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From: Paolo Bonzini <pbonzini@redhat.com>
To: He Zhe <zhe.he@windriver.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Juri Lelli <jlelli@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: 5.13-rt1 + KVM = WARNING: at fs/eventfd.c:74 eventfd_signal()
Date: Thu, 15 Jul 2021 11:51:32 +0200	[thread overview]
Message-ID: <b73f8986-9071-6fbb-5c6a-d7892ba2302b@redhat.com> (raw)
In-Reply-To: <ab85cd9e-f389-0641-8084-cdfbc5c91e0b@windriver.com>

On 15/07/21 10:44, He Zhe wrote:
> It was to increase the recursion depth to 2 so that vhost_worker and
> kvm_vcpu_ioctl syscall could work in parallel

The count is per-CPU, so parallel operations cannot cause it to become 
2.  Your patch might fix calls from ioeventfd to vhost_worker to another 
eventfd, but not *parallel* operation of KVM and vhost (except on 
PREEMPT_RT).

You should identify the exact callstack that caused the warning for 
vDUSE, and document that one in the commit message, so that reviewers 
can understand the issue.

Paolo


  reply	other threads:[~2021-07-15  9:51 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-14  8:01 5.13-rt1 + KVM = WARNING: at fs/eventfd.c:74 eventfd_signal() Daniel Bristot de Oliveira
2021-07-14  8:10 ` Paolo Bonzini
2021-07-14  9:23   ` Jason Wang
2021-07-14 10:35     ` Paolo Bonzini
2021-07-14 10:41       ` Michael S. Tsirkin
2021-07-14 10:44         ` Paolo Bonzini
2021-07-14 12:20       ` Daniel Bristot de Oliveira
2021-07-15  4:14       ` Jason Wang
2021-07-15  5:58         ` Paolo Bonzini
2021-07-15  6:45           ` Jason Wang
2021-07-15  8:22       ` Daniel Bristot de Oliveira
2021-07-15  8:44         ` He Zhe
2021-07-15  9:51           ` Paolo Bonzini [this message]
2021-07-15 10:10             ` He Zhe
2021-07-15 11:05               ` Paolo Bonzini
2021-07-16  2:26                 ` Jason Wang
2021-07-16  2:43                   ` He Zhe
2021-07-16  2:46                     ` Jason Wang
2021-07-15  9:46         ` Paolo Bonzini
2021-07-15 12:34           ` Daniel Bristot de Oliveira
     [not found]       ` <20210715102249.2205-1-hdanton@sina.com>
2021-07-15 12:31         ` Daniel Bristot de Oliveira
     [not found]         ` <20210716020611.2288-1-hdanton@sina.com>
2021-07-16  6:54           ` Paolo Bonzini
     [not found]           ` <20210716075539.2376-1-hdanton@sina.com>
2021-07-16  7:59             ` Paolo Bonzini
     [not found]             ` <20210716093725.2438-1-hdanton@sina.com>
2021-07-16 11:55               ` Paolo Bonzini
2021-07-18 12:42                 ` Hillf Danton
2021-07-19 15:38                   ` Paolo Bonzini
2021-07-21  7:04                     ` Hillf Danton
2021-07-21  7:25                       ` Thomas Gleixner
2021-07-21 10:11                         ` Hillf Danton
2021-07-21 10:59                           ` Paolo Bonzini
2021-07-22  5:58                             ` Hillf Danton
2021-07-23  2:23                             ` Hillf Danton
2021-07-23  7:59                               ` Paolo Bonzini
2021-07-23  9:48                                 ` Hillf Danton
2021-07-23 10:56                                   ` Paolo Bonzini
2021-07-24  4:33                                     ` Hillf Danton
2021-07-26 11:03                                       ` Paolo Bonzini
2021-07-28  8:06       ` Thomas Gleixner
2021-07-28 10:21         ` Paolo Bonzini
2021-07-28 19:07           ` Thomas Gleixner
2021-07-29 11:01             ` [PATCH] eventfd: Make signal recursion protection a task bit Thomas Gleixner
2021-07-29 14:32               ` Daniel Bristot de Oliveira
2021-07-29 19:23               ` Daniel Bristot de Oliveira
2021-08-26  7:03               ` Jason Wang
2021-08-27 23:41               ` [tip: sched/core] " tip-bot2 for Thomas Gleixner

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