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[PATCH 1/2] writeback: fix 100% CPU usage when dirtytime_expire_interval is 0

by Laveesh Bansal

When vm.dirtytime_expire_seconds is set to 0, wakeup_dirtytime_writeback() schedules delayed work with a delay of 0, causing immediate execution. The function then reschedules itself with 0 delay again, creating an infinite busy loop that causes 100% kworker CPU usage. Fix by: - Only scheduling delayed work in wakeup_dirtytime_writeback() when dirtytime_expire_interval is non-zero - Cancelling the delayed work in dirtytime_interval_handler() when the interval is set to 0 - Adding a guard in start_dirtytime_writeback() for defensive coding Tested by booting kernel in QEMU with virtme-ng: - Before fix: kworker CPU spikes to ~73% - After fix: CPU remains at normal levels - Setting interval back to non-zero correctly resumes writeback Fixes: a2f4870697a5 ("fs: make sure the timestamps for lazytime inodes eventually get written") Cc: stable(a)vger.kernel.org Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220227 Signed-off-by: Laveesh Bansal <laveeshb(a)laveeshbansal.com> --- fs/fs-writeback.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 6800886c4d10..cd21c74cd0e5 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -2492,7 +2492,8 @@ static void wakeup_dirtytime_writeback(struct work_struct *w) wb_wakeup(wb); } rcu_read_unlock(); - schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); + if (dirtytime_expire_interval) + schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); } static int dirtytime_interval_handler(const struct ctl_table *table, int write, @@ -2501,8 +2502,12 @@ static int dirtytime_interval_handler(const struct ctl_table *table, int write, int ret; ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); - if (ret == 0 && write) - mod_delayed_work(system_percpu_wq, &dirtytime_work, 0); + if (ret == 0 && write) { + if (dirtytime_expire_interval) + mod_delayed_work(system_percpu_wq, &dirtytime_work, 0); + else + cancel_delayed_work_sync(&dirtytime_work); + } return ret; } @@ -2519,7 +2524,8 @@ static const struct ctl_table vm_fs_writeback_table[] = { static int __init start_dirtytime_writeback(void) { - schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); + if (dirtytime_expire_interval) + schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); register_sysctl_init("vm", vm_fs_writeback_table); return 0; } -- 2.43.0

1 week, 4 days

[PATCH 1/2] writeback: fix 100% CPU usage when dirtytime_expire_interval is 0

by Laveesh Bansal

From: Laveesh Bansal <laveeshbansal(a)gmail.com> When vm.dirtytime_expire_seconds is set to 0, wakeup_dirtytime_writeback() schedules delayed work with a delay of 0, causing immediate execution. The function then reschedules itself with 0 delay again, creating an infinite busy loop that causes 100% kworker CPU usage. Fix by: - Only scheduling delayed work in wakeup_dirtytime_writeback() when dirtytime_expire_interval is non-zero - Cancelling the delayed work in dirtytime_interval_handler() when the interval is set to 0 - Adding a guard in start_dirtytime_writeback() for defensive coding Tested by booting kernel in QEMU with virtme-ng: - Before fix: kworker CPU spikes to ~73% - After fix: CPU remains at normal levels - Setting interval back to non-zero correctly resumes writeback Fixes: a2f4870697a5 ("fs: make sure the timestamps for lazytime inodes eventually get written") Cc: stable(a)vger.kernel.org Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220227 Signed-off-by: Laveesh Bansal <laveeshbansal(a)gmail.com> --- fs/fs-writeback.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 6800886c4d10..cd21c74cd0e5 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -2492,7 +2492,8 @@ static void wakeup_dirtytime_writeback(struct work_struct *w) wb_wakeup(wb); } rcu_read_unlock(); - schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); + if (dirtytime_expire_interval) + schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); } static int dirtytime_interval_handler(const struct ctl_table *table, int write, @@ -2501,8 +2502,12 @@ static int dirtytime_interval_handler(const struct ctl_table *table, int write, int ret; ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); - if (ret == 0 && write) - mod_delayed_work(system_percpu_wq, &dirtytime_work, 0); + if (ret == 0 && write) { + if (dirtytime_expire_interval) + mod_delayed_work(system_percpu_wq, &dirtytime_work, 0); + else + cancel_delayed_work_sync(&dirtytime_work); + } return ret; } @@ -2519,7 +2524,8 @@ static const struct ctl_table vm_fs_writeback_table[] = { static int __init start_dirtytime_writeback(void) { - schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); + if (dirtytime_expire_interval) + schedule_delayed_work(&dirtytime_work, dirtytime_expire_interval * HZ); register_sysctl_init("vm", vm_fs_writeback_table); return 0; } -- 2.43.0

1 week, 4 days

Re: NRF 2026 Retail's Big Show more information

by Amy Giles

Hi, I wanted to see if you had time to review the email I sent earlier. Should you need any other details, don't hesitate to reach out. Best Amy Giles Please reply with REMOVE if you don't wish to receive further emails -----Original Message----- Hi, Hope you're having a great day! Are you looking for leads from NRF 2026 Retail's Big Show? Attendees count: 30,000 Leads Data Fields: Company Name, Web URL, Contact Name, Title, Direct Email, Phone Number, Mailing Address, Industry, Employee Size, Annual Sales. If you're interested in these leads, I'd be glad to share the pricing. Let me know! Thanks for the quick reply. I'm excited to get your thoughts. Best Amy Giles Demand Generation Manager Zoom Connect, Inc Please reply with REMOVE if you don't wish to receive further emails

1 week, 4 days

RE: CES 2026: Audience Breakdown & Leads

by Jessica Garcia

Hi , Just touching base to see if you're available to discuss this further. If you have any uncertainties, I'm happy to help. Regards Jessica Marketing Manager Campaign Data Leads., Please reply with REMOVE if you don't wish to receive further emails -----Original Message----- From: Jessica Garcia Subject: CES 2026: Audience Breakdown & Leads Hi , Trust you're in good spirits. Is the idea of buying the CES 2026 attendees' details for your marketing efforts something you'd like to explore? Expo Name: Consumer Electronics Show 2026 Total Number of records: 40,000 records List includes: Company Name, Contact Name, Job Title, Mailing Address, Phone, Emails, etc. Best chance to connect with participants Feel free to contact me if you are interested in acquiring this list so that I can share pricing information with you Hoping for your prompt feedback. Regards Jessica Marketing Manager Campaign Data Leads., Please reply with REMOVE if you don't wish to receive further emails

1 week, 4 days

[PATCH 2/5] ARM: dts: microchip: sama7d65: fix size-cells property for i2c3

by nicolas.ferre＠microchip.com

From: Nicolas Ferre <nicolas.ferre(a)microchip.com> Fix the #size-cells property for i2c3 node and remove the dtbs_check error telling that "#size-cells: 0 was expected" from schema atmel,at91sam-i2c.yaml and i2c-controller.yaml. Fixes: b51e4aea3ecf ("ARM: dts: microchip: sama7d65: Add FLEXCOMs to sama7d65 SoC") Cc: <stable(a)vger.kernel.org> # 6.16+ Signed-off-by: Nicolas Ferre <nicolas.ferre(a)microchip.com> --- arch/arm/boot/dts/microchip/sama7d65.dtsi | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/boot/dts/microchip/sama7d65.dtsi b/arch/arm/boot/dts/microchip/sama7d65.dtsi index 5f3a7b178aa7..868045c650a7 100644 --- a/arch/arm/boot/dts/microchip/sama7d65.dtsi +++ b/arch/arm/boot/dts/microchip/sama7d65.dtsi @@ -527,7 +527,7 @@ i2c3: i2c@600 { interrupts = <GIC_SPI 37 IRQ_TYPE_LEVEL_HIGH>; clocks = <&pmc PMC_TYPE_PERIPHERAL 37>; #address-cells = <1>; - #size-cells = <1>; + #size-cells = <0>; dmas = <&dma0 AT91_XDMAC_DT_PERID(12)>, <&dma0 AT91_XDMAC_DT_PERID(11)>; dma-names = "tx", "rx"; -- 2.43.0

1 week, 4 days

[PATCH 1/5] ARM: dts: microchip: sama7d65: fix the ranges property for flx9

by nicolas.ferre＠microchip.com

From: Hari Prasath Gujulan Elango <hari.prasathge(a)microchip.com> Update the ranges property for the flexcom9 as per the datasheet and align with the reg property. Fixes: b51e4aea3ecf ("ARM: dts: microchip: sama7d65: Add FLEXCOMs to sama7d65 SoC") Cc: <stable(a)vger.kernel.org> # 6.16+ Signed-off-by: Hari Prasath Gujulan Elango <hari.prasathge(a)microchip.com> Signed-off-by: Nicolas Ferre <nicolas.ferre(a)microchip.com> --- Note: Hari's email address will bounce. Change to whichever suits you. arch/arm/boot/dts/microchip/sama7d65.dtsi | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/boot/dts/microchip/sama7d65.dtsi b/arch/arm/boot/dts/microchip/sama7d65.dtsi index cd2cf9a6f40b..5f3a7b178aa7 100644 --- a/arch/arm/boot/dts/microchip/sama7d65.dtsi +++ b/arch/arm/boot/dts/microchip/sama7d65.dtsi @@ -676,7 +676,7 @@ i2c8: i2c@600 { flx9: flexcom@e2820000 { compatible = "microchip,sama7d65-flexcom", "atmel,sama5d2-flexcom"; reg = <0xe2820000 0x200>; - ranges = <0x0 0xe281c000 0x800>; + ranges = <0x0 0xe2820000 0x800>; clocks = <&pmc PMC_TYPE_PERIPHERAL 43>; #address-cells = <1>; #size-cells = <1>; -- 2.43.0

1 week, 4 days

[PATCH v2] drm/bridge: synopsys: dw-dp: return when attach bridge fail

by Osama Abdelkader

When drm_bridge_attach() fails, the function should return an error instead of continuing execution. Fixes: 86eecc3a9c2e ("drm/bridge: synopsys: Add DW DPTX Controller support library") Cc: stable(a)vger.kernel.org Signed-off-by: Osama Abdelkader <osama.abdelkader(a)gmail.com> --- v2: use concise error message add Fixes and Cc tags --- drivers/gpu/drm/bridge/synopsys/dw-dp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/bridge/synopsys/dw-dp.c b/drivers/gpu/drm/bridge/synopsys/dw-dp.c index 82aaf74e1bc0..bc311a596dff 100644 --- a/drivers/gpu/drm/bridge/synopsys/dw-dp.c +++ b/drivers/gpu/drm/bridge/synopsys/dw-dp.c @@ -2063,7 +2063,7 @@ struct dw_dp *dw_dp_bind(struct device *dev, struct drm_encoder *encoder, ret = drm_bridge_attach(encoder, bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR); if (ret) - dev_err_probe(dev, ret, "Failed to attach bridge\n"); + return ERR_PTR(dev_err_probe(dev, ret, "Failed to attach bridge\n")); dw_dp_init_hw(dp); -- 2.43.0

1 week, 4 days

FAILED: patch "[PATCH] sched/eevdf: Fix min_vruntime vs avg_vruntime" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 79f3f9bedd149ea438aaeb0fb6a083637affe205 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025122903-sterile-from-4520@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 79f3f9bedd149ea438aaeb0fb6a083637affe205 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra <peterz(a)infradead.org> Date: Wed, 2 Apr 2025 20:07:34 +0200 Subject: [PATCH] sched/eevdf: Fix min_vruntime vs avg_vruntime Basically, from the constraint that the sum of lag is zero, you can infer that the 0-lag point is the weighted average of the individual vruntime, which is what we're trying to compute: \Sum w_i * v_i avg = -------------- \Sum w_i Now, since vruntime takes the whole u64 (worse, it wraps), this multiplication term in the numerator is not something we can compute; instead we do the min_vruntime (v0 henceforth) thing like: v_i = (v_i - v0) + v0 This does two things: - it keeps the key: (v_i - v0) 'small'; - it creates a relative 0-point in the modular space. If you do that subtitution and work it all out, you end up with: \Sum w_i * (v_i - v0) avg = --------------------- + v0 \Sum w_i Since you cannot very well track a ratio like that (and not suffer terrible numerical problems) we simpy track the numerator and denominator individually and only perform the division when strictly needed. Notably, the numerator lives in cfs_rq->avg_vruntime and the denominator lives in cfs_rq->avg_load. The one extra 'funny' is that these numbers track the entities in the tree, and current is typically outside of the tree, so avg_vruntime() adds current when needed before doing the division. (vruntime_eligible() elides the division by cross-wise multiplication) Anyway, as mentioned above, we currently use the CFS era min_vruntime for this purpose. However, this thing can only move forward, while the above avg can in fact move backward (when a non-eligible task leaves, the average becomes smaller), this can cause trouble when through happenstance (or construction) these values drift far enough apart to wreck the game. Replace cfs_rq::min_vruntime with cfs_rq::zero_vruntime which is kept near/at avg_vruntime, following its motion. The down-side is that this requires computing the avg more often. Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy") Reported-by: Zicheng Qu <quzicheng(a)huawei.com> Signed-off-by: Peter Zijlstra (Intel) <peterz(a)infradead.org> Link: https://patch.msgid.link/20251106111741.GC4068168@noisy.programming.kicks-a… Cc: stable(a)vger.kernel.org diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 02e16b70a790..41caa22e0680 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -796,7 +796,7 @@ static void print_rq(struct seq_file *m, struct rq *rq, int rq_cpu) void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) { - s64 left_vruntime = -1, min_vruntime, right_vruntime = -1, left_deadline = -1, spread; + s64 left_vruntime = -1, zero_vruntime, right_vruntime = -1, left_deadline = -1, spread; struct sched_entity *last, *first, *root; struct rq *rq = cpu_rq(cpu); unsigned long flags; @@ -819,15 +819,15 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) last = __pick_last_entity(cfs_rq); if (last) right_vruntime = last->vruntime; - min_vruntime = cfs_rq->min_vruntime; + zero_vruntime = cfs_rq->zero_vruntime; raw_spin_rq_unlock_irqrestore(rq, flags); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "left_deadline", SPLIT_NS(left_deadline)); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "left_vruntime", SPLIT_NS(left_vruntime)); - SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "min_vruntime", - SPLIT_NS(min_vruntime)); + SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "zero_vruntime", + SPLIT_NS(zero_vruntime)); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "avg_vruntime", SPLIT_NS(avg_vruntime(cfs_rq))); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "right_vruntime", diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 4a11a832d63e..8d971d48669f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -554,7 +554,7 @@ static inline bool entity_before(const struct sched_entity *a, static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se) { - return (s64)(se->vruntime - cfs_rq->min_vruntime); + return (s64)(se->vruntime - cfs_rq->zero_vruntime); } #define __node_2_se(node) \ @@ -606,13 +606,13 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se) * * Which we track using: * - * v0 := cfs_rq->min_vruntime + * v0 := cfs_rq->zero_vruntime * \Sum (v_i - v0) * w_i := cfs_rq->avg_vruntime * \Sum w_i := cfs_rq->avg_load * - * Since min_vruntime is a monotonic increasing variable that closely tracks - * the per-task service, these deltas: (v_i - v), will be in the order of the - * maximal (virtual) lag induced in the system due to quantisation. + * Since zero_vruntime closely tracks the per-task service, these + * deltas: (v_i - v), will be in the order of the maximal (virtual) lag + * induced in the system due to quantisation. * * Also, we use scale_load_down() to reduce the size. * @@ -671,7 +671,7 @@ u64 avg_vruntime(struct cfs_rq *cfs_rq) avg = div_s64(avg, load); } - return cfs_rq->min_vruntime + avg; + return cfs_rq->zero_vruntime + avg; } /* @@ -732,7 +732,7 @@ static int vruntime_eligible(struct cfs_rq *cfs_rq, u64 vruntime) load += weight; } - return avg >= (s64)(vruntime - cfs_rq->min_vruntime) * load; + return avg >= (s64)(vruntime - cfs_rq->zero_vruntime) * load; } int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se) @@ -740,42 +740,14 @@ int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se) return vruntime_eligible(cfs_rq, se->vruntime); } -static u64 __update_min_vruntime(struct cfs_rq *cfs_rq, u64 vruntime) +static void update_zero_vruntime(struct cfs_rq *cfs_rq) { - u64 min_vruntime = cfs_rq->min_vruntime; - /* - * open coded max_vruntime() to allow updating avg_vruntime - */ - s64 delta = (s64)(vruntime - min_vruntime); - if (delta > 0) { - avg_vruntime_update(cfs_rq, delta); - min_vruntime = vruntime; - } - return min_vruntime; -} + u64 vruntime = avg_vruntime(cfs_rq); + s64 delta = (s64)(vruntime - cfs_rq->zero_vruntime); -static void update_min_vruntime(struct cfs_rq *cfs_rq) -{ - struct sched_entity *se = __pick_root_entity(cfs_rq); - struct sched_entity *curr = cfs_rq->curr; - u64 vruntime = cfs_rq->min_vruntime; + avg_vruntime_update(cfs_rq, delta); - if (curr) { - if (curr->on_rq) - vruntime = curr->vruntime; - else - curr = NULL; - } - - if (se) { - if (!curr) - vruntime = se->min_vruntime; - else - vruntime = min_vruntime(vruntime, se->min_vruntime); - } - - /* ensure we never gain time by being placed backwards. */ - cfs_rq->min_vruntime = __update_min_vruntime(cfs_rq, vruntime); + cfs_rq->zero_vruntime = vruntime; } static inline u64 cfs_rq_min_slice(struct cfs_rq *cfs_rq) @@ -848,6 +820,7 @@ RB_DECLARE_CALLBACKS(static, min_vruntime_cb, struct sched_entity, static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { avg_vruntime_add(cfs_rq, se); + update_zero_vruntime(cfs_rq); se->min_vruntime = se->vruntime; se->min_slice = se->slice; rb_add_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline, @@ -859,6 +832,7 @@ static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) rb_erase_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline, &min_vruntime_cb); avg_vruntime_sub(cfs_rq, se); + update_zero_vruntime(cfs_rq); } struct sched_entity *__pick_root_entity(struct cfs_rq *cfs_rq) @@ -1226,7 +1200,6 @@ static void update_curr(struct cfs_rq *cfs_rq) curr->vruntime += calc_delta_fair(delta_exec, curr); resched = update_deadline(cfs_rq, curr); - update_min_vruntime(cfs_rq); if (entity_is_task(curr)) { /* @@ -3808,15 +3781,6 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, if (!curr) __enqueue_entity(cfs_rq, se); cfs_rq->nr_queued++; - - /* - * The entity's vruntime has been adjusted, so let's check - * whether the rq-wide min_vruntime needs updated too. Since - * the calculations above require stable min_vruntime rather - * than up-to-date one, we do the update at the end of the - * reweight process. - */ - update_min_vruntime(cfs_rq); } } @@ -5429,15 +5393,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) update_cfs_group(se); - /* - * Now advance min_vruntime if @se was the entity holding it back, - * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be - * put back on, and if we advance min_vruntime, we'll be placed back - * further than we started -- i.e. we'll be penalized. - */ - if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE) - update_min_vruntime(cfs_rq); - if (flags & DEQUEUE_DELAYED) finish_delayed_dequeue_entity(se); @@ -9015,7 +8970,6 @@ static void yield_task_fair(struct rq *rq) if (entity_eligible(cfs_rq, se)) { se->vruntime = se->deadline; se->deadline += calc_delta_fair(se->slice, se); - update_min_vruntime(cfs_rq); } } @@ -13078,23 +13032,6 @@ static inline void task_tick_core(struct rq *rq, struct task_struct *curr) * Which shows that S and s_i transform alike (which makes perfect sense * given that S is basically the (weighted) average of s_i). * - * Then: - * - * x -> s_min := min{s_i} (8) - * - * to obtain: - * - * \Sum_i w_i (s_i - s_min) - * S = s_min + ------------------------ (9) - * \Sum_i w_i - * - * Which already looks familiar, and is the basis for our current - * approximation: - * - * S ~= s_min (10) - * - * Now, obviously, (10) is absolute crap :-), but it sorta works. - * * So the thing to remember is that the above is strictly UP. It is * possible to generalize to multiple runqueues -- however it gets really * yuck when you have to add affinity support, as illustrated by our very @@ -13116,23 +13053,23 @@ static inline void task_tick_core(struct rq *rq, struct task_struct *curr) * Let, for our runqueue 'k': * * T_k = \Sum_i w_i s_i - * W_k = \Sum_i w_i ; for all i of k (11) + * W_k = \Sum_i w_i ; for all i of k (8) * * Then we can write (6) like: * * T_k - * S_k = --- (12) + * S_k = --- (9) * W_k * * From which immediately follows that: * * T_k + T_l - * S_k+l = --------- (13) + * S_k+l = --------- (10) * W_k + W_l * * On which we can define a combined lag: * - * lag_k+l(i) := S_k+l - s_i (14) + * lag_k+l(i) := S_k+l - s_i (11) * * And that gives us the tools to compare tasks across a combined runqueue. * @@ -13143,7 +13080,7 @@ static inline void task_tick_core(struct rq *rq, struct task_struct *curr) * using (7); this only requires storing single 'time'-stamps. * * b) when comparing tasks between 2 runqueues of which one is forced-idle, - * compare the combined lag, per (14). + * compare the combined lag, per (11). * * Now, of course cgroups (I so hate them) make this more interesting in * that a) seems to suggest we need to iterate all cgroup on a CPU at such @@ -13191,12 +13128,11 @@ static inline void task_tick_core(struct rq *rq, struct task_struct *curr) * every tick. This limits the observed divergence due to the work * conservancy. * - * On top of that, we can improve upon things by moving away from our - * horrible (10) hack and moving to (9) and employing (13) here. + * On top of that, we can improve upon things by employing (10) here. */ /* - * se_fi_update - Update the cfs_rq->min_vruntime_fi in a CFS hierarchy if needed. + * se_fi_update - Update the cfs_rq->zero_vruntime_fi in a CFS hierarchy if needed. */ static void se_fi_update(const struct sched_entity *se, unsigned int fi_seq, bool forceidle) @@ -13210,7 +13146,7 @@ static void se_fi_update(const struct sched_entity *se, unsigned int fi_seq, cfs_rq->forceidle_seq = fi_seq; } - cfs_rq->min_vruntime_fi = cfs_rq->min_vruntime; + cfs_rq->zero_vruntime_fi = cfs_rq->zero_vruntime; } } @@ -13263,11 +13199,11 @@ bool cfs_prio_less(const struct task_struct *a, const struct task_struct *b, /* * Find delta after normalizing se's vruntime with its cfs_rq's - * min_vruntime_fi, which would have been updated in prior calls + * zero_vruntime_fi, which would have been updated in prior calls * to se_fi_update(). */ delta = (s64)(sea->vruntime - seb->vruntime) + - (s64)(cfs_rqb->min_vruntime_fi - cfs_rqa->min_vruntime_fi); + (s64)(cfs_rqb->zero_vruntime_fi - cfs_rqa->zero_vruntime_fi); return delta > 0; } @@ -13513,7 +13449,7 @@ static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first) void init_cfs_rq(struct cfs_rq *cfs_rq) { cfs_rq->tasks_timeline = RB_ROOT_CACHED; - cfs_rq->min_vruntime = (u64)(-(1LL << 20)); + cfs_rq->zero_vruntime = (u64)(-(1LL << 20)); raw_spin_lock_init(&cfs_rq->removed.lock); } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 82e74e8ca2ea..5a3cf81c27be 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -681,10 +681,10 @@ struct cfs_rq { s64 avg_vruntime; u64 avg_load; - u64 min_vruntime; + u64 zero_vruntime; #ifdef CONFIG_SCHED_CORE unsigned int forceidle_seq; - u64 min_vruntime_fi; + u64 zero_vruntime_fi; #endif struct rb_root_cached tasks_timeline;

1 week, 4 days

[PATCH 0/3] fs: add immutable rootfs and support pivot_root() in the initramfs

by Christian Brauner

Currently pivot_root() doesnt't work on the real rootfs because it cannot be unmounted. Userspace has to do a recursive removal of the initramfs contents manually before continuing the boot. Really all we want from the real rootfs is to serve as the parent mount for anything that is actually useful such as the tmpfs or ramfs for initramfs unpacking or the rootfs itself. There's no need for the real rootfs to actually be anything meaningful or useful. Add a immutable rootfs that can be selected via the "immutable_rootfs" kernel command line option. The kernel will mount a tmpfs/ramfs on top of it, unpack the initramfs and fire up userspace which mounts the rootfs and can then just do: chdir(rootfs); pivot_root(".", "."); umount2(".", MNT_DETACH); and be done with it. (Ofc, userspace can also choose to retain the initramfs contents by using something like pivot_root(".", "/initramfs") without unmounting it.) Technically this also means that the rootfs mount in unprivileged namespaces doesn't need to become MNT_LOCKED anymore as it's guaranteed that the immutable rootfs remains permanently empty so there cannot be anything revealed by unmounting the covering mount. In the future this will also allow us to create completely empty mount namespaces without risking to leak anything. systemd already handles this all correctly as it tries to pivot_root() first and falls back to MS_MOVE only when that fails. This goes back to various discussion in previous years and a LPC 2024 presentation about this very topic. Signed-off-by: Christian Brauner <brauner(a)kernel.org> --- Christian Brauner (3): fs: ensure that internal tmpfs mount gets mount id zero fs: add init_pivot_root() fs: add immutable rootfs fs/Makefile | 2 +- fs/init.c | 17 ++++ fs/internal.h | 1 + fs/mount.h | 1 + fs/namespace.c | 181 +++++++++++++++++++++++++++++------------- fs/rootfs.c | 65 +++++++++++++++ include/linux/init_syscalls.h | 1 + include/uapi/linux/magic.h | 1 + init/do_mounts.c | 13 ++- init/do_mounts.h | 1 + 10 files changed, 223 insertions(+), 60 deletions(-) --- base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8 change-id: 20260102-work-immutable-rootfs-b5f23e0f5a27

1 week, 4 days

FAILED: patch "[PATCH] sched_ext: Factor out local_dsq_post_enq() from" failed to apply to 6.12-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 530b6637c79e728d58f1d9b66bd4acf4b735b86d # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025122922-chubby-doctrine-9c07@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 530b6637c79e728d58f1d9b66bd4acf4b735b86d Mon Sep 17 00:00:00 2001 From: Tejun Heo <tj(a)kernel.org> Date: Thu, 11 Dec 2025 15:45:03 -1000 Subject: [PATCH] sched_ext: Factor out local_dsq_post_enq() from dispatch_enqueue() Factor out local_dsq_post_enq() which performs post-enqueue handling for local DSQs - triggering resched_curr() if SCX_ENQ_PREEMPT is specified or if the current CPU is idle. No functional change. This will be used by the next patch to fix move_local_task_to_local_dsq(). Cc: stable(a)vger.kernel.org # v6.12+ Reviewed-by: Andrea Righi <arighi(a)nvidia.com> Reviewed-by: Emil Tsalapatis <emil(a)etsalapatis.com> Signed-off-by: Tejun Heo <tj(a)kernel.org> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index c4465ccefea4..c78efa99406f 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -982,6 +982,22 @@ static void refill_task_slice_dfl(struct scx_sched *sch, struct task_struct *p) __scx_add_event(sch, SCX_EV_REFILL_SLICE_DFL, 1); } +static void local_dsq_post_enq(struct scx_dispatch_q *dsq, struct task_struct *p, + u64 enq_flags) +{ + struct rq *rq = container_of(dsq, struct rq, scx.local_dsq); + bool preempt = false; + + if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr && + rq->curr->sched_class == &ext_sched_class) { + rq->curr->scx.slice = 0; + preempt = true; + } + + if (preempt || sched_class_above(&ext_sched_class, rq->curr->sched_class)) + resched_curr(rq); +} + static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq, struct task_struct *p, u64 enq_flags) { @@ -1093,22 +1109,10 @@ static void dispatch_enqueue(struct scx_sched *sch, struct scx_dispatch_q *dsq, if (enq_flags & SCX_ENQ_CLEAR_OPSS) atomic_long_set_release(&p->scx.ops_state, SCX_OPSS_NONE); - if (is_local) { - struct rq *rq = container_of(dsq, struct rq, scx.local_dsq); - bool preempt = false; - - if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr && - rq->curr->sched_class == &ext_sched_class) { - rq->curr->scx.slice = 0; - preempt = true; - } - - if (preempt || sched_class_above(&ext_sched_class, - rq->curr->sched_class)) - resched_curr(rq); - } else { + if (is_local) + local_dsq_post_enq(dsq, p, enq_flags); + else raw_spin_unlock(&dsq->lock); - } } static void task_unlink_from_dsq(struct task_struct *p,

1 week, 4 days

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