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Jin Yao c4735d9902 perf evsel: Don't set sample_regs_intr/sample_regs_user for dummy event 
Since commit 0a892c1c94 ("perf record: Add dummy event during system wide synthesis"),
a dummy event is added to capture mmaps.

But if we run perf-record as,

 # perf record -e cycles:p -IXMM0 -a -- sleep 1
 Error:
 dummy:HG: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat'

The issue is, if we enable the extended regs (-IXMM0), but the
pmu->capabilities is not set with PERF_PMU_CAP_EXTENDED_REGS, the kernel
will return -EOPNOTSUPP error.

See following code:

/* in kernel/events/core.c */
static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)

{
        ....
        if (!(pmu->capabilities & PERF_PMU_CAP_EXTENDED_REGS) &&
            has_extended_regs(event))
                ret = -EOPNOTSUPP;
        ....
}

For software dummy event, the PMU should not be set with
PERF_PMU_CAP_EXTENDED_REGS. But unfortunately now, the dummy
event has possibility to be set with PERF_REG_EXTENDED_MASK bit.

In evsel__config, /* tools/perf/util/evsel.c */

if (opts->sample_intr_regs) {
        attr->sample_regs_intr = opts->sample_intr_regs;
}

If we use -IXMM0, the attr>sample_regs_intr will be set with
PERF_REG_EXTENDED_MASK bit.

It doesn't make sense to set attr->sample_regs_intr for a
software dummy event.

This patch adds dummy event checking before setting
attr->sample_regs_intr and attr->sample_regs_user.

After:
  # ./perf record -e cycles:p -IXMM0 -a -- sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.413 MB perf.data (45 samples) ]

Committer notes:

Adrian said this when providing his Acked-by:

"
This is fine.  It will not break PT.

no_aux_samples is useful for evsels that have been added by the code rather
than requested by the user.  For old kernels PT adds sched_switch tracepoint
to track context switches (before the current context switch event was
added) and having auxiliary sample information unnecessarily uses up space
in the perf buffer.
"

Fixes: 0a892c1c94 ("perf record: Add dummy event during system wide synthesis")
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200720010013.18238-1-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-08-04 09:04:31 -03:00
arch A single fix for a potential deadlock when printing a message about spurious interrupts. 2020-08-02 13:10:42 -07:00
block block-5.8-2020-07-10 2020-07-10 09:55:46 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto keys: asymmetric: fix error return code in software_key_query() 2020-07-15 15:49:04 -07:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-01 16:47:24 -07:00
drivers Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-01 16:47:24 -07:00
fs io_uring-5.8-2020-07-30 2020-07-30 09:47:07 -07:00
include Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-01 16:47:24 -07:00
init kbuild: fix CONFIG_CC_CAN_LINK(_STATIC) for cross-compilation with Clang 2020-07-02 00:57:45 +09:00
ipc mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-01 16:47:24 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-01 16:47:24 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm khugepaged: fix null-pointer dereference due to race 2020-07-24 12:42:41 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-01 16:47:24 -07:00
samples samples/vfs: avoid warning in statx override 2020-07-03 16:15:25 -07:00
scripts kbuild: remove redundant FORCE definition in scripts/Makefile.modpost 2020-08-02 23:09:16 +09:00
security integrity/ima: switch to using __kernel_read 2020-07-08 08:27:57 +02:00
sound sound fixes for 5.8-final or -rc8 2020-07-31 09:17:24 -07:00
tools perf evsel: Don't set sample_regs_intr/sample_regs_user for dummy event 2020-08-04 09:04:31 -03:00
usr bpfilter: match bit size of bpfilter_umh to that of the kernel 2020-05-17 18:52:01 +09:00
virt kvm: use more precise cast and do not drop __user 2020-07-02 05:39:31 -04:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Do not track defconfig from make savedefconfig 2020-07-05 16:15:46 +09:00
.mailmap mailmap: add entry for Mike Rapoport 2020-07-24 12:42:41 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS mailmap: change email for Ricardo Ribalda 2020-05-25 18:59:59 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-01 16:47:24 -07:00
Makefile Linux 5.8 2020-08-02 14:21:45 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.