Re: [PATCH v2 2/2] tracing: Remove trace_printk.h from kernel.h
From: Yury Norov <yury.norov@gmail.com>
Date: 2026-06-22 16:01:08
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On Mon, Jun 22, 2026 at 09:07:41AM -0400, Steven Rostedt wrote:
From: Steven Rostedt <rostedt@goodmis.org> There have been complaints about trace_printk.h causing more build time for being in kernel.h. Move it out of kernel.h and place it in the headers and C files that use it. Link: https://lore.kernel.org/all/CAHk-=wikCBeVFjVXiY4o-oepdbjAoir5+TcAgtL12c4u1TpZLQ@mail.gmail.com/ (local)
Link is nice, but can you explain in the commit message what those complaints exactly are? There's enough opinions shared to make a nice summary. I even think it's important enough to become a Documentation rule.
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Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- Changes since v1: https://patch.msgid.link/20260621093811.168514984@kernel.org - Just remove trace_printk.h and fix up all the places that need it. arch/powerpc/kvm/book3s_xics.c | 1 + drivers/gpu/drm/i915/gt/intel_gtt.h | 1 + drivers/gpu/drm/i915/i915_gem.h | 1 + drivers/hwtracing/stm/dummy_stm.c | 4 ++++ drivers/infiniband/hw/hfi1/trace_dbg.h | 1 + drivers/usb/early/xhci-dbc.c | 1 + fs/ext4/inline.c | 1 + include/linux/ftrace.h | 2 ++ include/linux/kernel.h | 1 - include/linux/sunrpc/debug.h | 1 + include/linux/trace_printk.h | 5 +++-- kernel/trace/ring_buffer_benchmark.c | 1 + samples/fprobe/fprobe_example.c | 1 + samples/ftrace/ftrace-direct-too.c | 1 - samples/trace_printk/trace-printk.c | 1 + 15 files changed, 19 insertions(+), 4 deletions(-)diff --git a/arch/powerpc/kvm/book3s_xics.c b/arch/powerpc/kvm/book3s_xics.c index 74a44fa702b0..ef5eb596a56e 100644 --- a/arch/powerpc/kvm/book3s_xics.c +++ b/arch/powerpc/kvm/book3s_xics.c@@ -26,6 +26,7 @@ #if 1 #define XICS_DBG(fmt...) do { } while (0) #else +#include <linux/trace_printk.h> #define XICS_DBG(fmt...) trace_printk(fmt) #endifdiff --git a/drivers/gpu/drm/i915/gt/intel_gtt.h b/drivers/gpu/drm/i915/gt/intel_gtt.h index b54ee4f25af1..f6f223090760 100644 --- a/drivers/gpu/drm/i915/gt/intel_gtt.h +++ b/drivers/gpu/drm/i915/gt/intel_gtt.h@@ -35,6 +35,7 @@ #define I915_GFP_ALLOW_FAIL (GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN) #if IS_ENABLED(CONFIG_DRM_I915_TRACE_GTT) +#include <linux/trace_printk.h>
So, before it was included unconditionally, now it's included. It looks technically correct, but conceptually - I'm not sure. I'm not a developer of this driver, but ... here we need trace_printk.h if TRACE_GTT is enabled, in the next header TRACE_GEM needs it. To me it sounds like the whole driver simply needs trace_printk.h.
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#define GTT_TRACE(...) trace_printk(__VA_ARGS__) #else #define GTT_TRACE(...)diff --git a/drivers/gpu/drm/i915/i915_gem.h b/drivers/gpu/drm/i915/i915_gem.h index 1da8fb61c09e..f490052e8964 100644 --- a/drivers/gpu/drm/i915/i915_gem.h +++ b/drivers/gpu/drm/i915/i915_gem.h@@ -117,6 +117,7 @@ int i915_gem_open(struct drm_i915_private *i915, struct drm_file *file); #if IS_ENABLED(CONFIG_DRM_I915_TRACE_GEM) #include <linux/trace_controls.h> +#include <linux/trace_printk.h> #define GEM_TRACE(...) trace_printk(__VA_ARGS__) #define GEM_TRACE_ERR(...) do { \ pr_err(__VA_ARGS__); \diff --git a/drivers/hwtracing/stm/dummy_stm.c b/drivers/hwtracing/stm/dummy_stm.c index 38528ffdc0b3..784f9af7ccba 100644 --- a/drivers/hwtracing/stm/dummy_stm.c +++ b/drivers/hwtracing/stm/dummy_stm.c@@ -14,6 +14,10 @@ #include <linux/stm.h> #include <uapi/linux/stm.h> +#ifdef DEBUG +#include <linux/trace_printk.h> +#endif +
Same here. The cost of adding the header in a particular C file is unmeasurable. But playing "#undef DEBUG #ifdef DEBUG" games looks weird. Imagine, the developer has this DEBUG enabled, then adds another debugging trace_pritnk() out of the DEBUG block, compiles his patch well, then sends to the user, who has DEBUG disabled; and now we hit the same problem as in the config-based case. Let's put it simple: dummy_stm just needs trace_printk.h.
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static ssize_t notrace dummy_stm_packet(struct stm_data *stm_data, unsigned int master, unsigned int channel, unsigned int packet, unsigned int flags,diff --git a/drivers/infiniband/hw/hfi1/trace_dbg.h b/drivers/infiniband/hw/hfi1/trace_dbg.h index 58304b91380f..30df5e246586 100644 --- a/drivers/infiniband/hw/hfi1/trace_dbg.h +++ b/drivers/infiniband/hw/hfi1/trace_dbg.h@@ -103,6 +103,7 @@ __hfi1_trace_def(IOCTL); */ #ifdef HFI1_EARLY_DBG +#include <linux/trace_printk.h> #define hfi1_dbg_early(fmt, ...) \ trace_printk(fmt, ##__VA_ARGS__) #elsediff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c index 41118bba9197..955c73bd601f 100644 --- a/drivers/usb/early/xhci-dbc.c +++ b/drivers/usb/early/xhci-dbc.c@@ -30,6 +30,7 @@ static struct xdbc_state xdbc; static bool early_console_keep; #ifdef XDBC_TRACE +#include <linux/trace_printk.h> #define xdbc_trace trace_printk #else static inline void xdbc_trace(const char *fmt, ...) { }diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c index 8045e4ff270c..0eff4a0c6a6c 100644 --- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c@@ -934,6 +934,7 @@ static int ext4_da_convert_inline_data_to_extent(struct address_space *mapping, } #ifdef INLINE_DIR_DEBUG +#include <linux/trace_printk.h> void ext4_show_inline_dir(struct inode *dir, struct buffer_head *bh, void *inline_start, int inline_size) {diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 02bc5027523a..b5336a81e619 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h@@ -8,6 +8,8 @@ #define _LINUX_FTRACE_H #include <linux/trace_recursion.h> +#include <linux/trace_controls.h> +#include <linux/trace_printk.h> #include <linux/trace_clock.h> #include <linux/jump_label.h> #include <linux/kallsyms.h>diff --git a/include/linux/kernel.h b/include/linux/kernel.h index e5570a16cbb1..e87a40fbd152 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h@@ -31,7 +31,6 @@ #include <linux/build_bug.h> #include <linux/sprintf.h> #include <linux/static_call_types.h> -#include <linux/trace_printk.h> #include <linux/util_macros.h> #include <linux/wordpart.h>diff --git a/include/linux/sunrpc/debug.h b/include/linux/sunrpc/debug.h index ab61bed2f7af..7524f5d82fba 100644 --- a/include/linux/sunrpc/debug.h +++ b/include/linux/sunrpc/debug.h@@ -29,6 +29,7 @@ extern unsigned int nlm_debug; # define ifdebug(fac) if (unlikely(rpc_debug & RPCDBG_##fac)) # if IS_ENABLED(CONFIG_SUNRPC_DEBUG_TRACE) +# include <linux/trace_printk.h> # define __sunrpc_printk(fmt, ...) trace_printk(fmt, ##__VA_ARGS__) # else # define __sunrpc_printk(fmt, ...) printk(KERN_DEFAULT fmt, ##__VA_ARGS__)diff --git a/include/linux/trace_printk.h b/include/linux/trace_printk.h index a488ea9e9f85..74ce4f8995c4 100644 --- a/include/linux/trace_printk.h +++ b/include/linux/trace_printk.h@@ -1,11 +1,12 @@ /* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_TRACE_PRINTK_H #define _LINUX_TRACE_PRINTK_H +#if !defined(__ASSEMBLY__) && !defined(__GENKSYMS__) && !defined(BUILD_VDSO) -#include <linux/compiler_attributes.h> #include <linux/instruction_pointer.h> #include <linux/stddef.h> #include <linux/stringify.h> +#include <linux/stdarg.h> #ifdef CONFIG_TRACING static inline __printf(1, 2)@@ -147,5 +148,5 @@ ftrace_vprintk(const char *fmt, va_list ap) return 0; } #endif /* CONFIG_TRACING */ - +#endif /* !defined(__ASSEMBLY__) && !defined(__GENKSYMS__) && !defined(BUILD_VDSO) */ #endifdiff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c index 593e3b59e42e..2bb25caebb75 100644 --- a/kernel/trace/ring_buffer_benchmark.c +++ b/kernel/trace/ring_buffer_benchmark.c@@ -5,6 +5,7 @@ * Copyright (C) 2009 Steven Rostedt <srostedt@redhat.com> */ #include <linux/ring_buffer.h> +#include <linux/trace_printk.h> #include <linux/completion.h> #include <linux/kthread.h> #include <uapi/linux/sched/types.h>diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c index bfe98ce826f3..de81b9b4ca7d 100644 --- a/samples/fprobe/fprobe_example.c +++ b/samples/fprobe/fprobe_example.c@@ -12,6 +12,7 @@ #define pr_fmt(fmt) "%s: " fmt, __func__ +#include <linux/trace_printk.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/fprobe.h>diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c index bf2411aa6fd7..159190f4103f 100644 --- a/samples/ftrace/ftrace-direct-too.c +++ b/samples/ftrace/ftrace-direct-too.c@@ -1,6 +1,5 @@ // SPDX-License-Identifier: GPL-2.0-only #include <linux/module.h> - #include <linux/mm.h> /* for handle_mm_fault() */ #include <linux/ftrace.h> #if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)diff --git a/samples/trace_printk/trace-printk.c b/samples/trace_printk/trace-printk.c index cfc159580263..ff37aeb8523e 100644 --- a/samples/trace_printk/trace-printk.c +++ b/samples/trace_printk/trace-printk.c@@ -1,4 +1,5 @@ // SPDX-License-Identifier: GPL-2.0-only +#include <linux/trace_printk.h> #include <linux/module.h> #include <linux/kthread.h> #include <linux/irq_work.h>-- 2.53.0