diff options
| author | David Miller <davem@davemloft.net> | 2020-02-24 15:01:53 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-02-25 01:20:10 +0100 |
| commit | 099bfaa731ec347d3f16a463ae53b88a1700c0af (patch) | |
| tree | 38d6b44dc8654900cfb0e735cd8d027ce00d4e53 /kernel/bpf/stackmap.c | |
| parent | bpf, lpm: Make locking RT friendly (diff) | |
| download | linux-099bfaa731ec347d3f16a463ae53b88a1700c0af.tar.xz linux-099bfaa731ec347d3f16a463ae53b88a1700c0af.zip | |
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.c | 18 |
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; + } } /* |