Merge: bpf: Use raw_spinlock_t in ringbuf

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/5593

JIRA: https://issues.redhat.com/browse/RHEL-20608

commit 8b62645\
Author: Wander Lairson Costa wander.lairson@gmail.com\
Date: Fri Sep 20 16:06:59 2024 -0300

```
bpf: Use raw_spinlock_t in ringbuf  

The function __bpf_ringbuf_reserve is invoked from a tracepoint, which  
disables preemption. Using spinlock_t in this context can lead to a  
"sleep in atomic" warning in the RT variant. This issue is illustrated  
in the example below:  

BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48  
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 556208, name: test_progs  
preempt_count: 1, expected: 0  
RCU nest depth: 1, expected: 1  
INFO: lockdep is turned off.  
Preemption disabled at:  
[<ffffd33a5c88ea44>] migrate_enable+0xc0/0x39c  
CPU: 7 PID: 556208 Comm: test_progs Tainted: G  
Hardware name: Qualcomm SA8775P Ride (DT)  
Call trace:  
 dump_backtrace+0xac/0x130  
 show_stack+0x1c/0x30  
 dump_stack_lvl+0xac/0xe8  
 dump_stack+0x18/0x30  
 __might_resched+0x3bc/0x4fc  
 rt_spin_lock+0x8c/0x1a4  
 __bpf_ringbuf_reserve+0xc4/0x254  
 bpf_ringbuf_reserve_dynptr+0x5c/0xdc  
 bpf_prog_ac3d15160d62622a_test_read_write+0x104/0x238  
 trace_call_bpf+0x238/0x774  
 perf_call_bpf_enter.isra.0+0x104/0x194  
 perf_syscall_enter+0x2f8/0x510  
 trace_sys_enter+0x39c/0x564  
 syscall_trace_enter+0x220/0x3c0  
 do_el0_svc+0x138/0x1dc  
 el0_svc+0x54/0x130  
 el0t_64_sync_handler+0x134/0x150  
 el0t_64_sync+0x17c/0x180  

Switch the spinlock to raw_spinlock_t to avoid this error.  

Fixes: 457f443 ("bpf: Implement BPF ring buffer and verifier support for it")  
Reported-by: Brian Grech <bgrech@redhat.com>  
Signed-off-by: Wander Lairson Costa <wander.lairson@gmail.com>  
Signed-off-by: Wander Lairson Costa <wander@redhat.com>  
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>  
Acked-by: Daniel Borkmann <daniel@iogearbox.net>  
Link: https://lore.kernel.org/r/20240920190700.617253-1-wander@redhat.com  
```

Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>

Approved-by: Derek Barbosa <debarbos@redhat.com>
Approved-by: Juri Lelli <juri.lelli@redhat.com>
Approved-by: Valentin Schneider <vschneid@redhat.com>
Approved-by: Viktor Malik <vmalik@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Rado Vrbovsky <rvrbovsk@redhat.com>

Author: emmil

kernel/bpf/ringbuf.c

@@ -29,7 +29,7 @@ struct bpf_ringbuf {
 	u64 mask;
 	struct page **pages;
 	int nr_pages;
-	spinlock_t spinlock ____cacheline_aligned_in_smp;
+	raw_spinlock_t spinlock ____cacheline_aligned_in_smp;
 	/* For user-space producer ring buffers, an atomic_t busy bit is used
 	 * to synchronize access to the ring buffers in the kernel, rather than
 	 * the spinlock that is used for kernel-producer ring buffers. This is
@@ -173,7 +173,7 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
 	if (!rb)
 		return NULL;
 
-	spin_lock_init(&rb->spinlock);
+	raw_spin_lock_init(&rb->spinlock);
 	atomic_set(&rb->busy, 0);
 	init_waitqueue_head(&rb->waitq);
 	init_irq_work(&rb->work, bpf_ringbuf_notify);
@@ -421,10 +421,10 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
 	cons_pos = smp_load_acquire(&rb->consumer_pos);
 
 	if (in_nmi()) {
-		if (!spin_trylock_irqsave(&rb->spinlock, flags))
+		if (!raw_spin_trylock_irqsave(&rb->spinlock, flags))
 			return NULL;
 	} else {
-		spin_lock_irqsave(&rb->spinlock, flags);
+		raw_spin_lock_irqsave(&rb->spinlock, flags);
 	}
 
 	pend_pos = rb->pending_pos;
@@ -450,7 +450,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
 	 */
 	if (new_prod_pos - cons_pos > rb->mask ||
 	    new_prod_pos - pend_pos > rb->mask) {
-		spin_unlock_irqrestore(&rb->spinlock, flags);
+		raw_spin_unlock_irqrestore(&rb->spinlock, flags);
 		return NULL;
 	}
 
@@ -462,7 +462,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
 	/* pairs with consumer's smp_load_acquire() */
 	smp_store_release(&rb->producer_pos, new_prod_pos);
 
-	spin_unlock_irqrestore(&rb->spinlock, flags);
+	raw_spin_unlock_irqrestore(&rb->spinlock, flags);
 
 	return (void *)hdr + BPF_RINGBUF_HDR_SZ;
 }