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Paul Burton b81b3e959a tracing: Simplify & fix saved_tgids logic
The tgid_map array records a mapping from pid to tgid, where the index
of an entry within the array is the pid & the value stored at that index
is the tgid.

The saved_tgids_next() function iterates over pointers into the tgid_map
array & dereferences the pointers which results in the tgid, but then it
passes that dereferenced value to trace_find_tgid() which treats it as a
pid & does a further lookup within the tgid_map array. It seems likely
that the intent here was to skip over entries in tgid_map for which the
recorded tgid is zero, but instead we end up skipping over entries for
which the thread group leader hasn't yet had its own tgid recorded in
tgid_map.

A minimal fix would be to remove the call to trace_find_tgid, turning:

  if (trace_find_tgid(*ptr))

into:

  if (*ptr)

..but it seems like this logic can be much simpler if we simply let
seq_read() iterate over the whole tgid_map array & filter out empty
entries by returning SEQ_SKIP from saved_tgids_show(). Here we take that
approach, removing the incorrect logic here entirely.

Link: https://lkml.kernel.org/r/20210630003406.4013668-1-paulburton@google.com

Fixes: d914ba37d7 ("tracing: Add support for recording tgid of tasks")
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Paul Burton <paulburton@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2021-06-30 09:19:14 -04:00
arch trace/osnoise: Fix 'no previous prototype' warnings 2021-06-28 14:12:26 -04:00
block block-5.13-2021-05-22 2021-05-22 07:40:34 -10:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto for-5.13/drivers-2021-04-27 2021-04-28 14:39:37 -07:00
Documentation Documentation: Fix a typo on trace/osnoise-tracer 2021-06-28 14:12:27 -04:00
drivers treewide: Add missing semicolons to __assign_str uses 2021-06-30 09:19:14 -04:00
fs treewide: Add missing semicolons to __assign_str uses 2021-06-30 09:19:14 -04:00
include treewide: Add missing semicolons to __assign_str uses 2021-06-30 09:19:14 -04:00
init bootconfig: Share the checksum function with tools 2021-06-10 13:41:26 -04:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-22 15:09:07 -10:00
kernel tracing: Simplify & fix saved_tgids logic 2021-06-30 09:19:14 -04:00
lib seq_buf: Make trace_seq_putmem_hex() support data longer than 8 2021-06-26 09:19:16 -04:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm, hugetlb: fix simple resv_huge_pages underflow on UFFDIO_COPY 2021-06-05 08:58:12 -07:00
net Networking fixes for 5.13-rc5, including fixes from bpf, wireless, 2021-06-04 18:25:39 -07:00
samples VFIO fixes for v5.13-rc5 2021-06-03 11:52:24 -07:00
scripts kbuild: Quote OBJCOPY var to avoid a pahole call break the build 2021-05-27 11:32:56 -07:00
security trusted-keys: match tpm_get_ops on all return paths 2021-05-12 22:36:37 +03:00
sound sound fixes for 5.13-rc5 2021-06-04 10:13:20 -07:00
tools bootconfig/tracing/ktest: Add ktest examples of testing bootconfig 2021-06-24 15:34:33 -04:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: VMX: update vcpu posted-interrupt descriptor when assigning device 2021-05-27 07:58:23 -04:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: use private address for Michel Lespinasse 2021-06-05 08:58:12 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
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 Networking fixes for 5.13-rc5, including fixes from bpf, wireless, 2021-06-04 18:25:39 -07:00
Makefile Linux 5.13-rc5 2021-06-06 15:47:27 -07:00
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.