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perf core: Generalize max_stack sysctl handler

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So that it can be used for other stack related knobs, such as the
upcoming one to tweak the max number of of contexts per stack sample.

In all those cases we can only change the value if there are no perf
sessions collecting stacks, so they need to grab that mutex, etc.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-8t3fk94wuzp8m2z1n4gc0s17@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2016-05-10 16:34:53 -03:00
parent 0a77582f04
commit a831100aee
2 changed files with 4 additions and 3 deletions
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5
kernel/events/callchain.c
View File

@ -228,7 +228,8 @@ exit_put:
int perf_event_max_stack_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
int new_value = sysctl_perf_event_max_stack, ret;
int *value = table->data;
int new_value = *value, ret;
struct ctl_table new_table = *table;
new_table.data = &new_value;
@ -240,7 +241,7 @@ int perf_event_max_stack_handler(struct ctl_table *table, int write,
if (atomic_read(&nr_callchain_events))
ret = -EBUSY;
else
sysctl_perf_event_max_stack = new_value;
*value = new_value;
mutex_unlock(&callchain_mutex);

2
kernel/sysctl.c
View File

@ -1149,7 +1149,7 @@ static struct ctl_table kern_table[] = {
},
{
.procname = "perf_event_max_stack",
.data = NULL, /* filled in by handler */
.data = &sysctl_perf_event_max_stack,
.maxlen = sizeof(sysctl_perf_event_max_stack),
.mode = 0644,
.proc_handler = perf_event_max_stack_handler,