From: Ivan Kokshaysky <ink@unseen.parts>
To: Magnus Lindholm <linmag7@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org,
hch@infradead.org, macro@orcam.me.uk,
glaubitz@physik.fu-berlin.de, mattst88@gmail.com,
richard.henderson@linaro.org
Subject: Re: [PATCH 1/1] alpha: fix user-space corruption during memory compaction
Date: Sat, 3 Jan 2026 14:41:44 +0100 [thread overview]
Message-ID: <aVkcmDm1z5PGZNg6@minute> (raw)
In-Reply-To: <20260102173603.18247-2-linmag7@gmail.com>
On Fri, Jan 02, 2026 at 06:30:43PM +0100, Magnus Lindholm wrote:
> Alpha systems can suffer sporadic user-space crashes and heap
> corruption when memory compaction is enabled.
>
> Symptoms include SIGSEGV, glibc allocator failures (e.g. "unaligned
> tcache chunk"), and compiler internal errors. The failures disappear
> when compaction is disabled or when using global TLB invalidation.
>
> The root cause is insufficient TLB shootdown during page migration.
> Alpha relies on ASN-based MM context rollover for instruction cache
> coherency, but this alone is not sufficient to prevent stale data or
> instruction translations from surviving migration.
>
> Fix this by introducing a migration-specific helper that combines:
> - MM context invalidation (ASN rollover),
> - immediate per-CPU TLB invalidation (TBI),
> - synchronous cross-CPU shootdown when required.
>
> The helper is used only by migration/compaction paths to avoid changing
> global TLB semantics.
>
> Additionally, update flush_tlb_other(), pte_clear(), to use
> READ_ONCE()/WRITE_ONCE() for correct SMP memory ordering.
>
> This fixes observed crashes on both UP and SMP Alpha systems.
>
> Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
Impressive work! Spot on, I guess.
Reviewed-by: Ivan Kokshaysky <ink@unseen.parts>
Ivan.
next prev parent reply other threads:[~2026-01-03 14:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-02 17:30 [PATCH 0/1] alpha: fix user-space corruption during memory compaction Magnus Lindholm
2026-01-02 17:30 ` [PATCH 1/1] " Magnus Lindholm
2026-01-03 13:41 ` Ivan Kokshaysky [this message]
2026-01-10 23:50 ` matoro
2026-01-02 17:57 ` [PATCH 0/1] " John Paul Adrian Glaubitz
2026-01-20 7:44 ` Michael Cree
2026-01-20 22:44 ` Magnus Lindholm
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