[RFC PATCH 5/5] signal: Remove the unnecessary restore_sigmask flag

From: Eric W. Biederman
Date: Fri Jun 07 2019 - 17:48:52 EST


__set_current_blocked already has a test to see if the new
value and the old value of the signal mask differ. Both
real_blocked and blocked should be on the same cache line,
and are a single word compare on 64bit.

Historically real_blocked or saved_sigmask could be garbage
so a test had to be used that always tested valid bits.
Now that real_blocked is alwasy valid there is no need
to test something different.

Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
arch/arc/include/asm/thread_info.h | 1 -
arch/arm/include/asm/thread_info.h | 1 -
arch/arm64/include/asm/thread_info.h | 1 -
arch/c6x/include/asm/thread_info.h | 1 -
arch/csky/include/asm/thread_info.h | 2 -
arch/h8300/include/asm/thread_info.h | 1 -
arch/hexagon/include/asm/thread_info.h | 1 -
arch/m68k/include/asm/thread_info.h | 1 -
arch/mips/include/asm/thread_info.h | 1 -
arch/nds32/include/asm/thread_info.h | 2 -
arch/nios2/include/asm/thread_info.h | 2 -
arch/riscv/include/asm/thread_info.h | 1 -
arch/s390/include/asm/thread_info.h | 1 -
arch/sparc/include/asm/thread_info_32.h | 1 -
arch/um/include/asm/thread_info.h | 1 -
arch/unicore32/include/asm/thread_info.h | 1 -
arch/xtensa/include/asm/thread_info.h | 1 -
include/linux/sched.h | 3 -
include/linux/sched/signal.h | 79 +-----------------------
kernel/ptrace.c | 2 -
kernel/signal.c | 7 ---
21 files changed, 1 insertion(+), 110 deletions(-)

diff --git a/arch/arc/include/asm/thread_info.h b/arch/arc/include/asm/thread_info.h
index c85947bac5e5..bde0f76a986b 100644
--- a/arch/arc/include/asm/thread_info.h
+++ b/arch/arc/include/asm/thread_info.h
@@ -77,7 +77,6 @@ static inline __attribute_const__ struct thread_info *current_thread_info(void)
* - pending work-to-be-done flags are in LSW
* - other flags in MSW
*/
-#define TIF_RESTORE_SIGMASK 0 /* restore sig mask in do_signal() */
#define TIF_NOTIFY_RESUME 1 /* resumption notification requested */
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 286eb61c632b..d1ee97031c21 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -147,7 +147,6 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
#define TIF_NOHZ 12 /* in adaptive nohz mode */
#define TIF_USING_IWMMXT 17
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
-#define TIF_RESTORE_SIGMASK 20

#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index eb3ef73e07cf..bb8fdc9f78d2 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -93,7 +93,6 @@ void arch_release_task_struct(struct task_struct *tsk);
#define TIF_SECCOMP 11
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
#define TIF_FREEZE 19
-#define TIF_RESTORE_SIGMASK 20
#define TIF_SINGLESTEP 21
#define TIF_32BIT 22 /* 32bit process */
#define TIF_SVE 23 /* Scalable Vector Extension in use */
diff --git a/arch/c6x/include/asm/thread_info.h b/arch/c6x/include/asm/thread_info.h
index 59a5697fe0f3..229d365ffa9d 100644
--- a/arch/c6x/include/asm/thread_info.h
+++ b/arch/c6x/include/asm/thread_info.h
@@ -84,7 +84,6 @@ struct thread_info *current_thread_info(void)
#define TIF_NOTIFY_RESUME 1 /* resumption notification requested */
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
-#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */

#define TIF_MEMDIE 17 /* OOM killer killed process */

diff --git a/arch/csky/include/asm/thread_info.h b/arch/csky/include/asm/thread_info.h
index 0b546a55a8bf..f7261865e9dc 100644
--- a/arch/csky/include/asm/thread_info.h
+++ b/arch/csky/include/asm/thread_info.h
@@ -59,7 +59,6 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_SYSCALL_AUDIT 5 /* syscall auditing */
#define TIF_POLLING_NRFLAG 16 /* poll_idle() is TIF_NEED_RESCHED */
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
-#define TIF_RESTORE_SIGMASK 20 /* restore signal mask in do_signal() */
#define TIF_SECCOMP 21 /* secure computing */

#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
@@ -70,7 +69,6 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_MEMDIE (1 << TIF_MEMDIE)
-#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)

#endif /* _ASM_CSKY_THREAD_INFO_H */
diff --git a/arch/h8300/include/asm/thread_info.h b/arch/h8300/include/asm/thread_info.h
index 0cdaa302d3d2..8d5d5063628a 100644
--- a/arch/h8300/include/asm/thread_info.h
+++ b/arch/h8300/include/asm/thread_info.h
@@ -68,7 +68,6 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
#define TIF_SINGLESTEP 3 /* singlestepping active */
#define TIF_MEMDIE 4 /* is terminating due to OOM killer */
-#define TIF_RESTORE_SIGMASK 5 /* restore signal mask in do_signal() */
#define TIF_NOTIFY_RESUME 6 /* callback before returning to user */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SYSCALL_TRACEPOINT 8 /* for ftrace syscall instrumentation */
diff --git a/arch/hexagon/include/asm/thread_info.h b/arch/hexagon/include/asm/thread_info.h
index f41f9c6f0e31..2d1183690bc5 100644
--- a/arch/hexagon/include/asm/thread_info.h
+++ b/arch/hexagon/include/asm/thread_info.h
@@ -107,7 +107,6 @@ register struct thread_info *__current_thread_info asm(QUOTED_THREADINFO_REG);
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_SINGLESTEP 4 /* restore ss @ return to usr mode */
-#define TIF_RESTORE_SIGMASK 6 /* restore sig mask in do_signal() */
/* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17 /* OOM killer killed process */

diff --git a/arch/m68k/include/asm/thread_info.h b/arch/m68k/include/asm/thread_info.h
index 015f1ca38305..d620cb4f240e 100644
--- a/arch/m68k/include/asm/thread_info.h
+++ b/arch/m68k/include/asm/thread_info.h
@@ -66,6 +66,5 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_DELAYED_TRACE 14 /* single step a syscall */
#define TIF_SYSCALL_TRACE 15 /* syscall trace active */
#define TIF_MEMDIE 16 /* is terminating due to OOM killer */
-#define TIF_RESTORE_SIGMASK 18 /* restore signal mask in do_signal */

#endif /* _ASM_M68K_THREAD_INFO_H */
diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h
index 4993db40482c..b2327b51c141 100644
--- a/arch/mips/include/asm/thread_info.h
+++ b/arch/mips/include/asm/thread_info.h
@@ -97,7 +97,6 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_SECCOMP 4 /* secure computing */
#define TIF_NOTIFY_RESUME 5 /* callback before returning to user */
#define TIF_UPROBE 6 /* breakpointed or singlestepping */
-#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal() */
#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
#define TIF_NOHZ 19 /* in adaptive nohz mode */
diff --git a/arch/nds32/include/asm/thread_info.h b/arch/nds32/include/asm/thread_info.h
index c135111ec44e..79914ce56cd9 100644
--- a/arch/nds32/include/asm/thread_info.h
+++ b/arch/nds32/include/asm/thread_info.h
@@ -52,7 +52,6 @@ struct thread_info {
#define TIF_POLLING_NRFLAG 17
#define TIF_MEMDIE 18
#define TIF_FREEZE 19
-#define TIF_RESTORE_SIGMASK 20

#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
@@ -61,7 +60,6 @@ struct thread_info {
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_FREEZE (1 << TIF_FREEZE)
-#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)

/*
* Change these and you break ASM code in entry-common.S
diff --git a/arch/nios2/include/asm/thread_info.h b/arch/nios2/include/asm/thread_info.h
index 7349a4fa635b..b17309c3a5b3 100644
--- a/arch/nios2/include/asm/thread_info.h
+++ b/arch/nios2/include/asm/thread_info.h
@@ -86,7 +86,6 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_MEMDIE 4 /* is terminating due to OOM killer */
#define TIF_SECCOMP 5 /* secure computing */
#define TIF_SYSCALL_AUDIT 6 /* syscall auditing active */
-#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal() */

#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling
TIF_NEED_RESCHED */
@@ -97,7 +96,6 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
-#define _TIF_RESTORE_SIGMASK (1 << TIF_RESTORE_SIGMASK)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)

/* work to do on interrupt/exception return */
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index 9c039870019b..6a1e393b4b5f 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -79,7 +79,6 @@ struct thread_info {
#define TIF_NOTIFY_RESUME 1 /* callback before returning to user */
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
-#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */
#define TIF_MEMDIE 5 /* is terminating due to OOM killer */
#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing */
diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h
index ce4e17c9aad6..6a1d1636016b 100644
--- a/arch/s390/include/asm/thread_info.h
+++ b/arch/s390/include/asm/thread_info.h
@@ -71,7 +71,6 @@ void arch_setup_new_exec(void);

#define TIF_31BIT 16 /* 32bit process */
#define TIF_MEMDIE 17 /* is terminating due to OOM killer */
-#define TIF_RESTORE_SIGMASK 18 /* restore signal mask in do_signal() */
#define TIF_SINGLE_STEP 19 /* This task is single stepped */
#define TIF_BLOCK_STEP 20 /* This task is block stepped */
#define TIF_UPROBE_SINGLESTEP 21 /* This task is uprobe single stepped */
diff --git a/arch/sparc/include/asm/thread_info_32.h b/arch/sparc/include/asm/thread_info_32.h
index 548b366165dd..567f472c730b 100644
--- a/arch/sparc/include/asm/thread_info_32.h
+++ b/arch/sparc/include/asm/thread_info_32.h
@@ -103,7 +103,6 @@ register struct thread_info *current_thread_info_reg asm("g6");
#define TIF_NOTIFY_RESUME 1 /* callback before returning to user */
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
-#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */
#define TIF_USEDFPU 8 /* FPU was used by this task
* this quantum (SMP) */
#define TIF_POLLING_NRFLAG 9 /* true if poll_idle() is polling
diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h
index 4eecd960ee8c..565b7db73083 100644
--- a/arch/um/include/asm/thread_info.h
+++ b/arch/um/include/asm/thread_info.h
@@ -60,7 +60,6 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_RESTART_BLOCK 4
#define TIF_MEMDIE 5 /* is terminating due to OOM killer */
#define TIF_SYSCALL_AUDIT 6
-#define TIF_RESTORE_SIGMASK 7
#define TIF_NOTIFY_RESUME 8
#define TIF_SECCOMP 9 /* secure computing */

diff --git a/arch/unicore32/include/asm/thread_info.h b/arch/unicore32/include/asm/thread_info.h
index 5fb728f3b49a..0f38f6072839 100644
--- a/arch/unicore32/include/asm/thread_info.h
+++ b/arch/unicore32/include/asm/thread_info.h
@@ -119,7 +119,6 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
#define TIF_SYSCALL_TRACE 8
#define TIF_MEMDIE 18
-#define TIF_RESTORE_SIGMASK 20

#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
diff --git a/arch/xtensa/include/asm/thread_info.h b/arch/xtensa/include/asm/thread_info.h
index f092cc3f4e66..27350241615c 100644
--- a/arch/xtensa/include/asm/thread_info.h
+++ b/arch/xtensa/include/asm/thread_info.h
@@ -108,7 +108,6 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_SINGLESTEP 3 /* restore singlestep on return to user mode */
#define TIF_SYSCALL_TRACEPOINT 4 /* syscall tracepoint instrumentation */
#define TIF_MEMDIE 5 /* is terminating due to OOM killer */
-#define TIF_RESTORE_SIGMASK 6 /* restore signal mask in do_signal() */
#define TIF_NOTIFY_RESUME 7 /* callback before returning to user */
#define TIF_DB_DISABLED 8 /* debug trap disabled for syscall */

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 520efbd355be..a5284f5ccb7c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -713,9 +713,6 @@ struct task_struct {
/* Bit to tell LSMs we're in execve(): */
unsigned in_execve:1;
unsigned in_iowait:1;
-#ifndef TIF_RESTORE_SIGMASK
- unsigned restore_sigmask:1;
-#endif
#ifdef CONFIG_MEMCG
unsigned in_user_fault:1;
#endif
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 78678de45278..ac34566e762f 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -400,86 +400,9 @@ static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)

void task_join_group_stop(struct task_struct *task);

-#ifdef TIF_RESTORE_SIGMASK
-/*
- * Legacy restore_sigmask accessors. These are inefficient on
- * SMP architectures because they require atomic operations.
- */
-
-/**
- * set_restore_sigmask() - make sure real_sigmask processing gets done
- *
- * This sets TIF_RESTORE_SIGMASK and ensures that the arch signal code
- * will run before returning to user mode, to process the flag. For
- * all callers, TIF_SIGPENDING is already set or it's no harm to set
- * it. TIF_RESTORE_SIGMASK need not be in the set of bits that the
- * arch code will notice on return to user mode, in case those bits
- * are scarce. We set TIF_SIGPENDING here to ensure that the arch
- * signal code always gets run when TIF_RESTORE_SIGMASK is set.
- */
-static inline void set_restore_sigmask(void)
-{
- set_thread_flag(TIF_RESTORE_SIGMASK);
-}
-
-static inline void clear_tsk_restore_sigmask(struct task_struct *task)
-{
- clear_tsk_thread_flag(task, TIF_RESTORE_SIGMASK);
-}
-
-static inline void clear_restore_sigmask(void)
-{
- clear_thread_flag(TIF_RESTORE_SIGMASK);
-}
-static inline bool test_tsk_restore_sigmask(struct task_struct *task)
-{
- return test_tsk_thread_flag(task, TIF_RESTORE_SIGMASK);
-}
-static inline bool test_restore_sigmask(void)
-{
- return test_thread_flag(TIF_RESTORE_SIGMASK);
-}
-static inline bool test_and_clear_restore_sigmask(void)
-{
- return test_and_clear_thread_flag(TIF_RESTORE_SIGMASK);
-}
-
-#else /* TIF_RESTORE_SIGMASK */
-
-/* Higher-quality implementation, used if TIF_RESTORE_SIGMASK doesn't exist. */
-static inline void set_restore_sigmask(void)
-{
- current->restore_sigmask = true;
-}
-static inline void clear_tsk_restore_sigmask(struct task_struct *task)
-{
- task->restore_sigmask = false;
-}
-static inline void clear_restore_sigmask(void)
-{
- current->restore_sigmask = false;
-}
-static inline bool test_restore_sigmask(void)
-{
- return current->restore_sigmask;
-}
-static inline bool test_tsk_restore_sigmask(struct task_struct *task)
-{
- return task->restore_sigmask;
-}
-static inline bool test_and_clear_restore_sigmask(void)
-{
- if (!current->restore_sigmask)
- return false;
- current->restore_sigmask = false;
- return true;
-}
-#endif
-
static inline void restore_saved_sigmask(void)
{
- if (test_and_clear_restore_sigmask())
- __set_current_blocked(&current->real_blocked);
+ __set_current_blocked(&current->real_blocked);
}

extern int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize);
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 5ed6126e1cc5..08e25bbb04f4 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -963,8 +963,6 @@ int ptrace_request(struct task_struct *child, long request,
child->real_blocked = new_set;
spin_unlock_irq(&child->sighand->siglock);

- clear_tsk_restore_sigmask(child);
-
ret = 0;
break;
}
diff --git a/kernel/signal.c b/kernel/signal.c
index c37d4f209699..1358e6bf02d3 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2734,12 +2734,6 @@ static void signal_delivered(struct ksignal *ksig, int stepping)
{
sigset_t blocked;

- /* A signal was successfully delivered, and the
- saved sigmask was stored on the signal frame,
- and will be restored by sigreturn. So we can
- simply clear the restore sigmask flag. */
- clear_restore_sigmask();
-
sigorsets(&blocked, &current->blocked, &ksig->ka.sa.sa_mask);
if (!(ksig->ka.sa.sa_flags & SA_NODEFER))
sigaddset(&blocked, ksig->sig);
@@ -2940,7 +2934,6 @@ EXPORT_SYMBOL(sigprocmask);

static int set_sigmask(sigset_t *newset)
{
- set_restore_sigmask();
sigdelsetmask(newset, sigmask(SIGKILL) | sigmask(SIGSTOP));
__set_current_blocked(newset);

--
2.21.0.dirty