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BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86869fe8 of 8 bytes by interrupt on cpu 0:
 data_alloc+0x310/0x390 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x964/0xb60 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x610 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 buffer_io_error fs/buffer.c:130 [inline]
 end_buffer_async_read fs/buffer.c:271 [inline]
 end_buffer_async_read_io+0x232/0x250 fs/buffer.c:380
 end_bio_bh_io_sync+0x79/0xa0 fs/buffer.c:2776
 bio_endio+0x37e/0x420 block/bio.c:1671
 blk_update_request+0x336/0x730 block/blk-mq.c:1007
 blk_mq_end_request+0x26/0x50 block/blk-mq.c:1169
 lo_complete_rq+0x98/0x140 drivers/block/loop.c:314
 blk_complete_reqs block/blk-mq.c:1244 [inline]
 blk_done_softirq+0x77/0xb0 block/blk-mq.c:1249
 handle_softirqs+0xba/0x290 kernel/softirq.c:622
 run_ksoftirqd+0x1c/0x30 kernel/softirq.c:1063
 smpboot_thread_fn+0x32b/0x530 kernel/smpboot.c:160
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffffffff86869fe8 of 16 bytes by task 2991 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1bc/0x920 kernel/printk/printk_ringbuffer.c:2170
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 syslog_print+0x23a/0x540 kernel/printk/printk.c:1626
 do_syslog+0x52b/0x7e0 kernel/printk/printk.c:1761
 __do_sys_syslog kernel/printk/printk.c:1853 [inline]
 __se_sys_syslog kernel/printk/printk.c:1851 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1851
 x64_sys_call+0x27ce/0x3000 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2991 Comm: klogd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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