tracing: Remove TRACE_FLAG_IRQS_NOSUPPORT

It was possible to enable tracing with no IRQ tracing support. The
tracing infrastructure would then record TRACE_FLAG_IRQS_NOSUPPORT as
the only tracing flag and show an 'X' in the output.

The last user of this feature was PPC32 which managed to implement it
during PowerPC merge in 2009. Since then, it was unused and the PPC32
dependency was finally removed in commit 0ea5ee0 ("tracing: Remove
PPC32 wart from config TRACING_SUPPORT").
Since the PowerPC merge the code behind !CONFIG_TRACE_IRQFLAGS_SUPPORT
with TRACING enabled can no longer be selected used and the 'X' is not
displayed or recorded.

Remove the CONFIG_TRACE_IRQFLAGS_SUPPORT from the tracing code. Remove
TRACE_FLAG_IRQS_NOSUPPORT.

Cc: Peter Zijlstra <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: Sebastian Andrzej Siewior

Documentation/trace/ftrace.rst

@@ -1031,9 +1031,6 @@ explains which is which.
   CPU#: The CPU which the process was running on.
 
   irqs-off: 'd' interrupts are disabled. '.' otherwise.
-	.. caution:: If the architecture does not support a way to
-		read the irq flags variable, an 'X' will always
-		be printed here.
 
   need-resched:
 	- 'N' both TIF_NEED_RESCHED and PREEMPT_NEED_RESCHED is set,

include/linux/trace_events.h

@@ -184,7 +184,6 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status);
 
 enum trace_flag_type {
 	TRACE_FLAG_IRQS_OFF		= 0x01,
-	TRACE_FLAG_IRQS_NOSUPPORT	= 0x02,
 	TRACE_FLAG_NEED_RESCHED		= 0x04,
 	TRACE_FLAG_HARDIRQ		= 0x08,
 	TRACE_FLAG_SOFTIRQ		= 0x10,
@@ -193,7 +192,6 @@ enum trace_flag_type {
 	TRACE_FLAG_BH_OFF		= 0x80,
 };
 
-#ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
 static inline unsigned int tracing_gen_ctx_flags(unsigned long irqflags)
 {
 	unsigned int irq_status = irqs_disabled_flags(irqflags) ?
@@ -207,17 +205,6 @@ static inline unsigned int tracing_gen_ctx(void)
 	local_save_flags(irqflags);
 	return tracing_gen_ctx_flags(irqflags);
 }
-#else
-
-static inline unsigned int tracing_gen_ctx_flags(unsigned long irqflags)
-{
-	return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT);
-}
-static inline unsigned int tracing_gen_ctx(void)
-{
-	return tracing_gen_ctx_irq_test(TRACE_FLAG_IRQS_NOSUPPORT);
-}
-#endif
 
 static inline unsigned int tracing_gen_ctx_dec(void)
 {

kernel/trace/trace_output.c

@@ -460,7 +460,6 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
 		(entry->flags & TRACE_FLAG_IRQS_OFF && bh_off) ? 'D' :
 		(entry->flags & TRACE_FLAG_IRQS_OFF) ? 'd' :
 		bh_off ? 'b' :
-		(entry->flags & TRACE_FLAG_IRQS_NOSUPPORT) ? 'X' :
 		'.';
 
 	switch (entry->flags & (TRACE_FLAG_NEED_RESCHED |