linux-kernel - [PATCH v2 04/10] um: Turn signals

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Message-Id: <20250810055136.897712-5-tiwei.bie@linux.dev>
Date: Sun, 10 Aug 2025 13:51:30 +0800
From: Tiwei Bie <tiwei.bie@...ux.dev>
To: richard@....at,
	anton.ivanov@...bridgegreys.com,
	johannes@...solutions.net
Cc: linux-um@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	benjamin@...solutions.net,
	arnd@...db.de,
	tiwei.btw@...group.com,
	tiwei.bie@...ux.dev
Subject: [PATCH v2 04/10] um: Turn signals_* into thread-local variables

From: Tiwei Bie <tiwei.btw@...group.com>

Turn signals_enabled, signals_pending and signals_active into
thread-local variables. This enables us to control and track
signals independently on each CPU thread. This is a preparation
for adding SMP support.

Signed-off-by: Tiwei Bie <tiwei.btw@...group.com>
---
 arch/um/include/asm/irqflags.h   |  4 ++--
 arch/um/include/shared/longjmp.h |  3 +--
 arch/um/include/shared/os.h      |  1 +
 arch/um/kernel/ksyms.c           |  2 +-
 arch/um/os-Linux/signal.c        | 11 ++++++++---
 5 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/um/include/asm/irqflags.h b/arch/um/include/asm/irqflags.h
index 1e69ef5bc35e..31e49e0894c5 100644
--- a/arch/um/include/asm/irqflags.h
+++ b/arch/um/include/asm/irqflags.h
@@ -2,7 +2,7 @@
 #ifndef __UM_IRQFLAGS_H
 #define __UM_IRQFLAGS_H
 
-extern int signals_enabled;
+int um_get_signals(void);
 int um_set_signals(int enable);
 void block_signals(void);
 void unblock_signals(void);
@@ -10,7 +10,7 @@ void unblock_signals(void);
 #define arch_local_save_flags arch_local_save_flags
 static inline unsigned long arch_local_save_flags(void)
 {
-	return signals_enabled;
+	return um_get_signals();
 }
 
 #define arch_local_irq_restore arch_local_irq_restore
diff --git a/arch/um/include/shared/longjmp.h b/arch/um/include/shared/longjmp.h
index 8863319039f3..c53e43d980c8 100644
--- a/arch/um/include/shared/longjmp.h
+++ b/arch/um/include/shared/longjmp.h
@@ -5,7 +5,6 @@
 #include <sysdep/archsetjmp.h>
 #include <os.h>
 
-extern int signals_enabled;
 extern int setjmp(jmp_buf);
 extern void longjmp(jmp_buf, int);
 
@@ -15,7 +14,7 @@ extern void longjmp(jmp_buf, int);
 
 #define UML_SETJMP(buf) ({				\
 	int n, enable;					\
-	enable = *(volatile int *)&signals_enabled;	\
+	enable = um_get_signals();			\
 	n = setjmp(*buf);				\
 	if(n != 0)					\
 		um_set_signals_trace(enable);		\
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index b35cc8ce333b..324d4eed3385 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -243,6 +243,7 @@ extern void send_sigio_to_self(void);
 extern int change_sig(int signal, int on);
 extern void block_signals(void);
 extern void unblock_signals(void);
+extern int um_get_signals(void);
 extern int um_set_signals(int enable);
 extern int um_set_signals_trace(int enable);
 extern void deliver_alarm(void);
diff --git a/arch/um/kernel/ksyms.c b/arch/um/kernel/ksyms.c
index f2fb77da08cf..96314c31e61c 100644
--- a/arch/um/kernel/ksyms.c
+++ b/arch/um/kernel/ksyms.c
@@ -6,8 +6,8 @@
 #include <linux/module.h>
 #include <os.h>
 
+EXPORT_SYMBOL(um_get_signals);
 EXPORT_SYMBOL(um_set_signals);
-EXPORT_SYMBOL(signals_enabled);
 
 EXPORT_SYMBOL(os_stat_fd);
 EXPORT_SYMBOL(os_stat_file);
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 11f07f498270..58da8c6ece98 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -68,12 +68,12 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 #define SIGCHLD_BIT 2
 #define SIGCHLD_MASK (1 << SIGCHLD_BIT)
 
-int signals_enabled;
+static __thread int signals_enabled;
 #if IS_ENABLED(CONFIG_UML_TIME_TRAVEL_SUPPORT)
 static int signals_blocked, signals_blocked_pending;
 #endif
-static unsigned int signals_pending;
-static unsigned int signals_active = 0;
+static __thread unsigned int signals_pending;
+static __thread unsigned int signals_active;
 
 static void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
 {
@@ -342,6 +342,11 @@ void unblock_signals(void)
 	}
 }
 
+int um_get_signals(void)
+{
+	return signals_enabled;
+}
+
 int um_set_signals(int enable)
 {
 	int ret;
-- 
2.34.1