[SRU][J/N:linux-bluefield][PATCH v1 0/1] ipmb_host: lock warning in ipmb_slave_cb

[David Thompson]

BugLink: https://bugs.launchpad.net/bugs/2127673

SRU Justification:

[Impact]
Booting BF3 with kernel that has lock-related debug enabled
will result in the following warning:

[ 21.758110] 1 lock held by swapper/0/0:
[ 21.761931] #0: ffff00008be2d8c0 (&master->lock){-...}-{2:2}, at: ipmb_slave_cb+0x70/0x208 [ipmb_host]
[ 21.771320]
               stack backtrace:
[ 21.775664] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.8.12+ #1
[ 21.781656] Hardware name: https://www.mellanox.com BlueField-3 DPU/BlueField-3 DPU, BIOS 4.13.0.13780 Sep 30 2025
[ 21.791986] Call trace:
[ 21.794419] dump_backtrace+0xa0/0x128
[ 21.798154] show_stack+0x20/0x38
[ 21.801455] dump_stack_lvl+0xec/0x150
[ 21.805192] dump_stack+0x18/0x28
[ 21.808494] print_usage_bug.part.0+0x2a4/0x3c0
[ 21.813012] mark_lock+0x4d4/0x710
[ 21.816401] __lock_acquire+0x938/0x1ae8
[ 21.820311] lock_acquire+0x118/0x300
[ 21.823961] fs_reclaim_acquire+0xd8/0xf8
[ 21.827957] kmalloc_trace+0x60/0x2f0
[ 21.831607] ipmb_slave_cb+0x140/0x208 [ipmb_host]
[ 21.836384] i2c_slave_event+0x34/0x160
[ 21.840207] mlxbf_i2c_irq_recv.isra.0+0x258/0x2b0 [i2c_mlxbf]
[ 21.846028] mlxbf_i2c_irq+0x12c/0x1f0 [i2c_mlxbf]
[ 21.850804] __handle_irq_event_percpu+0xb0/0x328
[ 21.855495] handle_irq_event+0x54/0xe0

[Fix]
The lockdep warning shows an inconsistent lock state problem
with the following critical issues:
1) Memory allocation in IRQ context: The ipmb_slave_cb() function
   (called from IRQ handler mlxbf_i2c_irq) is calling kmalloc() with
   GFP_KERNEL flag, which can trigger memory reclaim and sleep.
   This is not allowed in interrupt context.
2) Incorrect spinlock usage: The ipmb_slave_cb() function uses
   spin_lock() instead of spin_lock_irqsave(). Since this function is
   called from interrupt context, it needs to use the IRQ-safe version.

[Test Case]
Build a custom kernel with the following two settings:
  CONFIG_PROVE_LOCKING=y
  CONFIG_LOCK_STAT=y
Boot this kernel on BF3
Verify that 'dmesg' output shows no lock-related warnings

[Regression Potential]
Low

David Thompson (1):
  UBUNTU: SAUCE: ipmb_host: resolve lockdep warnings

 drivers/char/ipmi/ipmb_host.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

-- 
2.43.2