Re: [PATCH] staging: fbtft: make dirty_lock IRQ-safe
From: Nam Cao <hidden>
Date: 2026-08-07 12:53:37
Also in:
dri-devel, linux-staging, lkml
sh_def@163.com writes:
quoted hunk ↗ jump to hunk
diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c index ca0c38221c16..193643d0329d 100644 --- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c@@ -298,14 +298,20 @@ static void fbtft_mkdirty(struct fb_info *info, int y, int height) { struct fbtft_par *par = info->par; struct fb_deferred_io *fbdefio = info->fbdefio; + unsigned long flags; /* Mark display lines/area as dirty */ - spin_lock(&par->dirty_lock); + /* + * fbcon takes dirty_lock while holding console_owner. Disable local + * interrupts here so a printk hardirq cannot acquire console_owner + * while dirty_lock is held and create the inverse lock ordering. + */
Beside that reason, we also need spin_lock_irqsave() because fbtft_mkdirty() can be called in both task context and hardirq context. And this reason alone suffices and usually is why spin_lock_irqsave() is used, so I think a comment is not necessary. But I am fine with it either way.
quoted hunk ↗ jump to hunk
+ spin_lock_irqsave(&par->dirty_lock, flags); if (y < par->dirty_lines_start) par->dirty_lines_start = y; if (y + height - 1 > par->dirty_lines_end) par->dirty_lines_end = y + height - 1; - spin_unlock(&par->dirty_lock); + spin_unlock_irqrestore(&par->dirty_lock, flags); /* Schedule deferred_io to update display (no-op if already on queue)*/ schedule_delayed_work(&info->deferred_work, fbdefio->delay);@@ -317,14 +323,15 @@ static void fbtft_deferred_io(struct fb_info *info, struct list_head *pagereflis unsigned int dirty_lines_start, dirty_lines_end; struct fb_deferred_io_pageref *pageref; unsigned int y_low = 0, y_high = 0; + unsigned long flags; - spin_lock(&par->dirty_lock); + spin_lock_irqsave(&par->dirty_lock, flags); dirty_lines_start = par->dirty_lines_start; dirty_lines_end = par->dirty_lines_end; /* set display line markers as clean */ par->dirty_lines_start = par->info->var.yres - 1; par->dirty_lines_end = 0; - spin_unlock(&par->dirty_lock); + spin_unlock_irqrestore(&par->dirty_lock, flags);
fbtft_deferred_io() is executed in workqueue with interrupt enabled. So it can use spin_lock_irq() instead of spin_lock_irqsave(), right? Nam