linux-toradex.git/include/linux/tracepoint.h, branch v5.12-rc7

tracepoints: Code clean up

2021-02-09T17:27:29+00:00

Restructure the code a bit to make it simpler, fix some formatting problems
and add READ_ONCE/WRITE_ONCE to make sure there's no compiler load/store
tearing to the variables that can be accessed across CPUs.

Started with Mathieu Desnoyers's patch:

  Link: https://lore.kernel.org/lkml/20210203175741.20665-1-mathieu.desnoyers@efficios.com/

And will keep his signature, but I will take the responsibility of this
being correct, and keep the authorship.

Link: https://lkml.kernel.org/r/20210204143004.61126582@gandalf.local.home

Signed-off-by: Mathieu Desnoyers 
Signed-off-by: Steven Rostedt (VMware)

tracepoints: Do not punish non static call users

2021-02-09T17:16:27+00:00

With static calls, a tracepoint can call the callback directly if there is
only one callback registered to that tracepoint. When there is more than
one, the static call will call the tracepoint's "iterator" function, which
needs to reload the tracepoint's "funcs" array again, as it could have
changed since the first time it was loaded.

But an arch without static calls is punished by having to load the
tracepoint's "funcs" array twice. Once in the DO_TRACE macro, and once
again in the iterator macro.

For archs without static calls, there's no reason to load the array macro
in the first place, since the iterator function will do it anyway.

Change the __DO_TRACE_CALL() macro to do the load and call of the
tracepoints funcs array only for architectures with static calls, and just
call the iterator function directly for architectures without static calls.

Link: https://lkml.kernel.org/r/20210208201050.909329787@goodmis.org

Acked-by: Peter Zijlstra (Intel) 
Signed-off-by: Steven Rostedt (VMware)

tracepoints: Remove unnecessary "data_args" macro parameter

2021-02-09T17:16:27+00:00

While working on a clean up that would restructure the difference between
architectures that have static calls vs those that do not, I was stumbling
over the "data_args" parameter that includes "__data" in the arguments. The
issue was that one version didn't even need it, while the other one did.
Instead of injecting a "__data = NULL;" into the macro for the unneeded
version, just remove it completely.

The original idea behind data_args is that there may be a case of a
tracepoint with no arguments. But this is considered bad practice, and all
tracepoints should pass something to that location (that's what tracepoints
were created for).

Link: https://lkml.kernel.org/r/20210208201050.768074128@goodmis.org

Acked-by: Peter Zijlstra (Intel) 
Signed-off-by: Steven Rostedt (VMware)

tracepoint: Fix race between tracing and removing tracepoint

2021-02-02T14:32:02+00:00

When executing a tracepoint, the tracepoint's func is dereferenced twice -
in __DO_TRACE() (where the returned pointer is checked) and later on in
__traceiter_##_name where the returned pointer is dereferenced without
checking which leads to races against tracepoint_removal_sync() and
crashes.

This adds a check before referencing the pointer in tracepoint_ptr_deref.

Link: https://lkml.kernel.org/r/20210202072326.120557-1-aik@ozlabs.ru

Cc: stable@vger.kernel.org
Fixes: d25e37d89dd2f ("tracepoint: Optimize using static_call()")
Acked-by: Peter Zijlstra (Intel) 
Signed-off-by: Alexey Kardashevskiy 
Signed-off-by: Steven Rostedt (VMware)

treewide: Convert macro and uses of section(foo) to section("foo")

2020-10-25T21:51:49+00:00

Use a more generic form for __section that requires quotes to avoid
complications with clang and gcc differences.

Remove the quote operator # from compiler_attributes.h __section macro.

Convert all unquoted __section(foo) uses to quoted __section("foo").
Also convert __attribute__((section("foo"))) uses to __section("foo")
even if the __attribute__ has multiple list entry forms.

Conversion done using the script at:

    https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.pl

Signed-off-by: Joe Perches 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Miguel Ojeda 
Signed-off-by: Linus Torvalds

tracepoint: Fix overly long tracepoint names

2020-09-08T12:10:59+00:00

Stephen Rothwell reported:

> Exported symbols need to be <= (64 - sizeof(Elf_Addr)) long.  This is
> presumably 56 on 64 bit arches and the above symbol (including the '.')
> is 56 characters long.

Shorten the tracepoint symbol name.

Fixes: d25e37d89dd2 ("tracepoint: Optimize using static_call()")
Reported-by: Stephen Rothwell 
Signed-off-by: Peter Zijlstra 
Signed-off-by: Ingo Molnar 
Link: https://lore.kernel.org/r/20200908105743.GW2674@hirez.programming.kicks-ass.net

tracepoint: Optimize using static_call()

2020-09-01T07:58:06+00:00

Currently the tracepoint site will iterate a vector and issue indirect
calls to however many handlers are registered (ie. the vector is
long).

Using static_call() it is possible to optimize this for the common
case of only having a single handler registered. In this case the
static_call() can directly call this handler. Otherwise, if the vector
is longer than 1, call a function that iterates the whole vector like
the current code.

[peterz: updated to new interface]

Signed-off-by: Steven Rostedt (VMware) 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/r/20200818135805.279421092@infradead.org

tracepoint: Use __used attribute definitions from compiler_attributes.h

2020-08-03T17:34:37+00:00

Just a small cleanup while I was touching this header.
compiler_attributes.h does feature detection of these __attributes__(())
and provides more concise ways to invoke them.

Link: https://lkml.kernel.org/r/20200730224555.2142154-3-ndesaulniers@google.com

Acked-by: Miguel Ojeda 
Signed-off-by: Nick Desaulniers 
Signed-off-by: Steven Rostedt (VMware)

tracepoint: Mark __tracepoint_string's __used

2020-08-03T17:34:04+00:00

__tracepoint_string's have their string data stored in .rodata, and an
address to that data stored in the "__tracepoint_str" section. Functions
that refer to those strings refer to the symbol of the address. Compiler
optimization can replace those address references with references
directly to the string data. If the address doesn't appear to have other
uses, then it appears dead to the compiler and is removed. This can
break the /tracing/printk_formats sysfs node which iterates the
addresses stored in the "__tracepoint_str" section.

Like other strings stored in custom sections in this header, mark these
__used to inform the compiler that there are other non-obvious users of
the address, so they should still be emitted.

Link: https://lkml.kernel.org/r/20200730224555.2142154-2-ndesaulniers@google.com

Cc: Ingo Molnar 
Cc: Miguel Ojeda 
Cc: stable@vger.kernel.org
Fixes: 102c9323c35a8 ("tracing: Add __tracepoint_string() to export string pointers")
Reported-by: Tim Murray 
Reported-by: Simon MacMullen 
Suggested-by: Greg Hackmann 
Signed-off-by: Nick Desaulniers 
Signed-off-by: Steven Rostedt (VMware)

tracing: Remove DECLARE_TRACE_NOARGS

2020-04-23T02:06:35+00:00

This macro was intentionally broken so that the kernel code is not
poluted with such noargs macro used simply as markers. This use case
can be satisfied by using dummy no inline functions. Just remove it.

Link: http://lkml.kernel.org/r/20200413153246.8511-1-nborisov@suse.com

Signed-off-by: Nikolay Borisov 
Signed-off-by: Steven Rostedt (VMware)