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From:   Helge Deller <deller@gmx.de>
To:     linux@armlinux.org.uk, dinguyen@kernel.org,
        linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org
Cc:     Helge Deller <deller@gmx.de>
Subject: [PATCH 3/3] parisc: Fix flush_dcache_page() for usage from irq context
Date:   Wed, 24 May 2023 17:26:33 +0200
Message-Id: <20230524152633.203927-4-deller@gmx.de>
In-Reply-To: <20230524152633.203927-1-deller@gmx.de>
References: <20230524152633.203927-1-deller@gmx.de>
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Precedence: bulk

Since at least kernel 6.1, flush_dcache_page() is called with IRQs
disabled, e.g. from aio_complete().

But the current implementation for flush_dcache_page() on parisc
unintentionally re-enables IRQs, which may lead to deadlocks.

Fix it by using xa_lock_irqsave() and xa_unlock_irqrestore()
for the flush_dcache_mmap_*lock() macros instead.

Cc: linux-parisc@vger.kernel.org
Signed-off-by: Helge Deller <deller@gmx.de>
=2D--
 arch/parisc/include/asm/cacheflush.h | 4 ++++
 arch/parisc/kernel/cache.c           | 5 +++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/parisc/include/asm/cacheflush.h b/arch/parisc/include/as=
m/cacheflush.h
index 0bdee6724132..c8b6928cee1e 100644
=2D-- a/arch/parisc/include/asm/cacheflush.h
+++ b/arch/parisc/include/asm/cacheflush.h
@@ -48,6 +48,10 @@ void flush_dcache_page(struct page *page);

 #define flush_dcache_mmap_lock(mapping)		xa_lock_irq(&mapping->i_pages)
 #define flush_dcache_mmap_unlock(mapping)	xa_unlock_irq(&mapping->i_pages=
)
+#define flush_dcache_mmap_lock_irqsave(mapping, flags)		\
+		xa_lock_irqsave(&mapping->i_pages, flags)
+#define flush_dcache_mmap_unlock_irqrestore(mapping, flags)	\
+		xa_unlock_irqrestore(&mapping->i_pages, flags)

 #define flush_icache_page(vma,page)	do { 		\
 	flush_kernel_dcache_page_addr(page_address(page)); \
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 1d3b8bc8a623..ca4a302d4365 100644
=2D-- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -399,6 +399,7 @@ void flush_dcache_page(struct page *page)
 	unsigned long offset;
 	unsigned long addr, old_addr =3D 0;
 	unsigned long count =3D 0;
+	unsigned long flags;
 	pgoff_t pgoff;

 	if (mapping && !mapping_mapped(mapping)) {
@@ -420,7 +421,7 @@ void flush_dcache_page(struct page *page)
 	 * to flush one address here for them all to become coherent
 	 * on machines that support equivalent aliasing
 	 */
-	flush_dcache_mmap_lock(mapping);
+	flush_dcache_mmap_lock_irqsave(mapping, flags);
 	vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) {
 		offset =3D (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
 		addr =3D mpnt->vm_start + offset;
@@ -460,7 +461,7 @@ void flush_dcache_page(struct page *page)
 		}
 		WARN_ON(++count =3D=3D 4096);
 	}
-	flush_dcache_mmap_unlock(mapping);
+	flush_dcache_mmap_unlock_irqrestore(mapping, flags);
 }
 EXPORT_SYMBOL(flush_dcache_page);

=2D-
2.38.1