linux.git/kernel/events/internal.h, branch v6.6.131

perf/aux: Fix AUX buffer serialization

2024-09-12T09:11:42+00:00

commit 2ab9d830262c132ab5db2f571003d80850d56b2a upstream.

Ole reported that event->mmap_mutex is strictly insufficient to
serialize the AUX buffer, add a per RB mutex to fully serialize it.

Note that in the lock order comment the perf_event::mmap_mutex order
was already wrong, that is, it nesting under mmap_lock is not new with
this patch.

Fixes: 45bfb2e50471 ("perf: Add AUX area to ring buffer for raw data streams")
Reported-by: Ole 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

perf: Fix perf_aux_size() for greater-than 32-bit size

2024-08-03T06:53:41+00:00

[ Upstream commit 3df94a5b1078dfe2b0c03f027d018800faf44c82 ]

perf_buffer->aux_nr_pages uses a 32-bit type, so a cast is needed to
calculate a 64-bit size.

Fixes: 45bfb2e50471 ("perf: Add AUX area to ring buffer for raw data streams")
Signed-off-by: Adrian Hunter 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20240624201101.60186-5-adrian.hunter@intel.com
Signed-off-by: Sasha Levin

perf/core: Fix perf_mmap fail when CONFIG_PERF_USE_VMALLOC enabled

2022-04-19T19:15:42+00:00

This problem can be reproduced with CONFIG_PERF_USE_VMALLOC enabled on
both x86_64 and aarch64 arch when using sysdig -B(using ebpf)[1].
sysdig -B works fine after rebuilding the kernel with
CONFIG_PERF_USE_VMALLOC disabled.

I tracked it down to the if condition event->rb->nr_pages != nr_pages
in perf_mmap is true when CONFIG_PERF_USE_VMALLOC is enabled where
event->rb->nr_pages = 1 and nr_pages = 2048 resulting perf_mmap to
return -EINVAL. This is because when CONFIG_PERF_USE_VMALLOC is
enabled, rb->nr_pages is always equal to 1.

Arch with CONFIG_PERF_USE_VMALLOC enabled by default:
	arc/arm/csky/mips/sh/sparc/xtensa

Arch with CONFIG_PERF_USE_VMALLOC disabled by default:
	x86_64/aarch64/...

Fix this problem by using data_page_nr()

[1] https://github.com/draios/sysdig

Fixes: 906010b2134e ("perf_event: Provide vmalloc() based mmap() backing")
Signed-off-by: Zhipeng Xie 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220209145417.6495-1-xiezhipeng1@huawei.com

tracing/perf: Add interrupt_context_level() helper

2021-10-20T00:33:20+00:00

Now that there are three different instances of doing the addition trick
to the preempt_count() and NMI_MASK, HARDIRQ_MASK and SOFTIRQ_OFFSET
macros, it deserves a helper function defined in the preempt.h header.

Add the interrupt_context_level() helper and replace the three instances
that do that logic with it.

Link: https://lore.kernel.org/all/20211015142541.4badd8a9@gandalf.local.home/

Signed-off-by: Steven Rostedt (VMware)

perf: Optimize get_recursion_context()

2020-11-09T17:12:34+00:00

  "Look ma, no branches!"

Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Jesper Dangaard Brouer 
Link: https://lkml.kernel.org/r/20201030151955.187580298@infradead.org

perf: Fix get_recursion_context()

2020-11-09T17:12:34+00:00

One should use in_serving_softirq() to detect SoftIRQ context.

Fixes: 96f6d4444302 ("perf_counter: avoid recursion")
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20201030151955.120572175@infradead.org

perf/core: Replace zero-length array with flexible-array

2020-05-19T18:34:16+00:00

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20200511201227.GA14041@embeddedor

perf: Make struct ring_buffer less ambiguous

2020-01-13T18:19:38+00:00

eBPF requires needing to know the size of the perf ring buffer structure.
But it unfortunately has the same name as the generic ring buffer used by
tracing and oprofile. To make it less ambiguous, rename the perf ring buffer
structure to "perf_buffer".

As other parts of the ring buffer code has "perf_" as the prefix, it only
makes sense to give the ring buffer the "perf_" prefix as well.

Link: https://lore.kernel.org/r/20191213153553.GE20583@krava
Acked-by: Peter Zijlstra 
Suggested-by: Alexei Starovoitov 
Signed-off-by: Steven Rostedt (VMware)

perf/aux: Allow using AUX data in perf samples

2019-11-13T10:06:14+00:00

AUX data can be used to annotate perf events such as performance counters
or tracepoints/breakpoints by including it in sample records when
PERF_SAMPLE_AUX flag is set. Such samples would be instrumental in debugging
and profiling by providing, for example, a history of instruction flow
leading up to the event's overflow.

The implementation makes use of grouping an AUX event with all the events
that wish to take samples of the AUX data, such that the former is the
group leader. The samplees should also specify the desired size of the AUX
sample via attr.aux_sample_size.

AUX capable PMUs need to explicitly add support for sampling, because it
relies on a new callback to take a snapshot of the buffer without touching
the event states.

Signed-off-by: Alexander Shishkin 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Arnaldo Carvalho de Melo 
Cc: David Ahern 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Mark Rutland 
Cc: Namhyung Kim 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Cc: adrian.hunter@intel.com
Cc: mathieu.poirier@linaro.org
Link: https://lkml.kernel.org/r/20191025140835.53665-2-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar

perf/ring-buffer: Use regular variables for nesting

2019-05-24T07:00:11+00:00

While the IRQ/NMI will nest, the nest-count will be invariant over the
actual exception, since it will decrement equal to increment.

This means we can -- carefully -- use a regular variable since the
typical LOAD-STORE race doesn't exist (similar to preempt_count).

This optimizes the ring-buffer for all LOAD-STORE architectures, since
they need to use atomic ops to implement local_t.

Suggested-by: Alexander Shishkin 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Cc: acme@kernel.org
Cc: mark.rutland@arm.com
Cc: namhyung@kernel.org
Cc: yabinc@google.com
Link: http://lkml.kernel.org/r/20190517115418.481392777@infradead.org
Signed-off-by: Ingo Molnar