--- /dev/null
+From 20aaa9be90b06ba600a6dafa19340497bb8ae179 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Thu, 6 Feb 2020 16:58:45 +0100
+Subject: ACPI: watchdog: Allow disabling WDAT at boot
+
+From: Jean Delvare <jdelvare@suse.de>
+
+[ Upstream commit 3f9e12e0df012c4a9a7fd7eb0d3ae69b459d6b2c ]
+
+In case the WDAT interface is broken, give the user an option to
+ignore it to let a native driver bind to the watchdog device instead.
+
+Signed-off-by: Jean Delvare <jdelvare@suse.de>
+Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
+Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ Documentation/kernel-parameters.txt | 4 ++++
+ drivers/acpi/acpi_watchdog.c | 12 +++++++++++-
+ 2 files changed, 15 insertions(+), 1 deletion(-)
+
+diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
+index b2d2f4539a3fe..e05d65d6fcb68 100644
+--- a/Documentation/kernel-parameters.txt
++++ b/Documentation/kernel-parameters.txt
+@@ -335,6 +335,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
+ dynamic table installation which will install SSDT
+ tables to /sys/firmware/acpi/tables/dynamic.
+
++ acpi_no_watchdog [HW,ACPI,WDT]
++ Ignore the ACPI-based watchdog interface (WDAT) and let
++ a native driver control the watchdog device instead.
++
+ acpi_rsdp= [ACPI,EFI,KEXEC]
+ Pass the RSDP address to the kernel, mostly used
+ on machines running EFI runtime service to boot the
+diff --git a/drivers/acpi/acpi_watchdog.c b/drivers/acpi/acpi_watchdog.c
+index 7ef0a0e105e18..4296f4932294f 100644
+--- a/drivers/acpi/acpi_watchdog.c
++++ b/drivers/acpi/acpi_watchdog.c
+@@ -58,12 +58,14 @@ static bool acpi_watchdog_uses_rtc(const struct acpi_table_wdat *wdat)
+ }
+ #endif
+
++static bool acpi_no_watchdog;
++
+ static const struct acpi_table_wdat *acpi_watchdog_get_wdat(void)
+ {
+ const struct acpi_table_wdat *wdat = NULL;
+ acpi_status status;
+
+- if (acpi_disabled)
++ if (acpi_disabled || acpi_no_watchdog)
+ return NULL;
+
+ status = acpi_get_table(ACPI_SIG_WDAT, 0,
+@@ -91,6 +93,14 @@ bool acpi_has_watchdog(void)
+ }
+ EXPORT_SYMBOL_GPL(acpi_has_watchdog);
+
++/* ACPI watchdog can be disabled on boot command line */
++static int __init disable_acpi_watchdog(char *str)
++{
++ acpi_no_watchdog = true;
++ return 1;
++}
++__setup("acpi_no_watchdog", disable_acpi_watchdog);
++
+ void __init acpi_watchdog_init(void)
+ {
+ const struct acpi_wdat_entry *entries;
+--
+2.20.1
+
--- /dev/null
+From 126a5ae6e3d67663f34cc4c3f4d8e08bbaf1d570 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Fri, 21 Feb 2020 10:44:50 +0100
+Subject: cfg80211: check reg_rule for NULL in handle_channel_custom()
+
+From: Johannes Berg <johannes.berg@intel.com>
+
+[ Upstream commit a7ee7d44b57c9ae174088e53a668852b7f4f452d ]
+
+We may end up with a NULL reg_rule after the loop in
+handle_channel_custom() if the bandwidth didn't fit,
+check if this is the case and bail out if so.
+
+Signed-off-by: Johannes Berg <johannes.berg@intel.com>
+Link: https://lore.kernel.org/r/20200221104449.3b558a50201c.I4ad3725c4dacaefd2d18d3cc65ba6d18acd5dbfe@changeid
+Signed-off-by: Johannes Berg <johannes.berg@intel.com>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ net/wireless/reg.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/net/wireless/reg.c b/net/wireless/reg.c
+index 0e66768427ba7..6d5f3f737207d 100644
+--- a/net/wireless/reg.c
++++ b/net/wireless/reg.c
+@@ -1730,7 +1730,7 @@ static void handle_channel_custom(struct wiphy *wiphy,
+ break;
+ }
+
+- if (IS_ERR(reg_rule)) {
++ if (IS_ERR_OR_NULL(reg_rule)) {
+ pr_debug("Disabling freq %d MHz as custom regd has no rule that fits it\n",
+ chan->center_freq);
+ if (wiphy->regulatory_flags & REGULATORY_WIPHY_SELF_MANAGED) {
+--
+2.20.1
+
--- /dev/null
+From 6bf9f2e1f477717e1bc28b59a7ea88cdc6d66a52 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Wed, 29 Jan 2020 17:26:31 +1100
+Subject: HID: apple: Add support for recent firmware on Magic Keyboards
+
+From: Mansour Behabadi <mansour@oxplot.com>
+
+[ Upstream commit e433be929e63265b7412478eb7ff271467aee2d7 ]
+
+Magic Keyboards with more recent firmware (0x0100) report Fn key differently.
+Without this patch, Fn key may not behave as expected and may not be
+configurable via hid_apple fnmode module parameter.
+
+Signed-off-by: Mansour Behabadi <mansour@oxplot.com>
+Signed-off-by: Jiri Kosina <jkosina@suse.cz>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ drivers/hid/hid-apple.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/drivers/hid/hid-apple.c b/drivers/hid/hid-apple.c
+index 31c087e1746d6..197eb75d10ef2 100644
+--- a/drivers/hid/hid-apple.c
++++ b/drivers/hid/hid-apple.c
+@@ -341,7 +341,8 @@ static int apple_input_mapping(struct hid_device *hdev, struct hid_input *hi,
+ unsigned long **bit, int *max)
+ {
+ if (usage->hid == (HID_UP_CUSTOM | 0x0003) ||
+- usage->hid == (HID_UP_MSVENDOR | 0x0003)) {
++ usage->hid == (HID_UP_MSVENDOR | 0x0003) ||
++ usage->hid == (HID_UP_HPVENDOR2 | 0x0003)) {
+ /* The fn key on Apple USB keyboards */
+ set_bit(EV_REP, hi->input->evbit);
+ hid_map_usage_clear(hi, usage, bit, max, EV_KEY, KEY_FN);
+--
+2.20.1
+
--- /dev/null
+From d4de12f7a1b2d637d9d96576f6dd59012d17330a Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Fri, 14 Feb 2020 14:53:07 +0800
+Subject: HID: i2c-hid: add Trekstor Surfbook E11B to descriptor override
+
+From: Kai-Heng Feng <kai.heng.feng@canonical.com>
+
+[ Upstream commit be0aba826c4a6ba5929def1962a90d6127871969 ]
+
+The Surfbook E11B uses the SIPODEV SP1064 touchpad, which does not supply
+descriptors, so it has to be added to the override list.
+
+BugLink: https://bugs.launchpad.net/bugs/1858299
+Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
+Reviewed-by: Hans de Goede <hdegoede@redhat.com>
+Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ drivers/hid/i2c-hid/i2c-hid-dmi-quirks.c | 8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+diff --git a/drivers/hid/i2c-hid/i2c-hid-dmi-quirks.c b/drivers/hid/i2c-hid/i2c-hid-dmi-quirks.c
+index 10af8585c820d..95052373a8282 100644
+--- a/drivers/hid/i2c-hid/i2c-hid-dmi-quirks.c
++++ b/drivers/hid/i2c-hid/i2c-hid-dmi-quirks.c
+@@ -341,6 +341,14 @@ static const struct dmi_system_id i2c_hid_dmi_desc_override_table[] = {
+ },
+ .driver_data = (void *)&sipodev_desc
+ },
++ {
++ .ident = "Trekstor SURFBOOK E11B",
++ .matches = {
++ DMI_EXACT_MATCH(DMI_SYS_VENDOR, "TREKSTOR"),
++ DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "SURFBOOK E11B"),
++ },
++ .driver_data = (void *)&sipodev_desc
++ },
+ {
+ .ident = "Direkt-Tek DTLAPY116-2",
+ .matches = {
+--
+2.20.1
+
--- /dev/null
+From 5c4cb92b3851495c304e904f1c10163e3bb7087f Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Fri, 21 Feb 2020 23:31:11 -0500
+Subject: jbd2: fix data races at struct journal_head
+
+From: Qian Cai <cai@lca.pw>
+
+[ Upstream commit 6c5d911249290f41f7b50b43344a7520605b1acb ]
+
+journal_head::b_transaction and journal_head::b_next_transaction could
+be accessed concurrently as noticed by KCSAN,
+
+ LTP: starting fsync04
+ /dev/zero: Can't open blockdev
+ EXT4-fs (loop0): mounting ext3 file system using the ext4 subsystem
+ EXT4-fs (loop0): mounted filesystem with ordered data mode. Opts: (null)
+ ==================================================================
+ BUG: KCSAN: data-race in __jbd2_journal_refile_buffer [jbd2] / jbd2_write_access_granted [jbd2]
+
+ write to 0xffff99f9b1bd0e30 of 8 bytes by task 25721 on cpu 70:
+ __jbd2_journal_refile_buffer+0xdd/0x210 [jbd2]
+ __jbd2_journal_refile_buffer at fs/jbd2/transaction.c:2569
+ jbd2_journal_commit_transaction+0x2d15/0x3f20 [jbd2]
+ (inlined by) jbd2_journal_commit_transaction at fs/jbd2/commit.c:1034
+ kjournald2+0x13b/0x450 [jbd2]
+ kthread+0x1cd/0x1f0
+ ret_from_fork+0x27/0x50
+
+ read to 0xffff99f9b1bd0e30 of 8 bytes by task 25724 on cpu 68:
+ jbd2_write_access_granted+0x1b2/0x250 [jbd2]
+ jbd2_write_access_granted at fs/jbd2/transaction.c:1155
+ jbd2_journal_get_write_access+0x2c/0x60 [jbd2]
+ __ext4_journal_get_write_access+0x50/0x90 [ext4]
+ ext4_mb_mark_diskspace_used+0x158/0x620 [ext4]
+ ext4_mb_new_blocks+0x54f/0xca0 [ext4]
+ ext4_ind_map_blocks+0xc79/0x1b40 [ext4]
+ ext4_map_blocks+0x3b4/0x950 [ext4]
+ _ext4_get_block+0xfc/0x270 [ext4]
+ ext4_get_block+0x3b/0x50 [ext4]
+ __block_write_begin_int+0x22e/0xae0
+ __block_write_begin+0x39/0x50
+ ext4_write_begin+0x388/0xb50 [ext4]
+ generic_perform_write+0x15d/0x290
+ ext4_buffered_write_iter+0x11f/0x210 [ext4]
+ ext4_file_write_iter+0xce/0x9e0 [ext4]
+ new_sync_write+0x29c/0x3b0
+ __vfs_write+0x92/0xa0
+ vfs_write+0x103/0x260
+ ksys_write+0x9d/0x130
+ __x64_sys_write+0x4c/0x60
+ do_syscall_64+0x91/0xb05
+ entry_SYSCALL_64_after_hwframe+0x49/0xbe
+
+ 5 locks held by fsync04/25724:
+ #0: ffff99f9911093f8 (sb_writers#13){.+.+}, at: vfs_write+0x21c/0x260
+ #1: ffff99f9db4c0348 (&sb->s_type->i_mutex_key#15){+.+.}, at: ext4_buffered_write_iter+0x65/0x210 [ext4]
+ #2: ffff99f5e7dfcf58 (jbd2_handle){++++}, at: start_this_handle+0x1c1/0x9d0 [jbd2]
+ #3: ffff99f9db4c0168 (&ei->i_data_sem){++++}, at: ext4_map_blocks+0x176/0x950 [ext4]
+ #4: ffffffff99086b40 (rcu_read_lock){....}, at: jbd2_write_access_granted+0x4e/0x250 [jbd2]
+ irq event stamp: 1407125
+ hardirqs last enabled at (1407125): [<ffffffff980da9b7>] __find_get_block+0x107/0x790
+ hardirqs last disabled at (1407124): [<ffffffff980da8f9>] __find_get_block+0x49/0x790
+ softirqs last enabled at (1405528): [<ffffffff98a0034c>] __do_softirq+0x34c/0x57c
+ softirqs last disabled at (1405521): [<ffffffff97cc67a2>] irq_exit+0xa2/0xc0
+
+ Reported by Kernel Concurrency Sanitizer on:
+ CPU: 68 PID: 25724 Comm: fsync04 Tainted: G L 5.6.0-rc2-next-20200221+ #7
+ Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
+
+The plain reads are outside of jh->b_state_lock critical section which result
+in data races. Fix them by adding pairs of READ|WRITE_ONCE().
+
+Reviewed-by: Jan Kara <jack@suse.cz>
+Signed-off-by: Qian Cai <cai@lca.pw>
+Link: https://lore.kernel.org/r/20200222043111.2227-1-cai@lca.pw
+Signed-off-by: Theodore Ts'o <tytso@mit.edu>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ fs/jbd2/transaction.c | 8 ++++----
+ 1 file changed, 4 insertions(+), 4 deletions(-)
+
+diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
+index 04dd0652bb5ca..8de458d64134a 100644
+--- a/fs/jbd2/transaction.c
++++ b/fs/jbd2/transaction.c
+@@ -1037,8 +1037,8 @@ static bool jbd2_write_access_granted(handle_t *handle, struct buffer_head *bh,
+ /* For undo access buffer must have data copied */
+ if (undo && !jh->b_committed_data)
+ goto out;
+- if (jh->b_transaction != handle->h_transaction &&
+- jh->b_next_transaction != handle->h_transaction)
++ if (READ_ONCE(jh->b_transaction) != handle->h_transaction &&
++ READ_ONCE(jh->b_next_transaction) != handle->h_transaction)
+ goto out;
+ /*
+ * There are two reasons for the barrier here:
+@@ -2448,8 +2448,8 @@ void __jbd2_journal_refile_buffer(struct journal_head *jh)
+ * our jh reference and thus __jbd2_journal_file_buffer() must not
+ * take a new one.
+ */
+- jh->b_transaction = jh->b_next_transaction;
+- jh->b_next_transaction = NULL;
++ WRITE_ONCE(jh->b_transaction, jh->b_next_transaction);
++ WRITE_ONCE(jh->b_next_transaction, NULL);
+ if (buffer_freed(bh))
+ jlist = BJ_Forget;
+ else if (jh->b_modified)
+--
+2.20.1
+
--- /dev/null
+From 82c652c6b3a10cb942e05f8c685a1c972bf4b205 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Sun, 23 Feb 2020 20:03:02 +0530
+Subject: mac80211: rx: avoid RCU list traversal under mutex
+
+From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
+
+[ Upstream commit 253216ffb2a002a682c6f68bd3adff5b98b71de8 ]
+
+local->sta_mtx is held in __ieee80211_check_fast_rx_iface().
+No need to use list_for_each_entry_rcu() as it also requires
+a cond argument to avoid false lockdep warnings when not used in
+RCU read-side section (with CONFIG_PROVE_RCU_LIST).
+Therefore use list_for_each_entry();
+
+Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
+Link: https://lore.kernel.org/r/20200223143302.15390-1-madhuparnabhowmik10@gmail.com
+Signed-off-by: Johannes Berg <johannes.berg@intel.com>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ net/mac80211/rx.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
+index 74652eb2f90fd..a6f265262f151 100644
+--- a/net/mac80211/rx.c
++++ b/net/mac80211/rx.c
+@@ -3841,7 +3841,7 @@ void __ieee80211_check_fast_rx_iface(struct ieee80211_sub_if_data *sdata)
+
+ lockdep_assert_held(&local->sta_mtx);
+
+- list_for_each_entry_rcu(sta, &local->sta_list, list) {
++ list_for_each_entry(sta, &local->sta_list, list) {
+ if (sdata != sta->sdata &&
+ (!sta->sdata->bss || sta->sdata->bss != sdata->bss))
+ continue;
+--
+2.20.1
+
--- /dev/null
+From a9a9a55f2513e1586879ca901c507aaf06345024 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Sun, 23 Feb 2020 14:38:40 +0100
+Subject: net: ks8851-ml: Fix IRQ handling and locking
+
+From: Marek Vasut <marex@denx.de>
+
+[ Upstream commit 44343418d0f2f623cb9da6f5000df793131cbe3b ]
+
+The KS8851 requires that packet RX and TX are mutually exclusive.
+Currently, the driver hopes to achieve this by disabling interrupt
+from the card by writing the card registers and by disabling the
+interrupt on the interrupt controller. This however is racy on SMP.
+
+Replace this approach by expanding the spinlock used around the
+ks_start_xmit() TX path to ks_irq() RX path to assure true mutual
+exclusion and remove the interrupt enabling/disabling, which is
+now not needed anymore. Furthermore, disable interrupts also in
+ks_net_stop(), which was missing before.
+
+Note that a massive improvement here would be to re-use the KS8851
+driver approach, which is to move the TX path into a worker thread,
+interrupt handling to threaded interrupt, and synchronize everything
+with mutexes, but that would be a much bigger rework, for a separate
+patch.
+
+Signed-off-by: Marek Vasut <marex@denx.de>
+Cc: David S. Miller <davem@davemloft.net>
+Cc: Lukas Wunner <lukas@wunner.de>
+Cc: Petr Stetiar <ynezz@true.cz>
+Cc: YueHaibing <yuehaibing@huawei.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ drivers/net/ethernet/micrel/ks8851_mll.c | 14 ++++++++------
+ 1 file changed, 8 insertions(+), 6 deletions(-)
+
+diff --git a/drivers/net/ethernet/micrel/ks8851_mll.c b/drivers/net/ethernet/micrel/ks8851_mll.c
+index d94e151cff12b..d4747caf1e7cc 100644
+--- a/drivers/net/ethernet/micrel/ks8851_mll.c
++++ b/drivers/net/ethernet/micrel/ks8851_mll.c
+@@ -831,14 +831,17 @@ static irqreturn_t ks_irq(int irq, void *pw)
+ {
+ struct net_device *netdev = pw;
+ struct ks_net *ks = netdev_priv(netdev);
++ unsigned long flags;
+ u16 status;
+
++ spin_lock_irqsave(&ks->statelock, flags);
+ /*this should be the first in IRQ handler */
+ ks_save_cmd_reg(ks);
+
+ status = ks_rdreg16(ks, KS_ISR);
+ if (unlikely(!status)) {
+ ks_restore_cmd_reg(ks);
++ spin_unlock_irqrestore(&ks->statelock, flags);
+ return IRQ_NONE;
+ }
+
+@@ -864,6 +867,7 @@ static irqreturn_t ks_irq(int irq, void *pw)
+ ks->netdev->stats.rx_over_errors++;
+ /* this should be the last in IRQ handler*/
+ ks_restore_cmd_reg(ks);
++ spin_unlock_irqrestore(&ks->statelock, flags);
+ return IRQ_HANDLED;
+ }
+
+@@ -933,6 +937,7 @@ static int ks_net_stop(struct net_device *netdev)
+
+ /* shutdown RX/TX QMU */
+ ks_disable_qmu(ks);
++ ks_disable_int(ks);
+
+ /* set powermode to soft power down to save power */
+ ks_set_powermode(ks, PMECR_PM_SOFTDOWN);
+@@ -989,10 +994,9 @@ static netdev_tx_t ks_start_xmit(struct sk_buff *skb, struct net_device *netdev)
+ {
+ netdev_tx_t retv = NETDEV_TX_OK;
+ struct ks_net *ks = netdev_priv(netdev);
++ unsigned long flags;
+
+- disable_irq(netdev->irq);
+- ks_disable_int(ks);
+- spin_lock(&ks->statelock);
++ spin_lock_irqsave(&ks->statelock, flags);
+
+ /* Extra space are required:
+ * 4 byte for alignment, 4 for status/length, 4 for CRC
+@@ -1006,9 +1010,7 @@ static netdev_tx_t ks_start_xmit(struct sk_buff *skb, struct net_device *netdev)
+ dev_kfree_skb(skb);
+ } else
+ retv = NETDEV_TX_BUSY;
+- spin_unlock(&ks->statelock);
+- ks_enable_int(ks);
+- enable_irq(netdev->irq);
++ spin_unlock_irqrestore(&ks->statelock, flags);
+ return retv;
+ }
+
+--
+2.20.1
+
batman-adv-avoid-probe-elp-information-leak.patch
batman-adv-use-explicit-tvlv-padding-for-elp-packets.patch
perf-amd-uncore-replace-manual-sampling-check-with-c.patch
+acpi-watchdog-allow-disabling-wdat-at-boot.patch
+hid-apple-add-support-for-recent-firmware-on-magic-k.patch
+hid-i2c-hid-add-trekstor-surfbook-e11b-to-descriptor.patch
+cfg80211-check-reg_rule-for-null-in-handle_channel_c.patch
+net-ks8851-ml-fix-irq-handling-and-locking.patch
+mac80211-rx-avoid-rcu-list-traversal-under-mutex.patch
+signal-avoid-double-atomic-counter-increments-for-us.patch
+jbd2-fix-data-races-at-struct-journal_head.patch
--- /dev/null
+From c17bb196d4ddeaa73e0f23872f9eeebaec9ba20b Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Mon, 24 Feb 2020 12:47:14 -0800
+Subject: signal: avoid double atomic counter increments for user accounting
+
+From: Linus Torvalds <torvalds@linux-foundation.org>
+
+[ Upstream commit fda31c50292a5062332fa0343c084bd9f46604d9 ]
+
+When queueing a signal, we increment both the users count of pending
+signals (for RLIMIT_SIGPENDING tracking) and we increment the refcount
+of the user struct itself (because we keep a reference to the user in
+the signal structure in order to correctly account for it when freeing).
+
+That turns out to be fairly expensive, because both of them are atomic
+updates, and particularly under extreme signal handling pressure on big
+machines, you can get a lot of cache contention on the user struct.
+That can then cause horrid cacheline ping-pong when you do these
+multiple accesses.
+
+So change the reference counting to only pin the user for the _first_
+pending signal, and to unpin it when the last pending signal is
+dequeued. That means that when a user sees a lot of concurrent signal
+queuing - which is the only situation when this matters - the only
+atomic access needed is generally the 'sigpending' count update.
+
+This was noticed because of a particularly odd timing artifact on a
+dual-socket 96C/192T Cascade Lake platform: when you get into bad
+contention, on that machine for some reason seems to be much worse when
+the contention happens in the upper 32-byte half of the cacheline.
+
+As a result, the kernel test robot will-it-scale 'signal1' benchmark had
+an odd performance regression simply due to random alignment of the
+'struct user_struct' (and pointed to a completely unrelated and
+apparently nonsensical commit for the regression).
+
+Avoiding the double increments (and decrements on the dequeueing side,
+of course) makes for much less contention and hugely improved
+performance on that will-it-scale microbenchmark.
+
+Quoting Feng Tang:
+
+ "It makes a big difference, that the performance score is tripled! bump
+ from original 17000 to 54000. Also the gap between 5.0-rc6 and
+ 5.0-rc6+Jiri's patch is reduced to around 2%"
+
+[ The "2% gap" is the odd cacheline placement difference on that
+ platform: under the extreme contention case, the effect of which half
+ of the cacheline was hot was 5%, so with the reduced contention the
+ odd timing artifact is reduced too ]
+
+It does help in the non-contended case too, but is not nearly as
+noticeable.
+
+Reported-and-tested-by: Feng Tang <feng.tang@intel.com>
+Cc: Eric W. Biederman <ebiederm@xmission.com>
+Cc: Huang, Ying <ying.huang@intel.com>
+Cc: Philip Li <philip.li@intel.com>
+Cc: Andi Kleen <andi.kleen@intel.com>
+Cc: Jiri Olsa <jolsa@redhat.com>
+Cc: Peter Zijlstra <peterz@infradead.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ kernel/signal.c | 23 ++++++++++++++---------
+ 1 file changed, 14 insertions(+), 9 deletions(-)
+
+diff --git a/kernel/signal.c b/kernel/signal.c
+index 57fadbe69c2e6..d90ccbeb909d2 100644
+--- a/kernel/signal.c
++++ b/kernel/signal.c
+@@ -373,27 +373,32 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimi
+ {
+ struct sigqueue *q = NULL;
+ struct user_struct *user;
++ int sigpending;
+
+ /*
+ * Protect access to @t credentials. This can go away when all
+ * callers hold rcu read lock.
++ *
++ * NOTE! A pending signal will hold on to the user refcount,
++ * and we get/put the refcount only when the sigpending count
++ * changes from/to zero.
+ */
+ rcu_read_lock();
+- user = get_uid(__task_cred(t)->user);
+- atomic_inc(&user->sigpending);
++ user = __task_cred(t)->user;
++ sigpending = atomic_inc_return(&user->sigpending);
++ if (sigpending == 1)
++ get_uid(user);
+ rcu_read_unlock();
+
+- if (override_rlimit ||
+- atomic_read(&user->sigpending) <=
+- task_rlimit(t, RLIMIT_SIGPENDING)) {
++ if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {
+ q = kmem_cache_alloc(sigqueue_cachep, flags);
+ } else {
+ print_dropped_signal(sig);
+ }
+
+ if (unlikely(q == NULL)) {
+- atomic_dec(&user->sigpending);
+- free_uid(user);
++ if (atomic_dec_and_test(&user->sigpending))
++ free_uid(user);
+ } else {
+ INIT_LIST_HEAD(&q->list);
+ q->flags = 0;
+@@ -407,8 +412,8 @@ static void __sigqueue_free(struct sigqueue *q)
+ {
+ if (q->flags & SIGQUEUE_PREALLOC)
+ return;
+- atomic_dec(&q->user->sigpending);
+- free_uid(q->user);
++ if (atomic_dec_and_test(&q->user->sigpending))
++ free_uid(q->user);
+ kmem_cache_free(sigqueue_cachep, q);
+ }
+
+--
+2.20.1
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
