From f34b6c72c3ebaa286d3311a825ef79eccbcca82f Mon Sep 17 00:00:00 2001 From: "sukadev@linux.vnet.ibm.com" Date: Wed, 10 Dec 2014 14:29:13 -0800 Subject: [PATCH] powerpc/perf/hv-24x7: Use per-cpu page buffer 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 Signed-off-by: Michael Ellerman --- arch/powerpc/perf/hv-24x7.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c index dba34088da28..d073e0679a0c 100644 --- a/arch/powerpc/perf/hv-24x7.c +++ b/arch/powerpc/perf/hv-24x7.c @@ -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; }