linux-kernel - [PATCH] md/raid5-ppl: Fix invalid context sleep in ppl_io_unit_finished() on PREEMPT

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Message-ID: <20250817113114.1335810-3-ysk@kzalloc.com>
Date: Sun, 17 Aug 2025 11:31:16 +0000
From: Yunseong Kim <ysk@...lloc.com>
To: Song Liu <song@...nel.org>,
	Yu Kuai <yukuai3@...wei.com>
Cc: linux-raid@...r.kernel.org,
	linux-rt-devel@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Yunseong Kim <ysk@...lloc.com>
Subject: [PATCH] md/raid5-ppl: Fix invalid context sleep in ppl_io_unit_finished() on PREEMPT_RT

The function ppl_io_unit_finished() uses a local_irq_save()/spin_lock()
sequence. On a PREEMPT_RT enabled kernel, spin_lock() can sleep. Calling it
with interrupts disabled creates an atomic context where sleeping is
forbidden.

Ensuring that the interrupt state is managed atomically with the lock
itself. The change is applied to both the 'log->io_list_lock' and
'ppl_conf->no_mem_stripes_lock' critical sections within the function.

Signed-off-by: Yunseong Kim <ysk@...lloc.com>
---
 drivers/md/raid5-ppl.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/md/raid5-ppl.c b/drivers/md/raid5-ppl.c
index 56b234683ee6..650bd59ead72 100644
--- a/drivers/md/raid5-ppl.c
+++ b/drivers/md/raid5-ppl.c
@@ -553,15 +553,13 @@ static void ppl_io_unit_finished(struct ppl_io_unit *io)
 
 	pr_debug("%s: seq: %llu\n", __func__, io->seq);
 
-	local_irq_save(flags);
-
-	spin_lock(&log->io_list_lock);
+	spin_lock_irqsave(&log->io_list_lock, flags);
 	list_del(&io->log_sibling);
-	spin_unlock(&log->io_list_lock);
+	spin_unlock_irqrestore(&log->io_list_lock, flags);
 
 	mempool_free(io, &ppl_conf->io_pool);
 
-	spin_lock(&ppl_conf->no_mem_stripes_lock);
+	spin_lock_irqsave(&ppl_conf->no_mem_stripes_lock, flags);
 	if (!list_empty(&ppl_conf->no_mem_stripes)) {
 		struct stripe_head *sh;
 
@@ -571,9 +569,7 @@ static void ppl_io_unit_finished(struct ppl_io_unit *io)
 		set_bit(STRIPE_HANDLE, &sh->state);
 		raid5_release_stripe(sh);
 	}
-	spin_unlock(&ppl_conf->no_mem_stripes_lock);
-
-	local_irq_restore(flags);
+	spin_unlock_irqrestore(&ppl_conf->no_mem_stripes_lock, flags);
 
 	wake_up(&conf->wait_for_quiescent);
 }
-- 
2.50.0