The patch titled
Subject: proc/kcore: replace kclist_lock rwlock with rwsem
has been added to the -mm tree. Its filename is
proc-kcore-replace-kclist_lock-rwlock-with-rwsem.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-kcore-replace-kclist_lock-rwlock-with-rwsem.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-kcore-replace-kclist_lock-rwlock-with-rwsem.patch
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------------------------------------------------------
From: Omar Sandoval <osandov@xxxxxx>
Subject: proc/kcore: replace kclist_lock rwlock with rwsem
Now we only need kclist_lock from user context and at fs init time, and
the following changes need to sleep while holding the kclist_lock.
Link: http://lkml.kernel.org/r/783ba3becc424db45e5d5c93559fc40ef6173f01.1531440458.git.osandov@xxxxxx
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN fs/proc/kcore.c~proc-kcore-replace-kclist_lock-rwlock-with-rwsem fs/proc/kcore.c
--- a/fs/proc/kcore.c~proc-kcore-replace-kclist_lock-rwlock-with-rwsem
+++ a/fs/proc/kcore.c
@@ -59,8 +59,8 @@ struct memelfnote
};
static LIST_HEAD(kclist_head);
-static DEFINE_RWLOCK(kclist_lock);
-static int kcore_need_update = 1;
+static DECLARE_RWSEM(kclist_lock);
+static atomic_t kcore_need_update = ATOMIC_INIT(1);
/* This doesn't grab kclist_lock, so it should only be used at init time. */
void __init
@@ -117,8 +117,8 @@ static void __kcore_update_ram(struct li
struct kcore_list *tmp, *pos;
LIST_HEAD(garbage);
- write_lock(&kclist_lock);
- if (kcore_need_update) {
+ down_write(&kclist_lock);
+ if (atomic_cmpxchg(&kcore_need_update, 1, 0)) {
list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
if (pos->type == KCORE_RAM
|| pos->type == KCORE_VMEMMAP)
@@ -127,9 +127,8 @@ static void __kcore_update_ram(struct li
list_splice_tail(list, &kclist_head);
} else
list_splice(list, &garbage);
- kcore_need_update = 0;
proc_root_kcore->size = get_kcore_size(&nphdr, &size);
- write_unlock(&kclist_lock);
+ up_write(&kclist_lock);
free_kclist_ents(&garbage);
}
@@ -452,11 +451,11 @@ read_kcore(struct file *file, char __use
int nphdr;
unsigned long start;
- read_lock(&kclist_lock);
+ down_read(&kclist_lock);
size = get_kcore_size(&nphdr, &elf_buflen);
if (buflen == 0 || *fpos >= size) {
- read_unlock(&kclist_lock);
+ up_read(&kclist_lock);
return 0;
}
@@ -473,11 +472,11 @@ read_kcore(struct file *file, char __use
tsz = buflen;
elf_buf = kzalloc(elf_buflen, GFP_ATOMIC);
if (!elf_buf) {
- read_unlock(&kclist_lock);
+ up_read(&kclist_lock);
return -ENOMEM;
}
elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);
- read_unlock(&kclist_lock);
+ up_read(&kclist_lock);
if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
kfree(elf_buf);
return -EFAULT;
@@ -492,7 +491,7 @@ read_kcore(struct file *file, char __use
if (buflen == 0)
return acc;
} else
- read_unlock(&kclist_lock);
+ up_read(&kclist_lock);
/*
* Check to see if our file offset matches with any of
@@ -505,12 +504,12 @@ read_kcore(struct file *file, char __use
while (buflen) {
struct kcore_list *m;
- read_lock(&kclist_lock);
+ down_read(&kclist_lock);
list_for_each_entry(m, &kclist_head, list) {
if (start >= m->addr && start < (m->addr+m->size))
break;
}
- read_unlock(&kclist_lock);
+ up_read(&kclist_lock);
if (&m->list == &kclist_head) {
if (clear_user(buffer, tsz))
@@ -563,7 +562,7 @@ static int open_kcore(struct inode *inod
if (!filp->private_data)
return -ENOMEM;
- if (kcore_need_update)
+ if (atomic_read(&kcore_need_update))
kcore_update_ram();
if (i_size_read(inode) != proc_root_kcore->size) {
inode_lock(inode);
@@ -593,9 +592,8 @@ static int __meminit kcore_callback(stru
switch (action) {
case MEM_ONLINE:
case MEM_OFFLINE:
- write_lock(&kclist_lock);
- kcore_need_update = 1;
- write_unlock(&kclist_lock);
+ atomic_set(&kcore_need_update, 1);
+ break;
}
return NOTIFY_OK;
}
_
Patches currently in -mm which might be from osandov@xxxxxx are
proc-kcore-dont-grab-lock-for-kclist_add.patch
proc-kcore-replace-kclist_lock-rwlock-with-rwsem.patch
proc-kcore-fix-memory-hotplug-vs-multiple-opens-race.patch
proc-kcore-hold-lock-during-read.patch
proc-kcore-clean-up-elf-header-generation.patch
proc-kcore-optimize-multiple-page-reads.patch
proc-kcore-add-vmcoreinfo-note-to-proc-kcore.patch
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