powerpc/perf/hv-24x7: Use per-cpu page buffer (f34b6c72) · Commits · 戴 / test

The 24x7 counters are continuously running and not updated on an interrupt. So we record the event counts when stopping the event or deleting it. But to "read" a single counter in 24x7, we allocate a page and pass it into the hypervisor (The HV returns the page full of counters from which we extract the specific counter for this event). We allocate a page using GFP_USER and when deleting the event, we end up with the following warning because we are blocking in interrupt context. [ 698.641709] BUG: scheduling while atomic: swapper/0/0/0x10010000 We could use GFP_ATOMIC but that could result in failures. Pre-allocate a buffer so we don't have to allocate in interrupt context. Further as Michael Ellerman suggested, use Per-CPU buffer so we only need to allocate once per CPU. Cc: stable@vger.kernel.org Signed-off-by:

Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/perf/hv-24x7.c

+9 −12

Original line number	Diff line number	Diff line
		@@ -217,11 +217,14 @@ static bool is_physical_domain(int domain)
		domain == HV_24X7_PERF_DOMAIN_PHYSICAL_CORE;
		}

		DEFINE_PER_CPU(char, hv_24x7_reqb[4096]) __aligned(4096);
		DEFINE_PER_CPU(char, hv_24x7_resb[4096]) __aligned(4096);

		static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
		u16 lpar, u64 *res,
		bool success_expected)
		{
		unsigned long ret = -ENOMEM;
		unsigned long ret;

		/*
		* request_buffer and result_buffer are not required to be 4k aligned,
		@@ -243,13 +246,11 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
		BUILD_BUG_ON(sizeof(*request_buffer) > 4096);
		BUILD_BUG_ON(sizeof(*result_buffer) > 4096);

		request_buffer = kmem_cache_zalloc(hv_page_cache, GFP_USER);
		if (!request_buffer)
		goto out;
		request_buffer = (void *)get_cpu_var(hv_24x7_reqb);
		result_buffer = (void *)get_cpu_var(hv_24x7_resb);

		result_buffer = kmem_cache_zalloc(hv_page_cache, GFP_USER);
		if (!result_buffer)
		goto out_free_request_buffer;
		memset(request_buffer, 0, 4096);
		memset(result_buffer, 0, 4096);

		*request_buffer = (struct reqb) {
		.buf = {
		@@ -278,15 +279,11 @@ static unsigned long single_24x7_request(u8 domain, u32 offset, u16 ix,
		domain, offset, ix, lpar, ret, ret,
		result_buffer->buf.detailed_rc,
		result_buffer->buf.failing_request_ix);
		goto out_free_result_buffer;
		goto out;
		}

		*res = be64_to_cpu(result_buffer->result);

		out_free_result_buffer:
		kfree(result_buffer);
		out_free_request_buffer:
		kfree(request_buffer);
		out:
		return ret;
		}

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