[lxc-devel] [lxc/master] Don't busy loop on freeze with cgroupv2
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lxc-bot at linuxcontainers.org
Fri May 15 13:17:53 UTC 2020
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From 9d1c51d19e4db3ea0ae2f7b1dfc9024e3e6b6d4d Mon Sep 17 00:00:00 2001
From: Wolfgang Bumiller <w.bumiller at proxmox.com>
Date: Fri, 15 May 2020 15:06:38 +0200
Subject: [PATCH 1/3] mainloop: add lxc_mainloop_add_handler_events
in order to be able to listen for EPOLLPRI
Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
---
src/lxc/mainloop.c | 15 ++++++++++++---
src/lxc/mainloop.h | 4 ++++
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/src/lxc/mainloop.c b/src/lxc/mainloop.c
index 6d4c5935ae..d5ae2a67a0 100644
--- a/src/lxc/mainloop.c
+++ b/src/lxc/mainloop.c
@@ -59,8 +59,10 @@ int lxc_mainloop(struct lxc_epoll_descr *descr, int timeout_ms)
}
}
-int lxc_mainloop_add_handler(struct lxc_epoll_descr *descr, int fd,
- lxc_mainloop_callback_t callback, void *data)
+int lxc_mainloop_add_handler_events(struct lxc_epoll_descr *descr, int fd,
+ int events,
+ lxc_mainloop_callback_t callback,
+ void *data)
{
__do_free struct mainloop_handler *handler = NULL;
__do_free struct lxc_list *item = NULL;
@@ -77,7 +79,7 @@ int lxc_mainloop_add_handler(struct lxc_epoll_descr *descr, int fd,
handler->fd = fd;
handler->data = data;
- ev.events = EPOLLIN;
+ ev.events = events;
ev.data.ptr = handler;
if (epoll_ctl(descr->epfd, EPOLL_CTL_ADD, fd, &ev) < 0)
@@ -92,6 +94,13 @@ int lxc_mainloop_add_handler(struct lxc_epoll_descr *descr, int fd,
return 0;
}
+int lxc_mainloop_add_handler(struct lxc_epoll_descr *descr, int fd,
+ lxc_mainloop_callback_t callback, void *data)
+{
+ return lxc_mainloop_add_handler_events(descr, fd, EPOLLIN, callback,
+ data);
+}
+
int lxc_mainloop_del_handler(struct lxc_epoll_descr *descr, int fd)
{
struct mainloop_handler *handler;
diff --git a/src/lxc/mainloop.h b/src/lxc/mainloop.h
index 8afac60d35..e6ab9a6d9e 100644
--- a/src/lxc/mainloop.h
+++ b/src/lxc/mainloop.h
@@ -22,6 +22,10 @@ typedef int (*lxc_mainloop_callback_t)(int fd, uint32_t event, void *data,
extern int lxc_mainloop(struct lxc_epoll_descr *descr, int timeout_ms);
+extern int lxc_mainloop_add_handler_events(struct lxc_epoll_descr *descr,
+ int fd, int events,
+ lxc_mainloop_callback_t callback,
+ void *data);
extern int lxc_mainloop_add_handler(struct lxc_epoll_descr *descr, int fd,
lxc_mainloop_callback_t callback,
void *data);
From 443be56560ee9b3c80d35d995520825e3c4c5672 Mon Sep 17 00:00:00 2001
From: Wolfgang Bumiller <w.bumiller at proxmox.com>
Date: Fri, 15 May 2020 15:07:07 +0200
Subject: [PATCH 2/3] cgfsng: deduplicate freeze code
Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
---
src/lxc/cgroups/cgfsng.c | 65 ++++++++++++----------------------------
1 file changed, 19 insertions(+), 46 deletions(-)
diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index 892fd915bb..7136d27a87 100644
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -2042,7 +2042,11 @@ static int freezer_cgroup_events_cb(int fd, uint32_t events, void *cbdata,
return LXC_MAINLOOP_CONTINUE;
}
-static int cg_unified_freeze(struct cgroup_ops *ops, int timeout)
+static int cg_unified_freeze_do(struct cgroup_ops *ops, int timeout,
+ const char *state_string,
+ int state_num,
+ const char *epoll_error,
+ const char *wait_error)
{
__do_close int fd = -EBADF;
call_cleaner(lxc_mainloop_close) struct lxc_epoll_descr *descr_ptr = NULL;
@@ -2067,26 +2071,33 @@ static int cg_unified_freeze(struct cgroup_ops *ops, int timeout)
ret = lxc_mainloop_open(&descr);
if (ret)
- return log_error_errno(-1, errno, "Failed to create epoll instance to wait for container freeze");
+ return log_error_errno(-1, errno, "%s", epoll_error);
/* automatically cleaned up now */
descr_ptr = &descr;
- ret = lxc_mainloop_add_handler(&descr, fd, freezer_cgroup_events_cb, INT_TO_PTR((int){1}));
+ ret = lxc_mainloop_add_handler(&descr, fd, freezer_cgroup_events_cb, INT_TO_PTR(state_num));
if (ret < 0)
return log_error_errno(-1, errno, "Failed to add cgroup.events fd handler to mainloop");
}
- ret = lxc_write_openat(h->container_full_path, "cgroup.freeze", "1", 1);
+ ret = lxc_write_openat(h->container_full_path, "cgroup.freeze", state_string, 1);
if (ret < 0)
return log_error_errno(-1, errno, "Failed to open cgroup.freeze file");
if (timeout != 0 && lxc_mainloop(&descr, timeout))
- return log_error_errno(-1, errno, "Failed to wait for container to be frozen");
+ return log_error_errno(-1, errno, "%s", wait_error);
return 0;
}
+static int cg_unified_freeze(struct cgroup_ops *ops, int timeout)
+{
+ return cg_unified_freeze_do(ops, timeout, "1", 1,
+ "Failed to create epoll instance to wait for container freeze",
+ "Failed to wait for container to be frozen");
+}
+
__cgfsng_ops static int cgfsng_freeze(struct cgroup_ops *ops, int timeout)
{
if (!ops->hierarchies)
@@ -2112,47 +2123,9 @@ static int cg_legacy_unfreeze(struct cgroup_ops *ops)
static int cg_unified_unfreeze(struct cgroup_ops *ops, int timeout)
{
- __do_close int fd = -EBADF;
- call_cleaner(lxc_mainloop_close)struct lxc_epoll_descr *descr_ptr = NULL;
- int ret;
- struct lxc_epoll_descr descr;
- struct hierarchy *h;
-
- h = ops->unified;
- if (!h)
- return ret_set_errno(-1, ENOENT);
-
- if (!h->container_full_path)
- return ret_set_errno(-1, EEXIST);
-
- if (timeout != 0) {
- __do_free char *events_file = NULL;
-
- events_file = must_make_path(h->container_full_path, "cgroup.events", NULL);
- fd = open(events_file, O_RDONLY | O_CLOEXEC);
- if (fd < 0)
- return log_error_errno(-1, errno, "Failed to open cgroup.events file");
-
- ret = lxc_mainloop_open(&descr);
- if (ret)
- return log_error_errno(-1, errno, "Failed to create epoll instance to wait for container unfreeze");
-
- /* automatically cleaned up now */
- descr_ptr = &descr;
-
- ret = lxc_mainloop_add_handler(&descr, fd, freezer_cgroup_events_cb, INT_TO_PTR((int){0}));
- if (ret < 0)
- return log_error_errno(-1, errno, "Failed to add cgroup.events fd handler to mainloop");
- }
-
- ret = lxc_write_openat(h->container_full_path, "cgroup.freeze", "0", 1);
- if (ret < 0)
- return log_error_errno(-1, errno, "Failed to open cgroup.freeze file");
-
- if (timeout != 0 && lxc_mainloop(&descr, timeout))
- return log_error_errno(-1, errno, "Failed to wait for container to be unfrozen");
-
- return 0;
+ return cg_unified_freeze_do(ops, timeout, "0", 0,
+ "Failed to create epoll instance to wait for container unfreeze",
+ "Failed to wait for container to be unfrozen");
}
__cgfsng_ops static int cgfsng_unfreeze(struct cgroup_ops *ops, int timeout)
From 385e58e8a8664d43175f64b8d44900ff651cec0f Mon Sep 17 00:00:00 2001
From: Wolfgang Bumiller <w.bumiller at proxmox.com>
Date: Fri, 15 May 2020 15:07:35 +0200
Subject: [PATCH 3/3] cgfsng: use EPOLLPRI when polling cgroup.events
EPOLLIN will always be true and therefore end up
busy-looping
Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
---
src/lxc/cgroups/cgfsng.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index 7136d27a87..f7af7c0a50 100644
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -27,6 +27,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <sys/epoll.h>
#include <sys/types.h>
#include <unistd.h>
@@ -2076,7 +2077,7 @@ static int cg_unified_freeze_do(struct cgroup_ops *ops, int timeout,
/* automatically cleaned up now */
descr_ptr = &descr;
- ret = lxc_mainloop_add_handler(&descr, fd, freezer_cgroup_events_cb, INT_TO_PTR(state_num));
+ ret = lxc_mainloop_add_handler_events(&descr, fd, EPOLLPRI, freezer_cgroup_events_cb, INT_TO_PTR(state_num));
if (ret < 0)
return log_error_errno(-1, errno, "Failed to add cgroup.events fd handler to mainloop");
}
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