* seq_file calls stop() after show()
@ 2016-10-05 9:25 Gaurav Kalra
0 siblings, 0 replies; only message in thread
From: Gaurav Kalra @ 2016-10-05 9:25 UTC (permalink / raw)
To: kernelnewbies
Hi,
I am trying to duplicate the purpose of /proc/pid/io for a homework to
understand how procfs / seq_file works. Although there is no mandate to use
seq_file but it seems very interesting to me.
The aim is to print an output similar to /proc/pid/io but for all processes
at once using a custom proc file name "/proc/proc_io".
The project is organized as follows:
main.c -> It is responsible for kernel module init / deinit
sequence.c -> This is where I have put in the processing logic
utils.h -> bunch of macros for debugging
The debugging logs come as follows:
=========
[ +4.814129] <pl_open:15>
[ +0.000017] <pl_seq_start:53>
[ +0.000003] <pl_seq_start:55> init_task: [ffffffff81e11500] pos: [0]
[ +0.000001] <pl_seq_show:103>
[ +0.000004] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225a28000]
[ +0.000002] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225a28dc0]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225a29b80]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225a2b700]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225a2d280]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225a2e040]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225a2ee00]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225a78000]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225a7ee00]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225aa8000]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225aa8dc0]
[ +0.000001] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225aaa940]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225aab700]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225aac4c0]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225aad280]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225aaee00]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225048000]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff880225048dc0]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff880225049b80]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff88022504b700]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff88022504c4c0]
[ +0.000001] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff88022504d280]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff88022504e040]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff8802250f0000]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff8802250f0dc0]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff8802250f1b80]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff8802250f2940]
[ +0.000001] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff8802250f44c0]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff8802250f5280]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff8802250f6040]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff8802250f6e00]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_next:72>
[ +0.000001] <pl_seq_next:79> n_tsk: [ffff8802251a0dc0]
[ +0.000002] <pl_seq_show:103>
[ +0.000002] <pl_seq_next:72>
[ +0.000002] <pl_seq_next:79> n_tsk: [ffff8802251a1b80]
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_stop:92>
[ +0.000276] <pl_seq_start:53>
[ +0.000002] <pl_seq_start:55> init_task: [ffffffff81e11500] pos: [1]
[ +0.000001] <pl_seq_stop:92>
=========
Towards the end, the sequence is as follows:
[ +0.000001] <pl_seq_show:103>
[ +0.000003] <pl_seq_stop:92>
i.e. stop() is called after show().
This is making my output truncated to only first few processes.
Although I always return 0 from show(), I fail to understand why stop() is
being invoked just after show().
Can you please help me or redirect me somewhere to understand why this is
happening?
Thank You.
Gaurav
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2016-10-05 9:25 seq_file calls stop() after show() Gaurav Kalra
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