > - Remove the extra array member of stack_dump_trace[]. It's not required as > the stack tracer stores at max array size - 1 entries so there is still > an empty slot. What is the empty slot used for?
On Thu, 18 Apr 2019, Josh Poimboeuf wrote: > On Thu, Apr 18, 2019 at 10:41:20AM +0200, Thomas Gleixner wrote: > > - Remove the extra array member of stack_dump_trace[]. It's not required as > > the stack tracer stores at max array size - 1 entries so there is still > > an empty slot. > > What is the empty slot used for? I was trying to find an answer but failed. Maybe it's just historical leftovers or Steven knows where the magic is in this maze. Thanks, tglx
On Thu, 18 Apr 2019 23:14:45 +0200 (CEST) Thomas Gleixner <tglx@linutronix.de> wrote: > On Thu, 18 Apr 2019, Josh Poimboeuf wrote: > > > On Thu, Apr 18, 2019 at 10:41:20AM +0200, Thomas Gleixner wrote: > > > - Remove the extra array member of stack_dump_trace[]. It's not required as > > > the stack tracer stores at max array size - 1 entries so there is still > > > an empty slot. > > > > What is the empty slot used for? > > I was trying to find an answer but failed. Maybe it's just historical > leftovers or Steven knows where the magic is in this maze. > I believe it was for historical leftovers (there was a time it was required), and left there for "paranoid" sake. But let me apply the patch and see if it is really needed. -- Steve
On Thu, 18 Apr 2019 17:24:43 -0400 Steven Rostedt <rostedt@goodmis.org> wrote: > I believe it was for historical leftovers (there was a time it was > required), and left there for "paranoid" sake. But let me apply the > patch and see if it is really needed. I removed the +1 on the max_entries and set SET_TRACE_ENTRIES to 5 (a bit extreme). Then I ran the stack tracing with KASAN enabled and it never complained. As stated, it was there for historical reasons and I felt 500 was way more than enough and left the buffer there just out of laziness and paranoia. Feel free to remove that if you want. -- Steve
On Thu, 18 Apr 2019 10:41:20 +0200 Thomas Gleixner <tglx@linutronix.de> wrote: > @@ -412,23 +404,20 @@ stack_trace_sysctl(struct ctl_table *tab > void __user *buffer, size_t *lenp, > loff_t *ppos) > { > - int ret; > + int ret, was_enabled; One small nit. Could this be: int was_enabled; int ret; I prefer only joining variables that are related on the same line. Makes it look cleaner IMO. > > mutex_lock(&stack_sysctl_mutex); > + was_enabled = !!stack_tracer_enabled; > Bah, not sure why I didn't do it this way to begin with. I think I copied something else that couldn't do it this way for some reason and didn't put any brain power behind the copy. :-/ But that was back in 2008 so I blame it on being "young and stupid" ;-) Other then the above nit and removing the unneeded +1 in max_entries: Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> -- Steve > ret = proc_dointvec(table, write, buffer, lenp, ppos); > > - if (ret || !write || > - (last_stack_tracer_enabled == !!stack_tracer_enabled)) > + if (ret || !write || (was_enabled == !!stack_tracer_enabled)) > goto out; > > - last_stack_tracer_enabled = !!stack_tracer_enabled; > - > if (stack_tracer_enabled) > register_ftrace_function(&trace_ops); > else > unregister_ftrace_function(&trace_ops); > - > out: > mutex_unlock(&stack_sysctl_mutex); > return ret; > @@ -444,7 +433,6 @@ static __init int enable_stacktrace(char > strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE); > > stack_tracer_enabled = 1; > - last_stack_tracer_enabled = 1; > return 1; > } > __setup("stacktrace", enable_stacktrace); >
On Thu, 18 Apr 2019, Steven Rostedt wrote: > On Thu, 18 Apr 2019 10:41:20 +0200 > Thomas Gleixner <tglx@linutronix.de> wrote: > > > @@ -412,23 +404,20 @@ stack_trace_sysctl(struct ctl_table *tab > > void __user *buffer, size_t *lenp, > > loff_t *ppos) > > { > > - int ret; > > + int ret, was_enabled; > > One small nit. Could this be: > > int was_enabled; > int ret; > > I prefer only joining variables that are related on the same line. > Makes it look cleaner IMO. If you wish so. To me it's waste of screen space :) > > > > mutex_lock(&stack_sysctl_mutex); > > + was_enabled = !!stack_tracer_enabled; > > > > Bah, not sure why I didn't do it this way to begin with. I think I > copied something else that couldn't do it this way for some reason and > didn't put any brain power behind the copy. :-/ But that was back in > 2008 so I blame it on being "young and stupid" ;-) The young part is gone for sure :) > Other then the above nit and removing the unneeded +1 in max_entries: s/+1/-1/ Thanks, tglx
On Fri, 19 Apr 2019 00:44:17 +0200 (CEST) Thomas Gleixner <tglx@linutronix.de> wrote: > On Thu, 18 Apr 2019, Steven Rostedt wrote: > > On Thu, 18 Apr 2019 10:41:20 +0200 > > Thomas Gleixner <tglx@linutronix.de> wrote: > > > > > @@ -412,23 +404,20 @@ stack_trace_sysctl(struct ctl_table *tab > > > void __user *buffer, size_t *lenp, > > > loff_t *ppos) > > > { > > > - int ret; > > > + int ret, was_enabled; > > > > One small nit. Could this be: > > > > int was_enabled; > > int ret; > > > > I prefer only joining variables that are related on the same line. > > Makes it look cleaner IMO. > > If you wish so. To me it's waste of screen space :) At least you didn't say it helps the compiler ;-) > > > > > > > mutex_lock(&stack_sysctl_mutex); > > > + was_enabled = !!stack_tracer_enabled; > > > > > > > Bah, not sure why I didn't do it this way to begin with. I think I > > copied something else that couldn't do it this way for some reason and > > didn't put any brain power behind the copy. :-/ But that was back in > > 2008 so I blame it on being "young and stupid" ;-) > > The young part is gone for sure :) I purposely set you up for that response. > > > Other then the above nit and removing the unneeded +1 in max_entries: > > s/+1/-1/ That was an ode to G+ -- Steve
--- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -241,21 +241,11 @@ static inline void ftrace_free_mem(struc #ifdef CONFIG_STACK_TRACER -#define STACK_TRACE_ENTRIES 500 - -struct stack_trace; - -extern unsigned stack_trace_index[]; -extern struct stack_trace stack_trace_max; -extern unsigned long stack_trace_max_size; -extern arch_spinlock_t stack_trace_max_lock; - extern int stack_tracer_enabled; -void stack_trace_print(void); -int -stack_trace_sysctl(struct ctl_table *table, int write, - void __user *buffer, size_t *lenp, - loff_t *ppos); + +int stack_trace_sysctl(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos); /* DO NOT MODIFY THIS VARIABLE DIRECTLY! */ DECLARE_PER_CPU(int, disable_stack_tracer); --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -18,8 +18,10 @@ #include "trace.h" -static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES + 1]; -unsigned stack_trace_index[STACK_TRACE_ENTRIES]; +#define STACK_TRACE_ENTRIES 500 + +static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES]; +static unsigned stack_trace_index[STACK_TRACE_ENTRIES]; /* * Reserve one entry for the passed in ip. This will allow @@ -31,17 +33,16 @@ struct stack_trace stack_trace_max = { .entries = &stack_dump_trace[0], }; -unsigned long stack_trace_max_size; -arch_spinlock_t stack_trace_max_lock = +static unsigned long stack_trace_max_size; +static arch_spinlock_t stack_trace_max_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; DEFINE_PER_CPU(int, disable_stack_tracer); static DEFINE_MUTEX(stack_sysctl_mutex); int stack_tracer_enabled; -static int last_stack_tracer_enabled; -void stack_trace_print(void) +static void print_max_stack(void) { long i; int size; @@ -61,16 +62,7 @@ void stack_trace_print(void) } } -/* - * When arch-specific code overrides this function, the following - * data should be filled up, assuming stack_trace_max_lock is held to - * prevent concurrent updates. - * stack_trace_index[] - * stack_trace_max - * stack_trace_max_size - */ -void __weak -check_stack(unsigned long ip, unsigned long *stack) +static void check_stack(unsigned long ip, unsigned long *stack) { unsigned long this_size, flags; unsigned long *p, *top, *start; static int tracer_frame; @@ -179,7 +171,7 @@ check_stack(unsigned long ip, unsigned l stack_trace_max.nr_entries = x; if (task_stack_end_corrupted(current)) { - stack_trace_print(); + print_max_stack(); BUG(); } @@ -412,23 +404,20 @@ stack_trace_sysctl(struct ctl_table *tab void __user *buffer, size_t *lenp, loff_t *ppos) { - int ret; + int ret, was_enabled; mutex_lock(&stack_sysctl_mutex); + was_enabled = !!stack_tracer_enabled; ret = proc_dointvec(table, write, buffer, lenp, ppos); - if (ret || !write || - (last_stack_tracer_enabled == !!stack_tracer_enabled)) + if (ret || !write || (was_enabled == !!stack_tracer_enabled)) goto out; - last_stack_tracer_enabled = !!stack_tracer_enabled; - if (stack_tracer_enabled) register_ftrace_function(&trace_ops); else unregister_ftrace_function(&trace_ops); - out: mutex_unlock(&stack_sysctl_mutex); return ret; @@ -444,7 +433,6 @@ static __init int enable_stacktrace(char strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE); stack_tracer_enabled = 1; - last_stack_tracer_enabled = 1; return 1; } __setup("stacktrace", enable_stacktrace);
- Remove the extra array member of stack_dump_trace[]. It's not required as the stack tracer stores at max array size - 1 entries so there is still an empty slot. - Make variables which are only used in trace_stack.c static. - Simplify the enable/disable logic. - Rename stack_trace_print() as it's using the stack_trace_ namespace. Free the name up for stack trace related functions. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> --- V2: Add more cleanups and use print_max_stack() as requested by Steven. --- include/linux/ftrace.h | 18 ++++-------------- kernel/trace/trace_stack.c | 36 ++++++++++++------------------------ 2 files changed, 16 insertions(+), 38 deletions(-)