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From:   yaozhenguo <yaozhenguo1@gmail.com>
To:     tony.luck@intel.com, youquan.song@intel.com
Cc:     linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org,
        yaozhenguo@jd.com, yaozhenguo <yaozhenguo1@gmail.com>
Subject: [PATCH] mm,hwpoison: Don't call task_work_add when there is same work in the queue
Date:   Fri,  9 Jul 2021 17:28:18 +0800
Message-Id: <20210709092818.7795-1-yaozhenguo1@gmail.com>
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queue_task_work can be called more than once in one task before
this task work is running. it can lead to task->task_works becomes
an endless loop list and the task will never return to user mode.
Don't call task_work_add when there is same work in the queue.

Signed-off-by: yaozhenguo <yaozhenguo1@gmail.com>
---
 arch/x86/kernel/cpu/mce/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 22791aa..62c67ad 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1299,7 +1299,9 @@ static void queue_task_work(struct mce *m, int kill_current_task)
 	else
 		current->mce_kill_me.func = kill_me_maybe;
 
-	task_work_add(current, &current->mce_kill_me, TWA_RESUME);
+	/* Avoid endless loops in task_work_run */
+	if (READ_ONCE(current->task_works) != &current->mce_kill_me)
+		task_work_add(current, &current->mce_kill_me, TWA_RESUME);
 }
 
 /*
-- 
1.8.3.1