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Re: [PATCH 1/2] xen: privcmd: Switch from mutex to spinlock for irqfds
- To: Viresh Kumar <viresh.kumar@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
- From: Juergen Gross <jgross@xxxxxxxx>
- Date: Tue, 2 Jul 2024 12:12:45 +0200
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- Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>, Alex Bennée <alex.bennee@xxxxxxxxxx>, Manos Pitsidianakis <manos.pitsidianakis@xxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Al Viro <viro@xxxxxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
- Delivery-date: Tue, 02 Jul 2024 10:12:52 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 18.06.24 11:42, Viresh Kumar wrote:
irqfd_wakeup() gets EPOLLHUP, when it is called by
eventfd_release() by way of wake_up_poll(&ctx->wqh, EPOLLHUP), which
gets called under spin_lock_irqsave(). We can't use a mutex here as it
will lead to a deadlock.
Fix it by switching over to a spin lock.
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
drivers/xen/privcmd.c | 26 +++++++++++++++-----------
1 file changed, 15 insertions(+), 11 deletions(-)
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 67dfa4778864..5ceb6c56cf3e 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -13,7 +13,6 @@
#include <linux/file.h>
#include <linux/kernel.h>
#include <linux/module.h>
-#include <linux/mutex.h>
I don't think you can drop that. There is still the ioreq_lock mutex.
I can fix that up while committing, with that:
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Juergen
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