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Fri, 18 Sep 2026 07:54:56 +0000 X-Mizu-Trace-ID: ea360a8e458d95f5 X-Migadu-Flow: FLOW_OUT Date: Fri, 18 Sep 2026 15:54:48 +0800 From: Baoquan He To: Wandun Chen Cc: catalin.marinas@arm.com, will@kernel.org, chenhuacai@kernel.org, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, robh@kernel.org, saravanak@kernel.org, akpm@linux-foundation.org, rppt@kernel.org, pasha.tatashin@soleen.com, pratyush@kernel.org, m.szyprowski@samsung.com, mark.rutland@arm.com, kernel@xen0n.name, alex@ghiti.fr, hpa@zytor.com, ruirui.yang@linux.dev, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, iommu@lists.linux.dev Subject: Re: [PATCH v6 04/10] crash_core: serialize crash header preparation against hotplug Message-ID: References: <20260902073116.802752-1-chenwandun1@gmail.com> <20260902073116.802752-5-chenwandun1@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260902073116.802752-5-chenwandun1@gmail.com> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 95DC640004 X-Stat-Signature: hyidjwkwbbcftttzj3ey5kytdto56hs1 X-Rspam-User: X-HE-Tag: 1789718097-433341 X-HE-Meta: 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 BrgxozKk A0LU9/4IHLalQTGdoH6bpNcQsf+b7hekmxdHOuwHRHYSGU2OG/dncN0wgokf4fuWDYLAz/ib0G/v90MaW+ZF9qQI0gy5NXHUEk5MqNGtII/uxDHRYrObhb0i/p6ZZX36I9w3Np98Qde28jCz7HtvxiiGTfJrRbrW4nnIX3Nirbl5IYDnXRQsb3mSzCVq2wm14DZX6hzCKtEAb6qkGzk2BmfNiMW67ZLN2PBMYhR7xVYtmL2pRe+ssogWHGDAkdOBUmacOftV64SFyVVsT7hxv41+Vi16QUI8vJugsYktjM+MHlKbPVWvBlGQFwYN9yXCRzwpmSmrRirx1yPtxMAyKiF059xjj6oneJWm3rDe6nE2LIJjTv4bW9KAspS3Ori6qV7mXWzAH70/ReRraD3WnHY9hHJZ0pmLNyo0Wmy+qbrxflZFTjxWqX24JFCv58a/H5oXzr960irSV2aoomz/9BSH2xA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09/02/26 at 03:31pm, Wandun Chen wrote: > From: Wandun Chen > > crash_prepare_headers() counts memory ranges before populating the > allocated crash_mem array. The weak implementation used by ARM64, > RISC-V and LoongArch walks memblock.memory, while x86 performs the same > two-pass operation over system RAM resources. Concurrent memory hotplug > can change range source between the two walks and make the populate > pass overflow cmem->ranges. > > Take device_hotplug_lock when preparing crash headers during > kexec_file_load(). The x86 memory hotplug path already takes > device_hotplug_lock, so call __crash_prepare_headers() directly > to avoid recursive locking. > > Sashiko reported this issue in [1]. > > Fixes: 3751e728cef2 ("arm64: kexec_file: add crash dump support") > Fixes: 1bcca8620a91 ("LoongArch: Add crash dump support for kexec_file") > Fixes: 8acea455fafa ("RISC-V: Support for kexec_file on panic") > Fixes: dd5f726076cc ("kexec: support for kexec on panic using new system call") > Signed-off-by: Wandun Chen > Link: https://sashiko.dev/#/message/20260806101002.1F84E1F000E9@smtp.kernel.org [1] > --- > arch/x86/kernel/crash.c | 2 +- > include/linux/crash_core.h | 2 ++ > kernel/crash_core.c | 17 +++++++++++++++-- > 3 files changed, 18 insertions(+), 3 deletions(-) LGTM, Acked-by: Baoquan He > > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c > index e681ec9cf1dc..284d78bc3fd0 100644 > --- a/arch/x86/kernel/crash.c > +++ b/arch/x86/kernel/crash.c > @@ -465,7 +465,7 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) > * Create the new elfcorehdr reflecting the changes to CPU and/or > * memory resources. > */ > - if (crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz, NULL)) { > + if (__crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz, NULL)) { > pr_err("unable to create new elfcorehdr"); > goto out; > } > diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h > index bc087124cd78..28e7a81cf263 100644 > --- a/include/linux/crash_core.h > +++ b/include/linux/crash_core.h > @@ -61,6 +61,8 @@ extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_ma > void **addr, unsigned long *sz); > extern int crash_prepare_headers(int need_kernel_map, void **addr, > unsigned long *sz, unsigned long *nr_mem_ranges); > +int __crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, > + unsigned long *nr_mem_ranges); > extern int crash_exclude_core_ranges(struct crash_mem **cmem); > > struct kimage; > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > index 77285ae3ce60..3adee1ae120c 100644 > --- a/kernel/crash_core.c > +++ b/kernel/crash_core.c > @@ -16,6 +16,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -338,8 +339,8 @@ int crash_exclude_core_ranges(struct crash_mem **cmem) > return 0; > } > > -int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, > - unsigned long *nr_mem_ranges) > +int __crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, > + unsigned long *nr_mem_ranges) > { > unsigned int max_nr_ranges; > struct crash_mem *cmem; > @@ -376,6 +377,18 @@ int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, > return ret; > } > > +int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz, > + unsigned long *nr_mem_ranges) > +{ > + int ret; > + > + lock_device_hotplug(); > + ret = __crash_prepare_headers(need_kernel_map, addr, sz, nr_mem_ranges); > + unlock_device_hotplug(); > + > + return ret; > +} > + > /** > * crash_exclude_mem_range - exclude a mem range for existing ranges > * @mem: mem->range contains an array of ranges sorted in ascending order > -- > 2.43.0 >