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authorDavid Miller <davem@davemloft.net>2020-02-24 15:01:53 +0100
committerAlexei Starovoitov <ast@kernel.org>2020-02-24 16:20:10 -0800
commit099bfaa731ec347d3f16a463ae53b88a1700c0af (patch)
tree38d6b44dc8654900cfb0e735cd8d027ce00d4e53 /kernel/bpf/stackmap.c
parent66150d0dde030c5ee68ccd93e4c54a73c47ebebd (diff)
bpf/stackmap: Dont trylock mmap_sem with PREEMPT_RT and interrupts disabled
In a RT kernel down_read_trylock() cannot be used from NMI context and up_read_non_owner() is another problematic issue. So in such a configuration, simply elide the annotated stackmap and just report the raw IPs. In the longer term, it might be possible to provide a atomic friendly versions of the page cache traversal which will at least provide the info if the pages are resident and don't need to be paged in. [ tglx: Use IS_ENABLED() to avoid the #ifdeffery, fixup the irq work callback and add a comment ] Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200224145644.708960317@linutronix.de
Diffstat (limited to 'kernel/bpf/stackmap.c')
-rw-r--r--kernel/bpf/stackmap.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 3f958b90d914..db76339fe358 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -40,6 +40,9 @@ static void do_up_read(struct irq_work *entry)
{
struct stack_map_irq_work *work;
+ if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
+ return;
+
work = container_of(entry, struct stack_map_irq_work, irq_work);
up_read_non_owner(work->sem);
work->sem = NULL;
@@ -288,10 +291,19 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
struct stack_map_irq_work *work = NULL;
if (irqs_disabled()) {
- work = this_cpu_ptr(&up_read_work);
- if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY)
- /* cannot queue more up_read, fallback */
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ work = this_cpu_ptr(&up_read_work);
+ if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY) {
+ /* cannot queue more up_read, fallback */
+ irq_work_busy = true;
+ }
+ } else {
+ /*
+ * PREEMPT_RT does not allow to trylock mmap sem in
+ * interrupt disabled context. Force the fallback code.
+ */
irq_work_busy = true;
+ }
}
/*