On Fri, 21 May 2021 12:01:54 +0900 Naoya Horiguchi <nao.horiguchi@xxxxxxxxx> wrote:
> There can be races when multiple CPUs consume poison from the same
> page. The first into memory_failure() atomically sets the HWPoison
> page flag and begins hunting for tasks that map this page. Eventually
> it invalidates those mappings and may send a SIGBUS to the affected
> tasks.
>
> But while all that work is going on, other CPUs see a "success"
> return code from memory_failure() and so they believe the error
> has been handled and continue executing.
>
> Fix by wrapping most of the internal parts of memory_failure() in
> a mutex.
We can reduce the scope of that mutex, which helps readability at least.
--- a/mm/memory-failure.c~mm-memory-failure-use-a-mutex-to-avoid-memory_failure-races-fix
+++ a/mm/memory-failure.c
@@ -1397,8 +1397,6 @@ out:
return rc;
}
-static DEFINE_MUTEX(mf_mutex);
-
/**
* memory_failure - Handle memory failure of a page.
* @pfn: Page Number of the corrupted page
@@ -1425,6 +1423,7 @@ int memory_failure(unsigned long pfn, in
int res = 0;
unsigned long page_flags;
bool retry = true;
+ static DEFINE_MUTEX(mf_mutex);
if (!sysctl_memory_failure_recovery)
panic("Memory failure on page %lx", pfn);
_
