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OpenZFS 9425 - channel programs can be interrupted

Description

OpenZFS 9425 - channel programs can be interrupted

Problem Statement

ZFS Channel program scripts currently require a timeout, so that hung or
long-running scripts return a timeout error instead of causing ZFS to get
wedged. This limit can currently be set up to 100 million Lua instructions.
Even with a limit in place, it would be desirable to have a sys admin
(support engineer) be able to cancel a script that is taking a long time.

Proposed Solution

Make it possible to abort a channel program by sending an interrupt signal.In
the underlying txg_wait_sync function, switch the cv_wait to a cv_wait_sig to
catch the signal. Once a signal is encountered, the dsl_sync_task function can
install a Lua hook that will get called before the Lua interpreter executes a
new line of code. The dsl_sync_task can resume with a standard txg_wait_sync
call and wait for the txg to complete. Meanwhile, the hook will abort the
script and indicate that the channel program was canceled. The kernel returns
a EINTR to indicate that the channel program run was canceled.

Porting notes: Added missing return value from cv_wait_sig()

Authored by: Don Brady <don.brady@delphix.com>
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Sara Hartse <sara.hartse@delphix.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Robert Mustacchi <rm@joyent.com>
Ported-by: Don Brady <don.brady@delphix.com>
Signed-off-by: Don Brady <don.brady@delphix.com>

OpenZFS-issue: https://www.illumos.org/issues/9425
OpenZFS-commit: https://github.com/illumos/illumos-gate/commit/d0cb1fb926
Closes #8904

Details

Provenance
Don Brady <don.brady@delphix.com>Authored on Jun 22 2019, 11:51 PM
Brian Behlendorf <behlendorf1@llnl.gov>Committed on Jun 22 2019, 11:51 PM
Parents
rGcb9e5b7e8465: dn_struct_rwlock can not be held in dmu_tx_try_assign()
Branches
Unknown
Tags
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Event Timeline

Brian Behlendorf <behlendorf1@llnl.gov> committed rG186898bbb580: OpenZFS 9425 - channel programs can be interrupted (authored by Don Brady <don.brady@delphix.com>).Jun 22 2019, 11:51 PM