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Subject[PATCH v2 0/7] tracing: Kill the buggy trace_cpu
Hello.

This series kills tracing_open_generic_tc/trace_cpu/etc.

trace_array_get(inode->i_private) is mostly fine, we do not
dereference this pointer untill trace_array_get() succeeds.
But trace_array_get(tc->tr) is wrong by the same reason why
tracing_open_generic_file/etc are wrong, see 1/7.

(Steven, I think you are right and we can also remove the
list_for_each_entry() loop from trace_array_get() later,
and avoid the (harmless but still) race with rmdir + mkdir.
Lets discuss this after we fix the problems with file/call).

Changes:

1/7: Fix the whitespace problems.

Add the comment above tracing_get_cpu() and update
the changelog. tracing_get_cpu() is always safe but
the code like

cpu = tracing_get_cpu(inode);
if (trace_array_get(tr) == 0)
do_something(tr, cpu);

is racy, it can wrongly use RING_BUFFER_ALL_CPUS.
IOW, tracing_get_cpu() should be used only after
trace_array_get() or something else which takes
trace_types_lock at least once.

5/7: No changes. checkpatch.pl complains, but that
"line over 80 characters" in tracing_entries_read()
was not added by this patch and I do not know how
can I make checkpatch.pl happy without adding a
helper for per_cpu_ptr(tr->trace_buffer.data).

6/7: Incorporated the fix from Steven (thanks!).

Oleg.

kernel/trace/trace.c | 194 +++++++++++++++++++++-----------------------------
kernel/trace/trace.h | 8 --
2 files changed, 80 insertions(+), 122 deletions(-)



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