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proc: add some (hopefully) insightful comments

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* /proc/${pid}/net status
* removing PDE vs last close stuff (again!)
* random small stuff

Link: https://lkml.kernel.org/r/YtwrM6sDC0OQ53YB@localhost.localdomain
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan
2022-07-23 20:09:07 +03:00
committed by akpm
parent fa7d574ba4
commit ed8fb78d7e
4 changed files with 27 additions and 5 deletions
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17
fs/proc/inode.c
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@ -212,7 +212,15 @@ static void unuse_pde(struct proc_dir_entry *pde)
complete(pde->pde_unload_completion);
}
/* pde is locked on entry, unlocked on exit */
/*
* At most 2 contexts can enter this function: the one doing the last
* close on the descriptor and whoever is deleting PDE itself.
*
* First to enter calls ->proc_release hook and signals its completion
* to the second one which waits and then does nothing.
*
* PDE is locked on entry, unlocked on exit.
*/
static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
__releases(&pde->pde_unload_lock)
{
@ -222,9 +230,6 @@ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
*
* rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
* "struct file" needs to be available at the right moment.
*
* Therefore, first process to enter this function does ->release() and
* signals its completion to the other process which does nothing.
*/
if (pdeo->closing) {
/* somebody else is doing that, just wait */
@ -238,10 +243,12 @@ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
pdeo->closing = true;
spin_unlock(&pde->pde_unload_lock);
file = pdeo->file;
pde->proc_ops->proc_release(file_inode(file), file);
spin_lock(&pde->pde_unload_lock);
/* After ->release. */
/* Strictly after ->proc_release, see above. */
list_del(&pdeo->lh);
c = pdeo->c;
spin_unlock(&pde->pde_unload_lock);