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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 Tony Hutter
parent cbb9154958
commit e625030c11
13 changed files with 323 additions and 97 deletions
Download Patch File Download Diff File Expand all files Collapse all files
module/zfs/txg.c
+33 -3
View File
@@ -675,8 +675,8 @@ txg_delay(dsl_pool_t *dp, uint64_t txg, hrtime_t delay, hrtime_t resolution)
mutex_exit(&tx->tx_sync_lock);
}
void
txg_wait_synced(dsl_pool_t *dp, uint64_t txg)
static boolean_t
txg_wait_synced_impl(dsl_pool_t *dp, uint64_t txg, boolean_t wait_sig)
{
tx_state_t *tx = &dp->dp_tx;
@@ -695,9 +695,39 @@ txg_wait_synced(dsl_pool_t *dp, uint64_t txg)
"tx_synced=%llu waiting=%llu dp=%p\n",
tx->tx_synced_txg, tx->tx_sync_txg_waiting, dp);
cv_broadcast(&tx->tx_sync_more_cv);
cv_wait_io(&tx->tx_sync_done_cv, &tx->tx_sync_lock);
if (wait_sig) {
/*
* Condition wait here but stop if the thread receives a
* signal. The caller may call txg_wait_synced*() again
* to resume waiting for this txg.
*/
if (cv_wait_io_sig(&tx->tx_sync_done_cv,
&tx->tx_sync_lock) == 0) {
mutex_exit(&tx->tx_sync_lock);
return (B_TRUE);
}
} else {
cv_wait_io(&tx->tx_sync_done_cv, &tx->tx_sync_lock);
}
}
mutex_exit(&tx->tx_sync_lock);
return (B_FALSE);
}
void
txg_wait_synced(dsl_pool_t *dp, uint64_t txg)
{
VERIFY0(txg_wait_synced_impl(dp, txg, B_FALSE));
}
/*
* Similar to a txg_wait_synced but it can be interrupted from a signal.
* Returns B_TRUE if the thread was signaled while waiting.
*/
boolean_t
txg_wait_synced_sig(dsl_pool_t *dp, uint64_t txg)
{
return (txg_wait_synced_impl(dp, txg, B_TRUE));
}
/*