diff options
| author | Aboorva Devarajan <aboorvad@linux.ibm.com> | 2025-12-01 11:30:09 +0530 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-01-14 22:16:21 -0800 |
| commit | b9efe36b5e3eb2e91aa3d706066428648af034fc (patch) | |
| tree | 46f5ceccdc32e967de2ca13192010767def4d935 /mm | |
| parent | a38be546269073bf8edc3c49eaf18cdfce905777 (diff) | |
mm/page_alloc: make percpu_pagelist_high_fraction reads lock-free
When page isolation loops indefinitely during memory offline, reading
/proc/sys/vm/percpu_pagelist_high_fraction blocks on pcp_batch_high_lock,
causing hung task warnings.
Make procfs reads lock-free since percpu_pagelist_high_fraction is a
simple integer with naturally atomic reads, writers still serialize via
the mutex.
This prevents hung task warnings when reading the procfs file during
long-running memory offline operations.
[akpm@linux-foundation.org: add comment, per Michal]
Link: https://lkml.kernel.org/r/aS_y9AuJQFydLEXo@tiehlicka
Link: https://lkml.kernel.org/r/20251201060009.1420792-1-aboorvad@linux.ibm.com
Signed-off-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_alloc.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c380f063e8b7..3dce96f3be49 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6667,11 +6667,19 @@ static int percpu_pagelist_high_fraction_sysctl_handler(const struct ctl_table * int old_percpu_pagelist_high_fraction; int ret; + /* + * Avoid using pcp_batch_high_lock for reads as the value is read + * atomically and a race with offlining is harmless. + */ + + if (!write) + return proc_dointvec_minmax(table, write, buffer, length, ppos); + mutex_lock(&pcp_batch_high_lock); old_percpu_pagelist_high_fraction = percpu_pagelist_high_fraction; ret = proc_dointvec_minmax(table, write, buffer, length, ppos); - if (!write || ret < 0) + if (ret < 0) goto out; /* Sanity checking to avoid pcp imbalance */ |