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ap_tools/ap-check: handle get-attributes between pre and post event

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Since mdevctl commit acf78c1ff6c9 it is now possible for the
get-attributes event to occur between a pre-define and post-define.
This is done in order to obtain the active attributes for the device
before writing them to the config file, and implies that the
get-attributes cannot re-obtain the file lock.  For other cases
where mdevctl calls get-attributes, the file lock is not already
held and must be obtained by ap-check before reading attributes from
active devices.
To solve this, let's use the knowledge that mdevctl is a single-threaded
tool and add a test to detect this scenario.  If the file lock is
already held by the parent during a get-attributes, don't attempt to
re-acquire it.

Reported-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
This commit is contained in:
Matthew Rosato
2023-10-25 11:55:49 -04:00
committed by Steffen Eiden
parent af730c79a6
commit 55fdb17b18
3 changed files with 56 additions and 5 deletions
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ap_tools/ap-check.c
+27 -5
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@@ -798,12 +798,34 @@ static int ap_check_handle_get_attributes(struct ap_check_anchor *anc)
FILE *f;
int rc;
rc = ap_get_lock_callout();
if (rc) {
fprintf(stderr, "Failed to acquire configuration lock %d\n", rc);
return -1;
/*
* For the get-attributes callout, we are typically called without the
* callout lock held. However, there is a particular scenario (define
* of an active mdev) where we may or may not be called with the lock
* already held on behalf of mdevctl, depending on the mdevctl version.
* Let's test for lock ownership first and, if already owned by the
* parent (mdevctl) proceed rather than waiting on the file lock.
*/
rc = ap_try_lock_callout();
switch (rc) {
case 0:
/* Lock acquired */
anc->cleanup_lock = true;
break;
case 1:
/* Lock held by parent -- trust the lock will remain held */
break;
default:
/* Lock not acquired or held by parent -- do a normal obtain */
rc = ap_get_lock_callout();
if (rc) {
fprintf(stderr,
"Failed to acquire configuration lock %d\n",
rc);
return -1;
}
anc->cleanup_lock = true;
}
anc->cleanup_lock = true;
/*
* Read the 'matrix' and 'control_domains' attributes to get the