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authorChris Metcalf <cmetcalf@mellanox.com>2016-07-14 23:48:14 +0300
committerWill Deacon <will.deacon@arm.com>2016-08-22 12:00:48 +0300
commit421dd6fa6709ebee4f888ed89da5c103c77caee1 (patch)
tree2ee670bc18f5fbe691906340c0a54b42f7f2635a /arch/arm64/kernel/signal.c
parent0a7d87a7776e2616334473c4209e277b6ca300e5 (diff)
downloadlinux-421dd6fa6709ebee4f888ed89da5c103c77caee1.tar.xz
arm64: factor work_pending state machine to C
Currently ret_fast_syscall, work_pending, and ret_to_user form an ad-hoc state machine that can be difficult to reason about due to duplicated code and a large number of branch targets. This patch factors the common logic out into the existing do_notify_resume function, converting the code to C in the process, making the code more legible. This patch tries to closely mirror the existing behaviour while using the usual C control flow primitives. As local_irq_{disable,enable} may be instrumented, we balance exception entry (where we will almost most likely enable IRQs) with a call to trace_hardirqs_on just before the return to userspace. Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/signal.c')
-rw-r--r--arch/arm64/kernel/signal.c36
1 files changed, 26 insertions, 10 deletions
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index a8eafdbc7cb8..404dd67080b9 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -402,15 +402,31 @@ static void do_signal(struct pt_regs *regs)
asmlinkage void do_notify_resume(struct pt_regs *regs,
unsigned int thread_flags)
{
- if (thread_flags & _TIF_SIGPENDING)
- do_signal(regs);
-
- if (thread_flags & _TIF_NOTIFY_RESUME) {
- clear_thread_flag(TIF_NOTIFY_RESUME);
- tracehook_notify_resume(regs);
- }
-
- if (thread_flags & _TIF_FOREIGN_FPSTATE)
- fpsimd_restore_current_state();
+ /*
+ * The assembly code enters us with IRQs off, but it hasn't
+ * informed the tracing code of that for efficiency reasons.
+ * Update the trace code with the current status.
+ */
+ trace_hardirqs_off();
+ do {
+ if (thread_flags & _TIF_NEED_RESCHED) {
+ schedule();
+ } else {
+ local_irq_enable();
+
+ if (thread_flags & _TIF_SIGPENDING)
+ do_signal(regs);
+
+ if (thread_flags & _TIF_NOTIFY_RESUME) {
+ clear_thread_flag(TIF_NOTIFY_RESUME);
+ tracehook_notify_resume(regs);
+ }
+
+ if (thread_flags & _TIF_FOREIGN_FPSTATE)
+ fpsimd_restore_current_state();
+ }
+ local_irq_disable();
+ thread_flags = READ_ONCE(current_thread_info()->flags);
+ } while (thread_flags & _TIF_WORK_MASK);
}