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mm: enable MMU_GATHER_RCU_TABLE_FREE for sh-X2

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Currently, non-x2 sh specifies CONFIG_MMU_GATHER_RCU_TABLE_FREE allowing
RCU page table freeing.

sh-X2 is problematic because it utilises slab-allocated PMD page tables,
and thus tlb_remove_ptdesc() cannot be used in these cases.

All other sh variants are fine as commit e3ecf7c7d0 ("mm: pgtable:
convert some architectures to use tlb_remove_ptdesc()") already converted
page table freeing to use tlb_remove_ptdesc(), which does so after an RCU
grace period when CONFIG_MMU_GATHER_RCU_TABLE_FREE is specified.

Resolve this issue by firstly specifying CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE
for sh-X2, so the arch can provide its own __tlb_remove_table()
implementation (called after the RCU grace period).

Then, convert __pmd_free_tlb() to tag the pointer to the PMD, and have
__tlb_remove_table() check this tag to determine whether to free via the
slab or to use pagetable_dtor_free().

This follows the pattern used by sparc64 as implemented in commit
4a0100f754 ("sparc64: use RCU page table freeing").

Previously __pmd_free_tlb() freed PMD page tables immediately, before any
TLB flush IPI.  This seems to be a pre-existing bug, which this change
also resolves.

CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE is only specified for sh-X2, as setting
it disables CONFIG_PT_RECLAIM and causes __tlb_remove_table_one() to call
tlb_remove_table_sync_rcu() and synchronize_rcu() in turn, and this is not
necessary for other sh variants.

This forms part of an overall effort to switch every architecture to this
mode.

Link: https://lore.kernel.org/20260925-rcu-pagetable-freeing-v5-8-31e91065fea4@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: Lance Yang <lance.yang@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Nico Pache <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Guo Ren <guoren@kernel.org>
Cc: Brian Cain <bcain@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Simon Schuster <schuster.simon@siemens-energy.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Rich Felker <dalias@libc.org>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Magnus Lindholm <linmag7@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: James Bottomley <james.bottomley@hansenpartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Christophe Leroy <chleroy@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Richard Weinberger <richard@nod.at>
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Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Qi Zheng <qi.zheng@linux.dev>
This commit is contained in:
Lorenzo Stoakes (ARM) 2026-09-25 21:09:43 +01:00 committed by Andrew Morton
parent ccdaaf5916
commit a72df94511
3 changed files with 27 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/sh/Kconfig
View File

@ -33,6 +33,7 @@ config SUPERH
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_KGDB
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TLB_REMOVE_TABLE if X2TLB
select HAVE_ARCH_TRACEHOOK
select HAVE_DEBUG_BUGVERBOSE
select HAVE_DEBUG_KMEMLEAK
@ -61,7 +62,7 @@ config SUPERH
select HAVE_SYSCALL_TRACEPOINTS
select IRQ_FORCED_THREADING
select LOCK_MM_AND_FIND_VMA
select MMU_GATHER_RCU_TABLE_FREE if MMU && !X2TLB
select MMU_GATHER_RCU_TABLE_FREE if MMU
select MODULES_USE_ELF_RELA
select NEED_SG_DMA_LENGTH
select NO_DMA if !MMU && !DMA_COHERENT

6
arch/sh/include/asm/pgalloc.h
View File

@ -17,7 +17,11 @@ extern void pgd_free(struct mm_struct *mm, pgd_t *pgd);
extern void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd);
extern pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address);
extern void pmd_free(struct mm_struct *mm, pmd_t *pmd);
#define __pmd_free_tlb(tlb, pmdp, addr) pmd_free((tlb)->mm, (pmdp))
extern void __tlb_remove_table(void *table);
/* PMDs are slab-allocated, tag so they are freed correctly. */
#define __pmd_free_tlb(tlb, pmdp, addr) \
tlb_remove_table((tlb), (void *)((unsigned long)(pmdp) | 1))
#endif
static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd,

20
arch/sh/mm/pgtable.c
View File

@ -56,4 +56,24 @@ void pmd_free(struct mm_struct *mm, pmd_t *pmd)
{
kmem_cache_free(pmd_cachep, pmd);
}
static void __tlb_remove_table_slab(void *table)
{
kmem_cache_free(pmd_cachep, table);
}
static void __tlb_remove_table_pgtable(void *table)
{
pagetable_dtor_free(table);
}
void __tlb_remove_table(void *table)
{
const unsigned long addr = (unsigned long)table;
if (addr & 1)
__tlb_remove_table_slab((void *)(addr & ~1UL));
else
__tlb_remove_table_pgtable(table);
}
#endif /* PAGETABLE_LEVELS > 2 */