The patch titled
eventfd: use waitqueue lock
has been added to the -mm tree. Its filename is
eventfd-use-waitqueue-lock.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: eventfd: use waitqueue lock
From: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
The eventfd was using the unlocked waitqueue operations, but it was using a
different lock, so poll_wait() would race with it. This patch makes
eventfd directly use the waitqueue lock.
Signed-off-by: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
Cc: Davi Arnaut <davi@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/eventfd.c | 26 ++++++++++++--------------
1 files changed, 12 insertions(+), 14 deletions(-)
diff -puN fs/eventfd.c~eventfd-use-waitqueue-lock fs/eventfd.c
--- a/fs/eventfd.c~eventfd-use-waitqueue-lock
+++ a/fs/eventfd.c
@@ -17,7 +17,6 @@
#include <linux/eventfd.h>
struct eventfd_ctx {
- spinlock_t lock;
wait_queue_head_t wqh;
/*
* Every time that a write(2) is performed on an eventfd, the
@@ -45,13 +44,13 @@ int eventfd_signal(struct file *file, in
if (n < 0)
return -EINVAL;
- spin_lock_irqsave(&ctx->lock, flags);
+ spin_lock_irqsave(&ctx->wqh.lock, flags);
if (ULLONG_MAX - ctx->count < n)
n = (int) (ULLONG_MAX - ctx->count);
ctx->count += n;
if (waitqueue_active(&ctx->wqh))
wake_up_locked(&ctx->wqh);
- spin_unlock_irqrestore(&ctx->lock, flags);
+ spin_unlock_irqrestore(&ctx->wqh.lock, flags);
return n;
}
@@ -70,14 +69,14 @@ static unsigned int eventfd_poll(struct
poll_wait(file, &ctx->wqh, wait);
- spin_lock_irqsave(&ctx->lock, flags);
+ spin_lock_irqsave(&ctx->wqh.lock, flags);
if (ctx->count > 0)
events |= POLLIN;
if (ctx->count == ULLONG_MAX)
events |= POLLERR;
if (ULLONG_MAX - 1 > ctx->count)
events |= POLLOUT;
- spin_unlock_irqrestore(&ctx->lock, flags);
+ spin_unlock_irqrestore(&ctx->wqh.lock, flags);
return events;
}
@@ -92,7 +91,7 @@ static ssize_t eventfd_read(struct file
if (count < sizeof(ucnt))
return -EINVAL;
- spin_lock_irq(&ctx->lock);
+ spin_lock_irq(&ctx->wqh.lock);
res = -EAGAIN;
ucnt = ctx->count;
if (ucnt > 0)
@@ -110,9 +109,9 @@ static ssize_t eventfd_read(struct file
res = -ERESTARTSYS;
break;
}
- spin_unlock_irq(&ctx->lock);
+ spin_unlock_irq(&ctx->wqh.lock);
schedule();
- spin_lock_irq(&ctx->lock);
+ spin_lock_irq(&ctx->wqh.lock);
}
__remove_wait_queue(&ctx->wqh, &wait);
__set_current_state(TASK_RUNNING);
@@ -122,7 +121,7 @@ static ssize_t eventfd_read(struct file
if (waitqueue_active(&ctx->wqh))
wake_up_locked(&ctx->wqh);
}
- spin_unlock_irq(&ctx->lock);
+ spin_unlock_irq(&ctx->wqh.lock);
if (res > 0 && put_user(ucnt, (__u64 __user *) buf))
return -EFAULT;
@@ -143,7 +142,7 @@ static ssize_t eventfd_write(struct file
return -EFAULT;
if (ucnt == ULLONG_MAX)
return -EINVAL;
- spin_lock_irq(&ctx->lock);
+ spin_lock_irq(&ctx->wqh.lock);
res = -EAGAIN;
if (ULLONG_MAX - ctx->count > ucnt)
res = sizeof(ucnt);
@@ -159,9 +158,9 @@ static ssize_t eventfd_write(struct file
res = -ERESTARTSYS;
break;
}
- spin_unlock_irq(&ctx->lock);
+ spin_unlock_irq(&ctx->wqh.lock);
schedule();
- spin_lock_irq(&ctx->lock);
+ spin_lock_irq(&ctx->wqh.lock);
}
__remove_wait_queue(&ctx->wqh, &wait);
__set_current_state(TASK_RUNNING);
@@ -171,7 +170,7 @@ static ssize_t eventfd_write(struct file
if (waitqueue_active(&ctx->wqh))
wake_up_locked(&ctx->wqh);
}
- spin_unlock_irq(&ctx->lock);
+ spin_unlock_irq(&ctx->wqh.lock);
return res;
}
@@ -210,7 +209,6 @@ asmlinkage long sys_eventfd(unsigned int
return -ENOMEM;
init_waitqueue_head(&ctx->wqh);
- spin_lock_init(&ctx->lock);
ctx->count = count;
/*
_
Patches currently in -mm which might be from davidel@xxxxxxxxxxxxxxx are
origin.patch
x86_64-fix-oprofile-smp.patch
eventfd-use-waitqueue-lock.patch
timerfd-use-waitqueue-lock.patch
-
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