From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/fs/eventfd.c | 19 ++++++++++++-------
1 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/kernel/fs/eventfd.c b/kernel/fs/eventfd.c
index 8f017bd..3673eb8 100644
--- a/kernel/fs/eventfd.c
+++ b/kernel/fs/eventfd.c
@@ -25,6 +25,8 @@
#include <linux/idr.h>
#include <linux/uio.h>
+DEFINE_PER_CPU(int, eventfd_wake_count);
+
static DEFINE_IDA(eventfd_ida);
struct eventfd_ctx {
@@ -51,21 +53,21 @@
* Deadlock or stack overflow issues can happen if we recurse here
* through waitqueue wakeup handlers. If the caller users potentially
* nested waitqueues with custom wakeup handlers, then it should
- * check eventfd_signal_allowed() before calling this function. If
- * it returns false, the eventfd_signal() call should be deferred to a
+ * check eventfd_signal_count() before calling this function. If
+ * it returns true, the eventfd_signal() call should be deferred to a
* safe context.
*/
- if (WARN_ON_ONCE(current->in_eventfd_signal))
+ if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count)))
return 0;
spin_lock_irqsave(&ctx->wqh.lock, flags);
- current->in_eventfd_signal = 1;
+ this_cpu_inc(eventfd_wake_count);
if (ULLONG_MAX - ctx->count < n)
n = ULLONG_MAX - ctx->count;
ctx->count += n;
if (waitqueue_active(&ctx->wqh))
wake_up_locked_poll(&ctx->wqh, EPOLLIN | mask);
- current->in_eventfd_signal = 0;
+ this_cpu_dec(eventfd_wake_count);
spin_unlock_irqrestore(&ctx->wqh.lock, flags);
return n;
@@ -185,11 +187,14 @@
return events;
}
-static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
+void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
{
- *cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
+ lockdep_assert_held(&ctx->wqh.lock);
+
+ *cnt = ((ctx->flags & EFD_SEMAPHORE) && ctx->count) ? 1 : ctx->count;
ctx->count -= *cnt;
}
+EXPORT_SYMBOL_GPL(eventfd_ctx_do_read);
/**
* eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
--
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