Re: [PATCH v6 8/8] drm/xe: Avoid toggling schedule state to check LRC timestamp in TDR

[Dan Carpenter <dan.carpenter@linaro.org>]

Hi Matthew,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Matthew-Brost/drm-sched-Add-several-job-helpers-to-avoid-drivers-touching-scheduler-state/20251127-054955
base:   https://gitlab.freedesktop.org/drm/xe/kernel.git drm-xe-next
patch link:    https://lore.kernel.org/r/20251126214748.650107-9-matthew.brost%40intel.com
patch subject: [PATCH v6 8/8] drm/xe: Avoid toggling schedule state to check LRC timestamp in TDR
config: x86_64-randconfig-161-20251128 (https://download.01.org/0day-ci/archive/20251129/202511291102.jnnKP6IB-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202511291102.jnnKP6IB-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/xe/xe_lrc.c:2392 xe_lrc_timestamp() error: uninitialized symbol 'new_ts'.

vim +/new_ts +2392 drivers/gpu/drm/xe/xe_lrc.c

94c0c481e1bd20 Matthew Brost         2025-11-26  2363  u64 xe_lrc_timestamp(struct xe_lrc *lrc)
9b090d57746d96 Umesh Nerlige Ramappa 2024-05-17  2364  {
94c0c481e1bd20 Matthew Brost         2025-11-26  2365  	u64 lrc_ts, reg_ts, new_ts;
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2366  	u32 engine_id;
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2367  
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2368  	lrc_ts = xe_lrc_ctx_timestamp(lrc);
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2369  	/* CTX_TIMESTAMP mmio read is invalid on VF, so return the LRC value */
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2370  	if (IS_SRIOV_VF(lrc_to_xe(lrc))) {
94c0c481e1bd20 Matthew Brost         2025-11-26  2371  		new_ts = lrc_ts;
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2372  		goto done;
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2373  	}
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2374  
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2375  	if (lrc_ts == CONTEXT_ACTIVE) {
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2376  		engine_id = xe_lrc_engine_id(lrc);
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2377  		if (!get_ctx_timestamp(lrc, engine_id, &reg_ts))
94c0c481e1bd20 Matthew Brost         2025-11-26  2378  			new_ts = reg_ts;

uninitialized on else path.

82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2379  
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2380  		/* read lrc again to ensure context is still active */
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2381  		lrc_ts = xe_lrc_ctx_timestamp(lrc);

lrc_ts is re-assigned here.

82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2382  	}
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2383  
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2384  	/*
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2385  	 * If context switched out, just use the lrc_ts. Note that this needs to
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2386  	 * be a separate if condition.
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2387  	 */
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2388  	if (lrc_ts != CONTEXT_ACTIVE)
94c0c481e1bd20 Matthew Brost         2025-11-26  2389  		new_ts = lrc_ts;

uninitialized on else path.

9b090d57746d96 Umesh Nerlige Ramappa 2024-05-17  2390  
82b98cadb01f63 Umesh Nerlige Ramappa 2025-05-09  2391  done:
94c0c481e1bd20 Matthew Brost         2025-11-26 @2392  	return new_ts;
94c0c481e1bd20 Matthew Brost         2025-11-26  2393  }

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