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eventfd use waitqueue lock ... 

The eventfd was using the unlocked waitqueue operations, but it was
using a different lock, so poll_wait() would race with it.

This makes eventfd directly use the waitqueue lock.

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davide Libenzi 2007-05-18 12:02:33 -07:00 committed by Linus Torvalds
parent 347b4599dd
commit d48eb23315
1 changed files with 12 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
fs/eventfd.c
View File

@ -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, int n)
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 file *file, poll_table *wait)
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 *file, char __user *buf, size_t count,
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 *file, char __user *buf, size_t count,
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 *file, char __user *buf, size_t count,
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 *file, const char __user *buf, size_t c
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 *file, const char __user *buf, size_t c
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 *file, const char __user *buf, size_t c
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 count)
return -ENOMEM;
init_waitqueue_head(&ctx->wqh);
spin_lock_init(&ctx->lock);
ctx->count = count;
/*