Re: [Crash-utility] [PATCH v2] Fix "ps/vm" commands to display the memory usage for exiting tasks

When a task is exiting, usually kernel marks its flags as 'PF_EXITING', but even so, sometimes the mm_struct has not been freed, it might still be valid. For such tasks, the "ps/vm" commands won't display the memory usage. For example: crash> ps 47070 PID PPID CPU TASK ST %MEM VSZ RSS COMM 47070 1 0 ffff9ba7c4910000 UN 0.0 0 0 ra_ris.parse crash> vm 47070 PID: 47070 TASK: ffff9ba7c4910000 CPU: 0 COMMAND: "ra_ris.parse" MM PGD RSS TOTAL_VM 0 0 0k 0k To be honest, this is a corner case, but it has already occurred in actual production environments. Given that, let's allow the "ps/vm" commands to try to display the memory usage for this case, but it does not guarantee that it can work well at any time, which still depends on how far the mm_struct deconstruction has proceeded. With the patch: crash> ps 47070 PID PPID CPU TASK ST %MEM VSZ RSS COMM 47070 1 0 ffff9ba7c4910000 UN 90.8 38461228 31426444 ra_ris.parse crash> vm 47070 PID: 47070 TASK: ffff9ba7c4910000 CPU: 0 COMMAND: "ra_ris.parse" MM PGD RSS TOTAL_VM ffff9bad6e873840 ffff9baee0544000 31426444k 38461228k VMA START END FLAGS FILE ffff9bafdbe1d6c8 400000 8c5000 8000875 /data1/rishome/ra_cu_cn_412/sbin/ra_ris.parse ... Reported-by: Buland Kumar Singh <bsingh(a)redhat.com&gt; Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com&gt; --- memory.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/memory.c b/memory.c index 5d76c5d7fe6f..86ccec5e2bac 100644 --- a/memory.c +++ b/memory.c @@ -4792,10 +4792,11 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm) { struct task_context *tc; long rss = 0, rss_cache = 0; + int mm_count = 0; BZERO(tm, sizeof(struct task_mem_usage)); - if (IS_ZOMBIE(task) || IS_EXITING(task)) + if (IS_ZOMBIE(task)) return; tc = task_to_context(task); @@ -4808,6 +4809,11 @@ get_task_mem_usage(ulong task, struct task_mem_usage *tm) if (!task_mm(task, TRUE)) return; + mm_count = INT(tt->mm_struct + OFFSET(mm_struct_mm_count)); + + if (IS_EXITING(task) && mm_count <= 0) + return; + if (VALID_MEMBER(mm_struct_rss)) /* * mm_struct.rss or mm_struct._rss exist.