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From: Fiona Ebner <f.ebner@proxmox.com>
To: pve-devel@lists.proxmox.com
Subject: [pve-devel] [PATCH v2 qemu-server 1/4] qmeventd: improve getting VMID from PID in presence of legacy cgroup entries
Date: Mon, 10 Jul 2023 10:52:59 +0200	[thread overview]
Message-ID: <20230710085302.27606-1-f.ebner@proxmox.com> (raw)

On a hybrid cgroup system, the /proc/<PID>/cgroup file looks like

> 13:pids:/qemu.slice/110.scope
> 12:perf_event:/
> 11:devices:/qemu.slice
> 10:misc:/
> 9:hugetlb:/
> 8:freezer:/
> 7:cpu,cpuacct:/qemu.slice/110.scope
> 6:memory:/qemu.slice/110.scope
> 5:rdma:/
> 4:cpuset:/
> 3:blkio:/qemu.slice
> 2:net_cls,net_prio:/
> 1:name=systemd:/qemu.slice/110.scope
> 0::/qemu.slice/110.scope

but the order doesn't seem to be deterministic, so it can happen that
an entry like '11:devices:/qemu.slice' is the first to match the
'/qemu.slice' part, which previously made the code expect to find the
VMID.

To improve detection, as a first step, match the trailing slash too.

Reported in the community forum:
https://forum.proxmox.com/threads/129320/post-571654

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---

Changes in v2:
    * Improve commit message, seems like the order is not the same on
      every boot.

 qmeventd/qmeventd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/qmeventd/qmeventd.c b/qmeventd/qmeventd.c
index 921c0dca..503bce69 100644
--- a/qmeventd/qmeventd.c
+++ b/qmeventd/qmeventd.c
@@ -109,7 +109,7 @@ get_vmid_from_pid(pid_t pid)
 	}
 	cgroup_path++;
 
-	if (strncmp(cgroup_path, "/qemu.slice", 11)) {
+	if (strncmp(cgroup_path, "/qemu.slice/", 12)) {
 	    continue;
 	}
 
@@ -142,7 +142,7 @@ get_vmid_from_pid(pid_t pid)
     if (errno) {
 	fprintf(stderr, "error parsing vmid for %d: %s\n", pid, strerror(errno));
     } else {
-	fprintf(stderr, "error parsing vmid for %d: no qemu.slice cgroup entry\n", pid);
+	fprintf(stderr, "error parsing vmid for %d: no matching qemu.slice cgroup entry\n", pid);
     }
 
 ret:
-- 
2.39.2





             reply	other threads:[~2023-07-10  8:53 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-10  8:52 Fiona Ebner [this message]
2023-07-10  8:53 ` [pve-devel] [PATCH v2 qemu-server 2/4] qmeventd: further improve getting VMID from PID Fiona Ebner
2023-07-10  8:53 ` [pve-devel] [PATCH v2 qemu-server 3/4] qmeventd: VMID from PID: don't fail immediately when encountering unexpected entry Fiona Ebner
2023-07-10  8:53 ` [pve-devel] [PATCH v2 qemu-server 4/4] qmeventd: VMID from PID: avoid goto Fiona Ebner
2023-07-17  9:40 ` [pve-devel] applied-series: [PATCH v2 qemu-server 1/4] qmeventd: improve getting VMID from PID in presence of legacy cgroup entries Wolfgang Bumiller

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