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| author | Hui Su <sh_def@163.com> | 2026-08-07 23:09:55 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-09-01 12:14:29 +0200 |
| commit | f576944a59f31bcffff121117ebf452c5dd162b7 (patch) | |
| tree | 0e84f0903bd1ad82a60821b8d1087e7ecc9225c2 | |
| parent | cee9395acd8043be0644b25c34bfa86623f2b935 (diff) | |
| download | linux-f576944a59f31bcffff121117ebf452c5dd162b7.tar.gz linux-f576944a59f31bcffff121117ebf452c5dd162b7.zip | |
staging: fbtft: make dirty_lock IRQ-safe
fbtft_mkdirty() can be reached from the fbcon rendering path while
processing printk() in hardirq context. Meanwhile, dirty_lock is also
taken by fbtft_deferred_io() in workqueue context with local interrupts
enabled.
Lockdep reports a possible IRQ lock inversion involving dirty_lock and
console_owner. A hardirq can interrupt a CPU holding dirty_lock and
enter the console rendering path, which can attempt to acquire
dirty_lock again.
The following lockdep report was observed on an RK3566 system with
CONFIG_PROVE_LOCKING enabled:
WARNING: possible irq lock inversion dependency detected
swapper/2/0 just changed the state of lock:
(console_owner){-...}-{0:0}
but this lock took another, HARDIRQ-unsafe lock in the past:
(&par->dirty_lock){+.+.}-{2:2}
CPU0 CPU1
---- ----
lock(&par->dirty_lock);
local_irq_disable();
lock(console_owner);
lock(&par->dirty_lock);
<Interrupt>
lock(console_owner);
*** DEADLOCK ***
Use spin_lock_irqsave() for fbtft_mkdirty() and spin_lock_irq() for
fbtft_deferred_io(). They only access the dirty line range, so the
IRQ-off regions remain short.
Fixes: c296d5f9957c ("staging: fbtft: core support")
Signed-off-by: Hui Su <sh_def@163.com>
Link: https://lore.kernel.org/lkml/20260804173712.176017-1-sh_def@163.com/
Reviewed-by: Nam Cao <namcao@linutronix.de>
Link: https://patch.msgid.link/20260807150953.2811933-3-sh_def@163.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/staging/fbtft/fbtft-core.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c index ca0c38221c16..7925d974de80 100644 --- a/drivers/staging/fbtft/fbtft-core.c +++ b/drivers/staging/fbtft/fbtft-core.c @@ -298,14 +298,15 @@ 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); + 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); @@ -318,13 +319,13 @@ static void fbtft_deferred_io(struct fb_info *info, struct list_head *pagereflis struct fb_deferred_io_pageref *pageref; unsigned int y_low = 0, y_high = 0; - spin_lock(&par->dirty_lock); + spin_lock_irq(&par->dirty_lock); 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_irq(&par->dirty_lock); /* Mark display lines as dirty */ list_for_each_entry(pageref, pagereflist, list) { |