libcontainer: Add support for the "pausing" status #1704
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The freezer controller distinguishes between freezing and frozen [1]. We've had a "Pausing" since dbb515f (Update api proposal, 2014-07-08), but had never implemented it. This commit adds the missing implementation. I haven't updated libcontainer/cgroups, which has used a blocking freeze change since 3e8849f (implement wait on freeze, 2014-06-04). The cgroups interface doesn't distinguish between blocking and non-blocking sets, so there's no way to say "I want to start freezing, but don't need to block until completion". I haven't added integration tests either. All of our current tests (state.bats and pause.bats) assume a complete transition to 'paused'. That makes sense because 'runc pause ...' is based on the blocking libcontainer/cgroups implementation. The only way to see 'pausing' would be to have a parallel state call during the pause call. Here's how the timing could work out: 1. Call 'pause'. 2. Call 'state', which reads THAWED and outputs 'running' (or 'created', or whatever). 3. 'pause' starts freezing the controller. 4. Call 'state', which reads FREEZING and outputs 'pausing'. 5. 'pause' finishes freezing the controller. 6. Call 'state', which reads FROZEN and outputs 'paused'. 7. 'pause' exits. I'm not sure how to get a test where the 'state' call consistently fires at 4 and not at 2 or 6. [1]: https://www.kernel.org/doc/Documentation/cgroup-v1/freezer-subsystem.txt Signed-off-by: W. Trevor King <wking@tremily.us>
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We've removed "pausing" state in PR #3360 |
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Builds on #1703; review that first.
The freezer controller distinguishes between freezing and frozen. We've had a
Pausingsince dbb515f (2014-07-08), but had never implemented it. This pull-request adds the missing implementation.I haven't updated
libcontainer/cgroups, which has used a blocking freeze change since 3e8849f (2014-06-04). The cgroups interface doesn't distinguish between blocking and non-blocking sets, so there's no way to say “I want to start freezing, but don't need to block until completion”.I haven't added integration tests either. All of our current tests (
state.batsandpause.bats) assume a complete transition topaused. That makes sense becauserunc pause …is based on the blockinglibcontainer/cgroupsimplementation. The only way to seepausingwould be to have a parallel state call during the pause call. Here's how the timing could work out:pause.state, which readsTHAWEDand outputsrunning(orcreated, or whatever).pausestarts freezing the controller.state, which readsFREEZINGand outputspausing.pausefinishes freezing the controller.state, which readsFROZENand outputspaused.pauseexits.I'm not sure how to get a test where the
statecall consistently fires at 4 and not at 2 or 6.