[PATCH v4 14/14] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores
From: Will Deacon <will@kernel.org>
Date: 2020-11-24 15:52:33
Also in:
linux-arch, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
The scheduler now knows enough about these braindead systems to place 32-bit tasks accordingly, so throw out the safety checks and allow the ret-to-user path to avoid do_notify_resume() if there is nothing to do. Signed-off-by: Will Deacon <will@kernel.org> --- arch/arm64/kernel/process.c | 14 +------------- arch/arm64/kernel/signal.c | 26 -------------------------- 2 files changed, 1 insertion(+), 39 deletions(-)
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 72116b0c7c73..e21c631c8b17 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c@@ -543,15 +543,6 @@ static void erratum_1418040_thread_switch(struct task_struct *prev, write_sysreg(val, cntkctl_el1); } -static void compat_thread_switch(struct task_struct *next) -{ - if (!is_compat_thread(task_thread_info(next))) - return; - - if (static_branch_unlikely(&arm64_mismatched_32bit_el0)) - set_tsk_thread_flag(next, TIF_NOTIFY_RESUME); -} - /* * Thread switching. */
@@ -568,7 +559,6 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, uao_thread_switch(next); ssbs_thread_switch(next); erratum_1418040_thread_switch(prev, next); - compat_thread_switch(next); /* * Complete any pending TLB or cache maintenance on this CPU in case
@@ -644,7 +634,7 @@ static void adjust_compat_task_affinity(struct task_struct *p) * execve(). */ if (!restrict_cpus_allowed_ptr(p, possible_mask)) - goto out; + return; if (alloc_cpumask_var(&cpuset_mask, GFP_KERNEL)) { cpuset_cpus_allowed(p, cpuset_mask);
@@ -661,8 +651,6 @@ static void adjust_compat_task_affinity(struct task_struct *p) out_set_mask: set_cpus_allowed_ptr(p, newmask); free_cpumask_var(cpuset_mask); -out: - set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); } /*
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index bcb6ca2d9a7c..a8184cad8890 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c@@ -911,19 +911,6 @@ static void do_signal(struct pt_regs *regs) restore_saved_sigmask(); } -static bool cpu_affinity_invalid(struct pt_regs *regs) -{ - if (!compat_user_mode(regs)) - return false; - - /* - * We're preemptible, but a reschedule will cause us to check the - * affinity again. - */ - return !cpumask_test_cpu(raw_smp_processor_id(), - system_32bit_el0_cpumask()); -} - asmlinkage void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags) {
@@ -961,19 +948,6 @@ asmlinkage void do_notify_resume(struct pt_regs *regs, if (thread_flags & _TIF_NOTIFY_RESUME) { tracehook_notify_resume(regs); rseq_handle_notify_resume(NULL, regs); - - /* - * If we reschedule after checking the affinity - * then we must ensure that TIF_NOTIFY_RESUME - * is set so that we check the affinity again. - * Since tracehook_notify_resume() clears the - * flag, ensure that the compiler doesn't move - * it after the affinity check. - */ - barrier(); - - if (cpu_affinity_invalid(regs)) - force_sig(SIGKILL); } if (thread_flags & _TIF_FOREIGN_FPSTATE)
--
2.29.2.454.gaff20da3a2-goog
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