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OpenZFS 9425 - channel programs can be interrupted

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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
This commit is contained in:
Don Brady
2019-06-22 16:51:46 -07:00
committed by Brian Behlendorf
parent cb9e5b7e84
commit 186898bbb5
13 changed files with 322 additions and 97 deletions
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include/sys/txg.h
+5
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@@ -87,6 +87,11 @@ extern void txg_kick(struct dsl_pool *dp);
*/
extern void txg_wait_synced(struct dsl_pool *dp, uint64_t txg);
/*
* Wait as above. Returns true if the thread was signaled while waiting.
*/
extern boolean_t txg_wait_synced_sig(struct dsl_pool *dp, uint64_t txg);
/*
* Wait until the given transaction group, or one after it, is
* the open transaction group. Try to make this happen as soon