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FROMLIST: cfi: free old cfi shadow asynchronously

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Currenly, it uses synchronize_rcu() to wait old rcu reader to go away
in update_shadow.In embedded platform like ARM CA7X,
load_module blocks 40~50ms in update_shadow.
When there are more than one hundred kernel modules,
it blocks several seconds.

To accelerate load_module,change synchronize_rcu to call_rcu.

Change-Id: I08dcb29ef97453b836efd0d64286196600be8cce
Signed-off-by: Haibo Li <haibo.li@mediatek.com>
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Link: https://lore.kernel.org/lkml/20220704014046.34596-3-haibo.li@mediatek.com/
Bug: 236922027
Bug: 257362811
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Haibo Li
2022-07-04 09:40:46 +08:00
committed by Todd Kjos
parent 0dd64a860c
commit aec27eb797
1 changed files with 10 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
kernel/cfi.c
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@@ -43,6 +43,8 @@ typedef u16 shadow_t;
struct cfi_shadow {
/* Page index for the beginning of the shadow */
unsigned long base;
/* rcu to free old cfi_shadow asynchronously */
struct rcu_head rcu;
/* An array of __cfi_check locations (as indices to the shadow) */
shadow_t shadow[1];
} __packed;
@@ -182,6 +184,13 @@ static void remove_module_from_shadow(struct cfi_shadow *s, struct module *mod,
}
}
static void free_shadow(struct rcu_head *rcu)
{
struct cfi_shadow *old = container_of(rcu, struct cfi_shadow, rcu);
vfree(old);
}
typedef void (*update_shadow_fn)(struct cfi_shadow *, struct module *,
unsigned long min_addr, unsigned long max_addr);
@@ -211,11 +220,10 @@ static void update_shadow(struct module *mod, unsigned long base_addr,
rcu_assign_pointer(cfi_shadow, next);
mutex_unlock(&shadow_update_lock);
synchronize_rcu();
if (prev) {
set_memory_rw((unsigned long)prev, SHADOW_PAGES);
vfree(prev);
call_rcu(&prev->rcu, free_shadow);
}
}