mm/percpu.c: fix panic triggered by BUG_ON() falsely (8f606604) · Commits · 戴 / test

As shown by pcpu_build_alloc_info(), the number of units within a percpu group is deduced by rounding up the number of CPUs within the group to @upa boundary/ Therefore, the number of CPUs isn't equal to the units's if it isn't aligned to @upa normally. However, pcpu_page_first_chunk() uses BUG_ON() to assert that one number is equal to the other roughly, so a panic is maybe triggered by the BUG_ON() incorrectly. In order to fix this issue, the number of CPUs is rounded up then compared with units's and the BUG_ON() is replaced with a warning and return of an error code as well, to keep system alive as much as possible. Link: http://lkml.kernel.org/r/57FCF07C.2020103@zoho.com Signed-off-by:

zijun_hu <zijun_hu@htc.com> Cc: Tejun Heo <tj@kernel.org> Cc: Christoph Lameter <cl@linux.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/percpu.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -2093,6 +2093,8 @@ int __init pcpu_page_first_chunk(size_t reserved_size,
		size_t pages_size;
		struct page **pages;
		int unit, i, j, rc;
		int upa;
		int nr_g0_units;

		snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);

		@@ -2100,7 +2102,12 @@ int __init pcpu_page_first_chunk(size_t reserved_size,
		if (IS_ERR(ai))
		return PTR_ERR(ai);
		BUG_ON(ai->nr_groups != 1);
		BUG_ON(ai->groups[0].nr_units != num_possible_cpus());
		upa = ai->alloc_size/ai->unit_size;
		nr_g0_units = roundup(num_possible_cpus(), upa);
		if (unlikely(WARN_ON(ai->groups[0].nr_units != nr_g0_units))) {
		pcpu_free_alloc_info(ai);
		return -EINVAL;
		}

		unit_pages = ai->unit_size >> PAGE_SHIFT;

		@@ -2111,9 +2118,9 @@ int __init pcpu_page_first_chunk(size_t reserved_size,

		/* allocate pages */
		j = 0;
		for (unit = 0; unit < num_possible_cpus(); unit++)
		for (i = 0; i < unit_pages; i++) {
		for (unit = 0; unit < num_possible_cpus(); unit++) {
		unsigned int cpu = ai->groups[0].cpu_map[unit];
		for (i = 0; i < unit_pages; i++) {
		void *ptr;

		ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
		@@ -2126,6 +2133,7 @@ int __init pcpu_page_first_chunk(size_t reserved_size,
		kmemleak_free(ptr);
		pages[j++] = virt_to_page(ptr);
		}
		}

		/* allocate vm area, map the pages and copy static data */
		vm.flags = VM_ALLOC;

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