Claude review: drm/i915/gt: Use IS_ERR() check for kernel_context() in selftests

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Correctness of the core fix: Good.** The commit message accurately describes the problem: `kernel_context()` returns an error pointer on failure, so `!ctx` checks are dead code that won't catch allocation failures. The fix is the right pattern.

**Four call sites fixed correctly:**

1. **`live_preempt()`** (line 1744): `ctx_hi` — straightforward early return, correct.
2. **`live_preempt()`** (line 1749): `ctx_lo` — correctly captures `PTR_ERR(ctx_lo)` into `err` before `goto err_ctx_hi`, since the previous code was relying on the `err = -ENOMEM` initializer which would have been wrong for a different error code.
3. **`live_late_preempt()`** (lines 1838, 1842): Same pattern, correct.
4. **`preempt_client_init()`** (line 1940): Direct return of `PTR_ERR`, correct.
5. **`live_preempt_timeout()`** (lines 3390, 3395): Same pattern as `live_preempt`, correct.

**Issue: Missed call site in the same file.**

At `selftest_execlists.c:3685`:
```c
smoke.contexts[n] = kernel_context(smoke.gt->i915, NULL);
if (!smoke.contexts[n])
    goto err_ctx;
```
This has the identical bug but was not fixed. The `err_ctx` cleanup path iterates `smoke.contexts[]` and calls `kernel_context_close()` on each, so storing an `ERR_PTR` there would also cause a crash during cleanup. The fix here requires both converting the check to `IS_ERR()` and clearing the pointer (or otherwise guarding the cleanup loop). Since the commit message claims to fix this pattern in the file, this omission should be addressed.

**Minor style note:** The added braces around single-statement `goto` blocks (e.g., `if (IS_ERR(ctx_lo)) { err = PTR_ERR(ctx_lo); goto err_ctx_hi; }`) are correct since these are now multi-statement blocks (assignment + goto).

**Recommendation:** Request a v2 that also fixes the `live_preempt_smoke()` site at line 3685, and ideally audits other selftest files for the same pattern.

---
Generated by Claude Code Patch Reviewer