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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-19 10:09:22 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-19 10:09:22 -0700 |
| commit | f4cdf7ca9a1fdcca413157df19753f388a5a224e (patch) | |
| tree | 60a31895b2446cd7fa27514e8c2843534a0de0da /lib/dynamic_queue_limits.c | |
| download | linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.tar.gz linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.zip | |
Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-mediagrafted
Pull media updates from Mauro Carvalho Chehab:
- v4l2-core: added ISP statistics support and per-block validation
- v4l2-core: Allow unknown HDR10 white point and luminance
- New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor
- New codec: Milos: VPU v2.0 codec support
- isp driver: gained support for Dreamchip RPPX1 ISP framework
- vsp1 driver: gained support for RZ/T2H and RZ/N2H
- Novalake driver: gained CVS support for new NVL hardware
- dvb-core: fix feed leak on failed DMX_ADD_PID
- several driver fixes, cleanups and minor improvements
* tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits)
media: ipu-bridge: check all DMI entries when overriding sensor rotation
media: v4l2-async: avoid deleting unlinked ASC entry on link error
media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement
media: intel/ipu6: fix async notifier cleanup leak on parse error
media: staging/ipu7: fix async notifier UAF on probe error path
media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path
media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem()
media: rcar-isp: Fix VSPX reference leaks
media: rcar-isp: Release ISPCORE resources
media: i2c: imx415: Release runtime PM reference on VBLANK error
media: i2c: imx415: Return test pattern write errors
media: renesas: vsp1: Declare index variables in for loop statement
media: renesas: vsp1: Make reset control optional to support platforms without a reset line
media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs
media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs
media: nxp: imx8-isi: Add additional 32-bit RGB format support
media: nxp: imx8-isi: Add 16-bit raw Bayer format support
media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams
media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks
media: nxp: imx8-isi: Correct color map between V4L2 and ISI
...
Diffstat (limited to 'lib/dynamic_queue_limits.c')
| -rw-r--r-- | lib/dynamic_queue_limits.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c new file mode 100644 index 000000000..f97a752e9 --- /dev/null +++ b/lib/dynamic_queue_limits.c @@ -0,0 +1,217 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Dynamic byte queue limits. See include/linux/dynamic_queue_limits.h + * + * Copyright (c) 2011, Tom Herbert <therbert@google.com> + */ +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/jiffies.h> +#include <linux/dynamic_queue_limits.h> +#include <linux/compiler.h> +#include <linux/export.h> +#include <trace/events/napi.h> + +#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0) +#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0) + +static void dql_check_stall(struct dql *dql, unsigned short stall_thrs) +{ + unsigned long now; + + if (!stall_thrs) + return; + + now = jiffies; + /* Check for a potential stall */ + if (time_after_eq(now, dql->last_reap + stall_thrs)) { + unsigned long hist_head, t, start, end; + + /* We are trying to detect a period of at least @stall_thrs + * jiffies without any Tx completions, but during first half + * of which some Tx was posted. + */ +dqs_again: + hist_head = READ_ONCE(dql->history_head); + /* pairs with smp_wmb() in dql_queued() */ + smp_rmb(); + + /* Get the previous entry in the ring buffer, which is the + * oldest sample. + */ + start = (hist_head - DQL_HIST_LEN + 1) * BITS_PER_LONG; + + /* Advance start to continue from the last reap time */ + if (time_before(start, dql->last_reap + 1)) + start = dql->last_reap + 1; + + /* Newest sample we should have already seen a completion for */ + end = hist_head * BITS_PER_LONG + (BITS_PER_LONG - 1); + + /* Shrink the search space to [start, (now - start_thrs/2)] if + * `end` is beyond the stall zone + */ + if (time_before(now, end + stall_thrs / 2)) + end = now - stall_thrs / 2; + + /* Search for the queued time in [t, end] */ + for (t = start; time_before_eq(t, end); t++) + if (test_bit(t % (DQL_HIST_LEN * BITS_PER_LONG), + dql->history)) + break; + + /* Variable t contains the time of the queue */ + if (!time_before_eq(t, end)) + goto no_stall; + + /* The ring buffer was modified in the meantime, retry */ + if (hist_head != READ_ONCE(dql->history_head)) + goto dqs_again; + + dql->stall_cnt++; + dql->stall_max = max_t(unsigned short, dql->stall_max, now - t); + + trace_dql_stall_detected(dql->stall_thrs, now - t, + dql->last_reap, dql->history_head, + now, dql->history); + } +no_stall: + dql->last_reap = now; +} + +/* Records completed count and recalculates the queue limit */ +void dql_completed(struct dql *dql, unsigned int count) +{ + unsigned int inprogress, prev_inprogress, limit; + unsigned int ovlimit, completed, num_queued; + unsigned short stall_thrs; + bool all_prev_completed; + + num_queued = READ_ONCE(dql->num_queued); + /* Read stall_thrs in advance since it belongs to the same (first) + * cache line as ->num_queued. This way, dql_check_stall() does not + * need to touch the first cache line again later, reducing the window + * of possible false sharing. + */ + stall_thrs = READ_ONCE(dql->stall_thrs); + + /* Can't complete more than what's in queue */ + BUG_ON(count > num_queued - dql->num_completed); + + completed = dql->num_completed + count; + limit = dql->limit; + ovlimit = POSDIFF(num_queued - dql->num_completed, limit); + inprogress = num_queued - completed; + prev_inprogress = dql->prev_num_queued - dql->num_completed; + all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued); + + if ((ovlimit && !inprogress) || + (dql->prev_ovlimit && all_prev_completed)) { + /* + * Queue considered starved if: + * - The queue was over-limit in the last interval, + * and there is no more data in the queue. + * OR + * - The queue was over-limit in the previous interval and + * when enqueuing it was possible that all queued data + * had been consumed. This covers the case when queue + * may have becomes starved between completion processing + * running and next time enqueue was scheduled. + * + * When queue is starved increase the limit by the amount + * of bytes both sent and completed in the last interval, + * plus any previous over-limit. + */ + limit += POSDIFF(completed, dql->prev_num_queued) + + dql->prev_ovlimit; + dql->slack_start_time = jiffies; + dql->lowest_slack = UINT_MAX; + } else if (inprogress && prev_inprogress && !all_prev_completed) { + /* + * Queue was not starved, check if the limit can be decreased. + * A decrease is only considered if the queue has been busy in + * the whole interval (the check above). + * + * If there is slack, the amount of excess data queued above + * the amount needed to prevent starvation, the queue limit + * can be decreased. To avoid hysteresis we consider the + * minimum amount of slack found over several iterations of the + * completion routine. + */ + unsigned int slack, slack_last_objs; + + /* + * Slack is the maximum of + * - The queue limit plus previous over-limit minus twice + * the number of objects completed. Note that two times + * number of completed bytes is a basis for an upper bound + * of the limit. + * - Portion of objects in the last queuing operation that + * was not part of non-zero previous over-limit. That is + * "round down" by non-overlimit portion of the last + * queueing operation. + */ + slack = POSDIFF(limit + dql->prev_ovlimit, + 2 * (completed - dql->num_completed)); + slack_last_objs = dql->prev_ovlimit ? + POSDIFF(dql->prev_last_obj_cnt, dql->prev_ovlimit) : 0; + + slack = max(slack, slack_last_objs); + + if (slack < dql->lowest_slack) + dql->lowest_slack = slack; + + if (time_after(jiffies, + dql->slack_start_time + dql->slack_hold_time)) { + limit = POSDIFF(limit, dql->lowest_slack); + dql->slack_start_time = jiffies; + dql->lowest_slack = UINT_MAX; + } + } + + /* Enforce bounds on limit */ + limit = clamp(limit, dql->min_limit, dql->max_limit); + + if (limit != dql->limit) { + dql->limit = limit; + ovlimit = 0; + } + + dql->adj_limit = limit + completed; + dql->prev_ovlimit = ovlimit; + dql->prev_last_obj_cnt = READ_ONCE(dql->last_obj_cnt); + dql->num_completed = completed; + dql->prev_num_queued = num_queued; + + dql_check_stall(dql, stall_thrs); +} +EXPORT_SYMBOL(dql_completed); + +void dql_reset(struct dql *dql) +{ + /* Reset all dynamic values */ + dql->limit = dql->min_limit; + dql->num_queued = 0; + dql->num_completed = 0; + dql->last_obj_cnt = 0; + dql->prev_num_queued = 0; + dql->prev_last_obj_cnt = 0; + dql->prev_ovlimit = 0; + dql->lowest_slack = UINT_MAX; + dql->slack_start_time = jiffies; + + dql->last_reap = jiffies; + dql->history_head = jiffies / BITS_PER_LONG; + memset(dql->history, 0, sizeof(dql->history)); +} +EXPORT_SYMBOL(dql_reset); + +void dql_init(struct dql *dql, unsigned int hold_time) +{ + dql->max_limit = DQL_MAX_LIMIT; + dql->min_limit = 0; + dql->slack_hold_time = hold_time; + dql->stall_thrs = 0; + dql_reset(dql); +} +EXPORT_SYMBOL(dql_init); |
