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kernfs: handle null pointers while printing node name and path

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Null kernfs nodes could be found at cgroups during construction.
It seems safer to handle these null pointers right in kernfs in
the same way as printf prints "(null)" for null pointer string.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Konstantin Khlebnikov
2017-02-08 14:28:55 +03:00
committed by Greg Kroah-Hartman
parent 64e90a8acb
commit 17627157cd
2 changed files with 16 additions and 14 deletions
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20
include/trace/events/cgroup.h
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@@ -61,19 +61,15 @@ DECLARE_EVENT_CLASS(cgroup,
__field( int, id )
__field( int, level )
__dynamic_array(char, path,
cgrp->kn ? cgroup_path(cgrp, NULL, 0) + 1
: strlen("(null)"))
cgroup_path(cgrp, NULL, 0) + 1)
),
TP_fast_assign(
__entry->root = cgrp->root->hierarchy_id;
__entry->id = cgrp->id;
__entry->level = cgrp->level;
if (cgrp->kn)
cgroup_path(cgrp, __get_dynamic_array(path),
__get_dynamic_array_len(path));
else
__assign_str(path, "(null)");
cgroup_path(cgrp, __get_dynamic_array(path),
__get_dynamic_array_len(path));
),
TP_printk("root=%d id=%d level=%d path=%s",
@@ -119,8 +115,7 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
__field( int, dst_id )
__field( int, dst_level )
__dynamic_array(char, dst_path,
dst_cgrp->kn ? cgroup_path(dst_cgrp, NULL, 0) + 1
: strlen("(null)"))
cgroup_path(dst_cgrp, NULL, 0) + 1)
__field( int, pid )
__string( comm, task->comm )
),
@@ -129,11 +124,8 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
__entry->dst_root = dst_cgrp->root->hierarchy_id;
__entry->dst_id = dst_cgrp->id;
__entry->dst_level = dst_cgrp->level;
if (dst_cgrp->kn)
cgroup_path(dst_cgrp, __get_dynamic_array(dst_path),
__get_dynamic_array_len(dst_path));
else
__assign_str(dst_path, "(null)");
cgroup_path(dst_cgrp, __get_dynamic_array(dst_path),
__get_dynamic_array_len(dst_path));
__entry->pid = task->pid;
__assign_str(comm, task->comm);
),