linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>,
	x86 <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: [tip: x86/entry] x86/entry: Convert reschedule interrupt to IDTENTRY_SYSVEC_SIMPLE
Date: Wed, 27 May 2020 08:11:47 -0000	[thread overview]
Message-ID: <159056710700.17951.6743495309914679803.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20200521202119.835425642@linutronix.de>

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     064dc9d647c819f4c3196cdd10c06c0770cabf5f
Gitweb:        https://git.kernel.org/tip/064dc9d647c819f4c3196cdd10c06c0770cabf5f
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Thu, 21 May 2020 22:05:45 +02:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 26 May 2020 19:06:29 +02:00

x86/entry: Convert reschedule interrupt to IDTENTRY_SYSVEC_SIMPLE

The scheduler IPI does not need the full interrupt entry handling logic
when the entry is from kernel mode. Use IDTENTRY_SYSVEC_SIMPLE and spare
all the overhead.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202119.835425642@linutronix.de
---
 arch/x86/entry/entry_64.S                |  4 ----
 arch/x86/include/asm/entry_arch.h        |  3 ---
 arch/x86/include/asm/hw_irq.h            |  3 ---
 arch/x86/include/asm/idtentry.h          |  1 +
 arch/x86/include/asm/trace/common.h      |  4 ----
 arch/x86/include/asm/trace/irq_vectors.h | 17 +----------------
 arch/x86/kernel/idt.c                    |  2 +-
 arch/x86/kernel/smp.c                    | 19 ++++---------------
 arch/x86/kernel/tracepoint.c             | 17 -----------------
 9 files changed, 7 insertions(+), 63 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index fd7efb8..9c0722e 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -956,10 +956,6 @@ apicinterrupt3 \num \sym \do_sym
 POP_SECTION_IRQENTRY
 .endm
 
-#ifdef CONFIG_SMP
-apicinterrupt RESCHEDULE_VECTOR			reschedule_interrupt		smp_reschedule_interrupt
-#endif
-
 /*
  * Reload gs selector with exception handling
  * edi:  new selector
diff --git a/arch/x86/include/asm/entry_arch.h b/arch/x86/include/asm/entry_arch.h
index a01bb74..3e841ed 100644
--- a/arch/x86/include/asm/entry_arch.h
+++ b/arch/x86/include/asm/entry_arch.h
@@ -10,6 +10,3 @@
  * is no hardware IRQ pin equivalent for them, they are triggered
  * through the ICC by us (IPIs)
  */
-#ifdef CONFIG_SMP
-BUILD_INTERRUPT(reschedule_interrupt,RESCHEDULE_VECTOR)
-#endif
diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index fd5e7c8..74c1243 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -28,9 +28,6 @@
 #include <asm/irq.h>
 #include <asm/sections.h>
 
-/* Interrupt handlers registered during init_IRQ */
-extern asmlinkage void reschedule_interrupt(void);
-
 #ifdef	CONFIG_X86_LOCAL_APIC
 struct irq_data;
 struct pci_dev;
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index f24701f..d214a30 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -578,6 +578,7 @@ DECLARE_IDTENTRY_SYSVEC(X86_PLATFORM_IPI_VECTOR,	sysvec_x86_platform_ipi);
 #endif
 
 #ifdef CONFIG_SMP
+DECLARE_IDTENTRY(RESCHEDULE_VECTOR,			sysvec_reschedule_ipi);
 DECLARE_IDTENTRY_SYSVEC(IRQ_MOVE_CLEANUP_VECTOR,	sysvec_irq_move_cleanup);
 DECLARE_IDTENTRY_SYSVEC(REBOOT_VECTOR,			sysvec_reboot);
 DECLARE_IDTENTRY_SYSVEC(CALL_FUNCTION_SINGLE_VECTOR,	sysvec_call_function_single);
diff --git a/arch/x86/include/asm/trace/common.h b/arch/x86/include/asm/trace/common.h
index 57c8da0..f0f9bcd 100644
--- a/arch/x86/include/asm/trace/common.h
+++ b/arch/x86/include/asm/trace/common.h
@@ -5,12 +5,8 @@
 DECLARE_STATIC_KEY_FALSE(trace_pagefault_key);
 #define trace_pagefault_enabled()			\
 	static_branch_unlikely(&trace_pagefault_key)
-DECLARE_STATIC_KEY_FALSE(trace_resched_ipi_key);
-#define trace_resched_ipi_enabled()			\
-	static_branch_unlikely(&trace_resched_ipi_key)
 #else
 static inline bool trace_pagefault_enabled(void) { return false; }
-static inline bool trace_resched_ipi_enabled(void) { return false; }
 #endif
 
 #endif
diff --git a/arch/x86/include/asm/trace/irq_vectors.h b/arch/x86/include/asm/trace/irq_vectors.h
index 33b9d0f..88e7f0f 100644
--- a/arch/x86/include/asm/trace/irq_vectors.h
+++ b/arch/x86/include/asm/trace/irq_vectors.h
@@ -10,9 +10,6 @@
 
 #ifdef CONFIG_X86_LOCAL_APIC
 
-extern int trace_resched_ipi_reg(void);
-extern void trace_resched_ipi_unreg(void);
-
 DECLARE_EVENT_CLASS(x86_irq_vector,
 
 	TP_PROTO(int vector),
@@ -37,18 +34,6 @@ DEFINE_EVENT_FN(x86_irq_vector, name##_exit,	\
 	TP_PROTO(int vector),			\
 	TP_ARGS(vector), NULL, NULL);
 
-#define DEFINE_RESCHED_IPI_EVENT(name)		\
-DEFINE_EVENT_FN(x86_irq_vector, name##_entry,	\
-	TP_PROTO(int vector),			\
-	TP_ARGS(vector),			\
-	trace_resched_ipi_reg,			\
-	trace_resched_ipi_unreg);		\
-DEFINE_EVENT_FN(x86_irq_vector, name##_exit,	\
-	TP_PROTO(int vector),			\
-	TP_ARGS(vector),			\
-	trace_resched_ipi_reg,			\
-	trace_resched_ipi_unreg);
-
 /*
  * local_timer - called when entering/exiting a local timer interrupt
  * vector handler
@@ -99,7 +84,7 @@ TRACE_EVENT_PERF_PERM(irq_work_exit, is_sampling_event(p_event) ? -EPERM : 0);
 /*
  * reschedule - called when entering/exiting a reschedule vector handler
  */
-DEFINE_RESCHED_IPI_EVENT(reschedule);
+DEFINE_IRQ_VECTOR_EVENT(reschedule);
 
 /*
  * call_function - called when entering/exiting a call function interrupt
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index faaadd4..bc9b0d1 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -112,7 +112,7 @@ static const __initconst struct idt_data def_idts[] = {
  */
 static const __initconst struct idt_data apic_idts[] = {
 #ifdef CONFIG_SMP
-	INTG(RESCHEDULE_VECTOR,			reschedule_interrupt),
+	INTG(RESCHEDULE_VECTOR,			asm_sysvec_reschedule_ipi),
 	INTG(CALL_FUNCTION_VECTOR,		asm_sysvec_call_function),
 	INTG(CALL_FUNCTION_SINGLE_VECTOR,	asm_sysvec_call_function_single),
 	INTG(IRQ_MOVE_CLEANUP_VECTOR,		asm_sysvec_irq_move_cleanup),
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index e5647da..eff4ce3 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -220,26 +220,15 @@ static void native_stop_other_cpus(int wait)
 
 /*
  * Reschedule call back. KVM uses this interrupt to force a cpu out of
- * guest mode
+ * guest mode.
  */
-__visible void __irq_entry smp_reschedule_interrupt(struct pt_regs *regs)
+DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_reschedule_ipi)
 {
 	ack_APIC_irq();
+	trace_reschedule_entry(RESCHEDULE_VECTOR);
 	inc_irq_stat(irq_resched_count);
-
-	if (trace_resched_ipi_enabled()) {
-		/*
-		 * scheduler_ipi() might call irq_enter() as well, but
-		 * nested calls are fine.
-		 */
-		irq_enter();
-		trace_reschedule_entry(RESCHEDULE_VECTOR);
-		scheduler_ipi();
-		trace_reschedule_exit(RESCHEDULE_VECTOR);
-		irq_exit();
-		return;
-	}
 	scheduler_ipi();
+	trace_reschedule_exit(RESCHEDULE_VECTOR);
 }
 
 DEFINE_IDTENTRY_SYSVEC(sysvec_call_function)
diff --git a/arch/x86/kernel/tracepoint.c b/arch/x86/kernel/tracepoint.c
index 496748e..fcfc077 100644
--- a/arch/x86/kernel/tracepoint.c
+++ b/arch/x86/kernel/tracepoint.c
@@ -25,20 +25,3 @@ void trace_pagefault_unreg(void)
 {
 	static_branch_dec(&trace_pagefault_key);
 }
-
-#ifdef CONFIG_SMP
-
-DEFINE_STATIC_KEY_FALSE(trace_resched_ipi_key);
-
-int trace_resched_ipi_reg(void)
-{
-	static_branch_inc(&trace_resched_ipi_key);
-	return 0;
-}
-
-void trace_resched_ipi_unreg(void)
-{
-	static_branch_dec(&trace_resched_ipi_key);
-}
-
-#endif

  reply	other threads:[~2020-05-27  8:11 UTC|newest]

Thread overview: 132+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21 20:05 [patch V9 00/39] x86/entry: Rework leftovers (was part V) Thomas Gleixner
2020-05-21 20:05 ` [patch V9 01/39] nmi, tracing: Make hardware latency tracing noinstr safe Thomas Gleixner
2020-05-27  8:12   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 02/39] rcu: Abstract out rcu_irq_enter_check_tick() from rcu_nmi_enter() Thomas Gleixner
2020-05-21 21:03   ` Paul E. McKenney
2020-05-21 21:25     ` Thomas Gleixner
2020-05-26  8:14     ` Ingo Molnar
2020-05-26 15:34       ` Paul E. McKenney
2020-05-27  8:12   ` [tip: x86/entry] " tip-bot2 for Paul E. McKenney
2020-05-21 20:05 ` [patch V9 03/39] rcu: Provide rcu_irq_exit_check_preempt() Thomas Gleixner
2020-05-27  8:12   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 04/39] x86/entry: Provide idtentry_entry/exit_cond_rcu() Thomas Gleixner
2020-05-21 21:06   ` Paul E. McKenney
2020-05-26  8:23   ` Ingo Molnar
2020-05-26  8:58     ` Thomas Gleixner
2020-05-21 20:05 ` [patch V9 05/39] x86/entry: Provide idtentry_enter/exit_user() Thomas Gleixner
2020-05-27  8:12   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 06/39] x86/idtentry: Switch to conditional RCU handling Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 07/39] x86/entry: Cleanup idtentry_enter/exit() leftovers Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] x86/entry: Clean up " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 08/39] genirq: Provide irq_enter/exit_rcu() Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 09/39] genirq: Provide __irq_enter/exit_raw() Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 10/39] x86/entry: Provide helpers for execute on irqstack Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] x86/entry: Provide helpers for executing on the irqstack tip-bot2 for Thomas Gleixner
2020-06-05 17:18   ` [patch V9 10/39] x86/entry: Provide helpers for execute on irqstack Qian Cai
2020-06-05 17:36     ` Peter Zijlstra
2020-06-05 17:52       ` Qian Cai
2020-06-07 11:59         ` Thomas Gleixner
2020-06-07 18:27           ` Qian Cai
2020-06-08 16:01       ` Qian Cai
2020-06-08 22:20         ` Thomas Gleixner
2020-06-09  2:32           ` Qian Cai
2020-06-09 20:33             ` Thomas Gleixner
2020-06-09 20:50               ` Thomas Gleixner
2020-06-10 12:38                 ` Qian Cai
2020-06-10 19:38                   ` Thomas Gleixner
2020-06-13 13:55                     ` Qian Cai
2020-06-13 14:03                       ` Thomas Gleixner
2020-06-13 21:41                         ` Qian Cai
2020-06-14  8:59                           ` Thomas Gleixner
2020-05-21 20:05 ` [patch V9 11/39] x86/entry/64: Move do_softirq_own_stack() to C Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 12/39] x86/entry: Split out idtentry_exit_cond_resched() Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 13/39] x86/entry: Switch XEN/PV hypercall entry to IDTENTRY Thomas Gleixner
2020-05-22 18:32   ` [patch V9-1 " Thomas Gleixner
2020-05-26  7:44     ` Jürgen Groß
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 14/39] x86/entry/64: Simplify idtentry_body Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 15/39] x86/entry: Switch page fault exception to IDTENTRY_RAW Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 16/39] x86/entry: Remove the transition leftovers Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 17/39] x86/entry: Change exit path of xen_failsafe_callback Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 18/39] x86/entry/64: Remove error_exit Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] x86/entry/64: Remove error_exit() tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 19/39] x86/entry/32: Remove common_exception Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] x86/entry/32: Remove common_exception() tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 20/39] x86/irq: Use generic irq_regs implementation Thomas Gleixner
2020-05-26 18:39   ` damian
2020-05-28  9:50     ` Thomas Gleixner
2020-05-28 20:20       ` damian
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 21/39] x86/irq: Convey vector as argument and not in ptregs Thomas Gleixner
2020-05-22 19:34   ` Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-08-24 17:29   ` [patch V9 21/39] " Alexander Graf
2020-08-25 10:28     ` Thomas Gleixner
2020-08-25 23:17       ` Alexander Graf
2020-08-25 23:41         ` Andy Lutomirski
2020-08-26  0:04           ` Alexander Graf
2020-08-26  1:03             ` Brian Gerst
2020-08-26  0:55           ` Thomas Gleixner
2020-05-21 20:05 ` [patch V9 22/39] x86/irq: Rework handle_irq() for 64bit Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] x86/irq: Rework handle_irq() for 64-bit tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 23/39] x86/entry: Add IRQENTRY_IRQ macro Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 24/39] x86/entry: Use idtentry for interrupts Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 25/39] x86/entry: Provide IDTENTRY_SYSVEC Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 26/39] x86/entry: Convert APIC interrupts to IDTENTRY_SYSVEC Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 27/39] x86/entry: Convert SMP system vectors " Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 28/39] x86/entry: Convert various system vectors Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 29/39] x86/entry: Convert KVM vectors to IDTENTRY_SYSVEC* Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 30/39] x86/entry: Convert various hypervisor vectors to IDTENTRY_SYSVEC Thomas Gleixner
2020-05-26  9:29   ` Wei Liu
2020-05-27  1:46   ` Boqun Feng
2020-05-27  8:38     ` Wei Liu
2020-05-27 12:09       ` Wei Liu
2020-05-27 23:06         ` Boqun Feng
2020-05-27 12:30       ` Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 31/39] x86/entry: Convert XEN hypercall vector " Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 32/39] x86/entry: Convert reschedule interrupt to IDTENTRY_SYSVEC_SIMPLE Thomas Gleixner
2020-05-27  8:11   ` tip-bot2 for Thomas Gleixner [this message]
2020-05-21 20:05 ` [patch V9 33/39] x86/entry: Remove the apic/BUILD interrupt leftovers Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 34/39] x86/entry/64: Remove IRQ stack switching ASM Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 35/39] x86/entry: Make enter_from_user_mode() static Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 36/39] x86/entry/32: Remove redundant irq disable code Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 37/39] x86/entry/64: Remove TRACE_IRQS_*_DEBUG Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 38/39] x86/entry: Move paranoid irq tracing out of ASM code Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-21 20:05 ` [patch V9 39/39] x86/entry: Remove the TRACE_IRQS cruft Thomas Gleixner
2020-05-27  8:11   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-05-22  7:20 ` [patch V9 00/39] x86/entry: Rework leftovers (was part V) Andrew Cooper
2020-05-22 21:17   ` Peter Zijlstra
2020-06-03 19:18     ` Andrew Cooper
2020-06-04 13:25       ` Peter Zijlstra
2020-06-04 13:29         ` Paolo Bonzini
2020-06-04 13:35           ` Peter Zijlstra
2020-06-04 15:42             ` Andy Lutomirski
2020-06-04 15:55               ` Peter Zijlstra
2020-05-22 14:26 ` Boris Ostrovsky
2020-05-22 17:47   ` Thomas Gleixner
2020-05-22 18:08     ` Thomas Gleixner
2020-05-26  4:33 ` Andy Lutomirski

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=159056710700.17951.6743495309914679803.tip-bot2@tip-bot2 \
    --to=tip-bot2@linutronix.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-tip-commits@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=mingo@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).