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…render thread competing with BWM
Three categories of fixes for ARM64 interactive mode lockups:
1. **Null-terminated paths for kernel syscalls** (libs/libbreenix/src/fs.rs)
Add CPath struct that ensures all path strings passed to kernel syscalls
are properly null-terminated with write_volatile. Rust &str is NOT null-
terminated, and the compiler can optimize away zero bytes after the string
data. Applied to all 11 path-taking functions: open, open_with_mode,
access, unlink, mkdir, rmdir, rename, link, symlink, readlink, mkfifo.
2. **Drop PROCESS_MANAGER before I/O in sys_poll and sys_select**
(kernel/src/syscall/handlers.rs)
On ARM64, process::manager() disables ALL interrupts (DAIF mask 0xF).
Previously sys_poll/sys_select held PM across the entire poll loop
including PTY buffer locks, TCP connection locks, etc. Now they snapshot
fd entries under PM (cheap Arc::clone), drop PM, then iterate. This
follows the same extract-then-drop pattern used by sys_read/sys_write.
3. **Render thread stops competing with BWM for GPU** (render_task.rs,
graphics.rs, handlers.rs)
- Add DISPLAY_TAKEN flag set by sys_take_over_display(). Render thread
skips framebuffer flush and cursor updates when BWM owns the display
(standard pattern — same as Linux fbcon KD_GRAPHICS mode).
- Move PROCESS_MANAGER acquisition in sys_fbdraw BEFORE the
SHELL_FRAMEBUFFER lock. Previously PM (interrupts disabled) was
acquired nested inside the framebuffer lock during GPU busy-waits.
- Remove all diagnostic serial_println/print! from previous debugging.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
write_volatileto ensure null-terminated paths. Rust&stris NOT null-terminated and the compiler can optimize away trailing zeroes, causing the kernel'scopy_cstr_from_user()to read garbage.DISPLAY_TAKENflag (standard fbcon/KD_GRAPHICS pattern) so the render thread stops competing with BWM forSHELL_FRAMEBUFFERduring GPU busy-waits. Also move PM acquisition before FB lock insys_fbdrawto prevent nested interrupt-masking inside long-held spinlocks.serial_println!/print!from previous debugging sessions.Test plan
run-aarch64-boot-test-native.sh)run-boot-parallel.sh 1)🤖 Generated with Claude Code