From: Andrew Morton <akpm@linux-foundation.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: willy@infradead.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com,
kernel test robot <oliver.sang@intel.com>
Subject: Re: [PATCH] test_xarray: fix soft lockup for advanced-api tests
Date: Mon, 19 Feb 2024 18:28:08 -0800 [thread overview]
Message-ID: <20240219182808.726500bf3546b49ac05d98d4@linux-foundation.org> (raw)
In-Reply-To: <20240216194329.840555-1-mcgrof@kernel.org>
On Fri, 16 Feb 2024 11:43:29 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote:
> The new adanced API tests
So this is a fix against the mm-unstable series "test_xarray: advanced
API multi-index tests", v2.
> want to vet the xarray API is doing what it
> promises by manually iterating over a set of possible indexes on its
> own, and using a query operation which holds the RCU lock and then
> releases it. So it is not using the helper loop options which xarray
> provides on purpose. Any loop which iterates over 1 million entries
> (which is possible with order 20, so emulating say a 4 GiB block size)
> to just to rcu lock and unlock will eventually end up triggering a soft
> lockup on systems which don't preempt, and have lock provin and RCU
> prooving enabled.
>
> xarray users already use XA_CHECK_SCHED for loops which may take a long
> time, in our case we don't want to RCU unlock and lock as the caller
> does that already, but rather just force a schedule every XA_CHECK_SCHED
> iterations since the test is trying to not trust and rather test that
> xarray is doing the right thing.
>
> [0] https://lkml.kernel.org/r/202402071613.70f28243-lkp@intel.com
>
> Reported-by: kernel test robot <oliver.sang@intel.com>
As the above links shows, this should be
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202402071613.70f28243-lkp@intel.com
> --- a/lib/test_xarray.c
> +++ b/lib/test_xarray.c
> @@ -781,6 +781,7 @@ static noinline void *test_get_entry(struct xarray *xa, unsigned long index)
> {
> XA_STATE(xas, xa, index);
> void *p;
> + static unsigned int i = 0;
I don't think this needs static storage.
PetPeeve: it is unexpected that `i' has unsigned type. Can a more
communicative identifier be used?
I shall queue your patch as a fixup patch against
test_xarray-add-tests-for-advanced-multi-index-use and shall add the
below on top. Pleae check.
--- a/lib/test_xarray.c~test_xarray-fix-soft-lockup-for-advanced-api-tests-fix
+++ a/lib/test_xarray.c
@@ -728,7 +728,7 @@ static noinline void *test_get_entry(str
{
XA_STATE(xas, xa, index);
void *p;
- static unsigned int i = 0;
+ unsigned int loops = 0;
rcu_read_lock();
repeat:
@@ -746,7 +746,7 @@ repeat:
* APIs won't be stupid, proper page cache APIs loop over the proper
* order so when using a larger order we skip shared entries.
*/
- if (++i % XA_CHECK_SCHED == 0)
+ if (++loops % XA_CHECK_SCHED == 0)
schedule();
return p;
_
next prev parent reply other threads:[~2024-02-20 2:28 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-16 19:43 [PATCH] test_xarray: fix soft lockup for advanced-api tests Luis Chamberlain
2024-02-20 2:28 ` Andrew Morton [this message]
2024-02-20 17:45 ` Luis Chamberlain
2024-02-20 19:00 ` Andrew Morton
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