From 62bb4cc52695b8d9d57de8133f6cc1d62b1785c4 Mon Sep 17 00:00:00 2001
From: Kaspar Schleiser <kaspar@schleiser.de>
Date: Mon, 28 Jan 2019 17:12:01 +0100
Subject: [PATCH] cpu/native: fix race condition in thread_yield_higher()
Error case:
1. thread_yield_higher() stores the thread's ucontext
2. creates an "isr ucontext" for isr_thread_yield, switches to it
Case 1: no signals are pending, continues in isr_thread_yield()
3a. sched_run is called
4a. return to sched_active_thread ucontext
Case 2: signals pending (the crashing scenario), continues in native_irq_handler()
3b. handles signals
4b. if sched_context_switch_request is set, call sched_run
5b. return to sched_active_thread ucontext
4b misses the call to sched_run(), leading to a possible return into a
non-ready thread.
---
cpu/native/native_cpu.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/cpu/native/native_cpu.c b/cpu/native/native_cpu.c
index 2629e55df0..655562565e 100644
--- a/cpu/native/native_cpu.c
+++ b/cpu/native/native_cpu.c
@@ -208,6 +208,8 @@ void isr_thread_yield(void)
void thread_yield_higher(void)
{
+ sched_context_switch_request = 1;
+
if (_native_in_isr == 0) {
ucontext_t *ctx = (ucontext_t *)(sched_active_thread->sp);
_native_in_isr = 1;
@@ -224,9 +226,6 @@ void thread_yield_higher(void)
}
irq_enable();
}
- else {
- sched_context_switch_request = 1;
- }
}
void native_cpu_init(void)
--
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