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powerpc/perf/hv-24x7: Use per-cpu page buffer

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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>
This commit is contained in:
sukadev@linux.vnet.ibm.com 2014-12-10 14:29:13 -08:00 committed by Michael Ellerman
parent b123429e6a
commit f34b6c72c3
1 changed files with 9 additions and 12 deletions
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21
arch/powerpc/perf/hv-24x7.c
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@ -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;
}