sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 101 insertions, 0 deletions

diff --git a/drivers/video/fbdev/sa1100fb.h b/drivers/video/fbdev/sa1100fb.h
new file mode 100644
index 000000000..b4363444f
--- /dev/null
+++ b/drivers/video/fbdev/sa1100fb.h
@@ -0,0 +1,101 @@
+/*
+ * linux/drivers/video/sa1100fb.h
+ *    -- StrongARM 1100 LCD Controller Frame Buffer Device
+ *
+ *  Copyright (C) 1999 Eric A. Thomas
+ *   Based on acornfb.c Copyright (C) Russell King.
+ *  
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+struct gpio_desc;
+
+#define LCCR0           0x0000          /* LCD Control Reg. 0 */
+#define LCSR            0x0004          /* LCD Status Reg. */
+#define DBAR1           0x0010          /* LCD DMA Base Address Reg. channel 1 */
+#define DCAR1           0x0014          /* LCD DMA Current Address Reg. channel 1 */
+#define DBAR2           0x0018          /* LCD DMA Base Address Reg.  channel 2 */
+#define DCAR2           0x001C          /* LCD DMA Current Address Reg. channel 2 */
+#define LCCR1           0x0020          /* LCD Control Reg. 1 */
+#define LCCR2           0x0024          /* LCD Control Reg. 2 */
+#define LCCR3           0x0028          /* LCD Control Reg. 3 */
+
+/* Shadows for LCD controller registers */
+struct sa1100fb_lcd_reg {
+	unsigned long lccr0;
+	unsigned long lccr1;
+	unsigned long lccr2;
+	unsigned long lccr3;
+};
+
+struct sa1100fb_info {
+	struct fb_info		fb;
+	struct device		*dev;
+	const struct sa1100fb_rgb *rgb[NR_RGB];
+	void __iomem		*base;
+	struct gpio_desc	*shannon_lcden;
+
+	/*
+	 * These are the addresses we mapped
+	 * the framebuffer memory region to.
+	 */
+	dma_addr_t		map_dma;
+	u_char *		map_cpu;
+	u_int			map_size;
+
+	u_char *		screen_cpu;
+	dma_addr_t		screen_dma;
+	u16 *			palette_cpu;
+	dma_addr_t		palette_dma;
+	u_int			palette_size;
+
+	dma_addr_t		dbar1;
+	dma_addr_t		dbar2;
+
+	u_int			reg_lccr0;
+	u_int			reg_lccr1;
+	u_int			reg_lccr2;
+	u_int			reg_lccr3;
+
+	volatile u_char		state;
+	volatile u_char		task_state;
+	struct mutex		ctrlr_lock;
+	wait_queue_head_t	ctrlr_wait;
+	struct work_struct	task;
+
+#ifdef CONFIG_CPU_FREQ
+	struct notifier_block	freq_transition;
+#endif
+
+	const struct sa1100fb_mach_info *inf;
+	struct clk *clk;
+
+	u32 pseudo_palette[16];
+};
+
+#define TO_INF(ptr,member)	container_of(ptr,struct sa1100fb_info,member)
+
+#define SA1100_PALETTE_MODE_VAL(bpp)    (((bpp) & 0x018) << 9)
+
+/*
+ * These are the actions for set_ctrlr_state
+ */
+#define C_DISABLE		(0)
+#define C_ENABLE		(1)
+#define C_DISABLE_CLKCHANGE	(2)
+#define C_ENABLE_CLKCHANGE	(3)
+#define C_REENABLE		(4)
+#define C_DISABLE_PM		(5)
+#define C_ENABLE_PM		(6)
+#define C_STARTUP		(7)
+
+#define SA1100_NAME	"SA1100"
+
+/*
+ * Minimum X and Y resolutions
+ */
+#define MIN_XRES	64
+#define MIN_YRES	64
+