July 2018 - Linux-stable-mirror

[PATCH v4 2/2] block: Ensure that a request queue is dissociated from the cgroup controller

by Bart Van Assche

Several block drivers call alloc_disk() followed by put_disk() if something fails before device_add_disk() is called without calling blk_cleanup_queue(). Make sure that also for this scenario a request queue is dissociated from the cgroup controller. This patch avoids that loading the parport_pc, paride and pf drivers triggers the following kernel crash: BUG: KASAN: null-ptr-deref in pi_init+0x42e/0x580 [paride] Read of size 4 at addr 0000000000000008 by task modprobe/744 Call Trace: dump_stack+0x9a/0xeb kasan_report+0x139/0x350 pi_init+0x42e/0x580 [paride] pf_init+0x2bb/0x1000 [pf] do_one_initcall+0x8e/0x405 do_init_module+0xd9/0x2f2 load_module+0x3ab4/0x4700 SYSC_finit_module+0x176/0x1a0 do_syscall_64+0xee/0x2b0 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Reported-by: Alexandru Moise <00moses.alexander00(a)gmail.com> Fixes: a063057d7c73 ("block: Fix a race between request queue removal and the block cgroup controller") # v4.17 Signed-off-by: Bart Van Assche <bart.vanassche(a)wdc.com> Tested-by: Alexandru Moise <00moses.alexander00(a)gmail.com> Cc: Tejun Heo <tj(a)kernel.org> Cc: Christoph Hellwig <hch(a)lst.de> Cc: Ming Lei <ming.lei(a)redhat.com> Cc: Johannes Thumshirn <jthumshirn(a)suse.de> Cc: Alexandru Moise <00moses.alexander00(a)gmail.com> Cc: Joseph Qi <joseph.qi(a)linux.alibaba.com> Cc: <stable(a)vger.kernel.org> --- block/blk-sysfs.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index ca1984ecbdeb..26275d9babcb 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -802,6 +802,31 @@ static void __blk_release_queue(struct work_struct *work) blk_stat_remove_callback(q, q->poll_cb); blk_stat_free_callback(q->poll_cb); + if (!blk_queue_dead(q)) { + /* + * Last reference was dropped without having called + * blk_cleanup_queue(). + */ + WARN_ONCE(blk_queue_init_done(q), + "request queue %p has been registered but blk_cleanup_queue() has not been called for that queue\n", + q); + blk_exit_queue(q); + } + +#ifdef CONFIG_BLK_CGROUP + { + struct blkcg_gq *blkg; + + rcu_read_lock(); + blkg = blkg_lookup(&blkcg_root, q); + rcu_read_unlock(); + + WARN(blkg, + "request queue %p is being released but it has not yet been removed from the blkcg controller\n", + q); + } +#endif + blk_free_queue_stats(q->stats); blk_exit_rl(q, &q->root_rl); -- 2.18.0

5 years, 8 months

4
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[PATCH v6 0/8] powerpc/pseries: Machine check handler improvements.

by Mahesh J Salgaonkar

This patch series includes some improvement to Machine check handler for pSeries. Patch 1 fixes a buffer overrun issue if rtas extended error log size is greater than RTAS_ERROR_LOG_MAX. Patch 2 fixes an issue where machine check handler crashes kernel while accessing vmalloc-ed buffer while in nmi context. Patch 3 fixes endain bug while restoring of r3 in MCE handler. Patch 5 implements a real mode mce handler and flushes the SLBs on SLB error. Patch 6 display's the MCE error details on console. Patch 7 saves and dumps the SLB contents on SLB MCE errors to improve the debugability. Patch 8 consolidates mce early real mode handling code. Change in V6: - Introduce patch 8 to consolidate early real mode handling code. - Address Nick's comment on erroneous hunk. Change in V5: - Use min_t instead of max_t. - Fix an issue reported by kbuild test robot and address review comments. Change in V4: - Flush the SLBs in real mode mce handler to handle SLB errors for entry 0. - Allocate buffers per cpu to hold rtas error log and old slb contents. - Defer the logging of rtas error log to irq work queue. Change in V3: - Moved patch 5 to patch 2 Change in V2: - patch 3: Display additional info (NIP and task info) in MCE error details. - patch 5: Fix endain bug while restoring of r3 in MCE handler. --- Mahesh Salgaonkar (8): powerpc/pseries: Avoid using the size greater than RTAS_ERROR_LOG_MAX. powerpc/pseries: Defer the logging of rtas error to irq work queue. powerpc/pseries: Fix endainness while restoring of r3 in MCE handler. powerpc/pseries: Define MCE error event section. powerpc/pseries: flush SLB contents on SLB MCE errors. powerpc/pseries: Display machine check error details. powerpc/pseries: Dump the SLB contents on SLB MCE errors. powernv/pseries: consolidate code for mce early handling. arch/powerpc/include/asm/book3s/64/mmu-hash.h | 8 + arch/powerpc/include/asm/machdep.h | 1 arch/powerpc/include/asm/paca.h | 4 arch/powerpc/include/asm/rtas.h | 116 ++++++++++++ arch/powerpc/kernel/exceptions-64s.S | 18 +- arch/powerpc/kernel/mce.c | 16 +- arch/powerpc/mm/slb.c | 63 +++++++ arch/powerpc/platforms/pseries/pseries.h | 1 arch/powerpc/platforms/pseries/ras.c | 242 +++++++++++++++++++++++-- arch/powerpc/platforms/pseries/setup.c | 27 +++ 10 files changed, 471 insertions(+), 25 deletions(-) -- Signature

5 years, 8 months

2
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[PATCH v4 1/2] block: Introduce blk_exit_queue()

by Bart Van Assche

This patch does not change any functionality. Signed-off-by: Bart Van Assche <bart.vanassche(a)wdc.com> Cc: Christoph Hellwig <hch(a)lst.de> Cc: Ming Lei <ming.lei(a)redhat.com> Cc: Omar Sandoval <osandov(a)fb.com> Cc: Johannes Thumshirn <jthumshirn(a)suse.de> Cc: Alexandru Moise <00moses.alexander00(a)gmail.com> Cc: Joseph Qi <joseph.qi(a)linux.alibaba.com> Cc: <stable(a)vger.kernel.org> --- block/blk-core.c | 54 +++++++++++++++++++++++++++--------------------- block/blk.h | 1 + 2 files changed, 31 insertions(+), 24 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 7c65e297a4f1..5fbfa8484c95 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -719,6 +719,35 @@ void blk_set_queue_dying(struct request_queue *q) } EXPORT_SYMBOL_GPL(blk_set_queue_dying); +/* Unconfigure the I/O scheduler and dissociate from the cgroup controller. */ +void blk_exit_queue(struct request_queue *q) +{ + /* + * Since the I/O scheduler exit code may access cgroup information, + * perform I/O scheduler exit before disassociating from the block + * cgroup controller. + */ + if (q->elevator) { + ioc_clear_queue(q); + elevator_exit(q, q->elevator); + q->elevator = NULL; + } + + /* + * Remove all references to @q from the block cgroup controller before + * restoring @q->queue_lock to avoid that restoring this pointer causes + * e.g. blkcg_print_blkgs() to crash. + */ + blkcg_exit_queue(q); + + /* + * Since the cgroup code may dereference the @q->backing_dev_info + * pointer, only decrease its reference count after having removed the + * association with the block cgroup controller. + */ + bdi_put(q->backing_dev_info); +} + /** * blk_cleanup_queue - shutdown a request queue * @q: request queue to shutdown @@ -788,30 +817,7 @@ void blk_cleanup_queue(struct request_queue *q) */ WARN_ON_ONCE(q->kobj.state_in_sysfs); - /* - * Since the I/O scheduler exit code may access cgroup information, - * perform I/O scheduler exit before disassociating from the block - * cgroup controller. - */ - if (q->elevator) { - ioc_clear_queue(q); - elevator_exit(q, q->elevator); - q->elevator = NULL; - } - - /* - * Remove all references to @q from the block cgroup controller before - * restoring @q->queue_lock to avoid that restoring this pointer causes - * e.g. blkcg_print_blkgs() to crash. - */ - blkcg_exit_queue(q); - - /* - * Since the cgroup code may dereference the @q->backing_dev_info - * pointer, only decrease its reference count after having removed the - * association with the block cgroup controller. - */ - bdi_put(q->backing_dev_info); + blk_exit_queue(q); if (q->mq_ops) blk_mq_free_queue(q); diff --git a/block/blk.h b/block/blk.h index 6adae8f94279..aeb8026f4d7b 100644 --- a/block/blk.h +++ b/block/blk.h @@ -130,6 +130,7 @@ void blk_free_flush_queue(struct blk_flush_queue *q); int blk_init_rl(struct request_list *rl, struct request_queue *q, gfp_t gfp_mask); void blk_exit_rl(struct request_queue *q, struct request_list *rl); +void blk_exit_queue(struct request_queue *q); void blk_rq_bio_prep(struct request_queue *q, struct request *rq, struct bio *bio); void blk_queue_bypass_start(struct request_queue *q); -- 2.18.0

5 years, 8 months

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FAILED: patch "[PATCH] Btrfs: fix file data corruption after cloning a range and" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-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>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From bd3599a0e142cd73edd3b6801068ac3f48ac771a Mon Sep 17 00:00:00 2001 From: Filipe Manana <fdmanana(a)suse.com> Date: Thu, 12 Jul 2018 01:36:43 +0100 Subject: [PATCH] Btrfs: fix file data corruption after cloning a range and fsync When we clone a range into a file we can end up dropping existing extent maps (or trimming them) and replacing them with new ones if the range to be cloned overlaps with a range in the destination inode. When that happens we add the new extent maps to the list of modified extents in the inode's extent map tree, so that a "fast" fsync (the flag BTRFS_INODE_NEEDS_FULL_SYNC not set in the inode) will see the extent maps and log corresponding extent items. However, at the end of range cloning operation we do truncate all the pages in the affected range (in order to ensure future reads will not get stale data). Sometimes this truncation will release the corresponding extent maps besides the pages from the page cache. If this happens, then a "fast" fsync operation will miss logging some extent items, because it relies exclusively on the extent maps being present in the inode's extent tree, leading to data loss/corruption if the fsync ends up using the same transaction used by the clone operation (that transaction was not committed in the meanwhile). An extent map is released through the callback btrfs_invalidatepage(), which gets called by truncate_inode_pages_range(), and it calls __btrfs_releasepage(). The later ends up calling try_release_extent_mapping() which will release the extent map if some conditions are met, like the file size being greater than 16Mb, gfp flags allow blocking and the range not being locked (which is the case during the clone operation) nor being the extent map flagged as pinned (also the case for cloning). The following example, turned into a test for fstests, reproduces the issue: $ mkfs.btrfs -f /dev/sdb $ mount /dev/sdb /mnt $ xfs_io -f -c "pwrite -S 0x18 9000K 6908K" /mnt/foo $ xfs_io -f -c "pwrite -S 0x20 2572K 156K" /mnt/bar $ xfs_io -c "fsync" /mnt/bar # reflink destination offset corresponds to the size of file bar, # 2728Kb minus 4Kb. $ xfs_io -c ""reflink ${SCRATCH_MNT}/foo 0 2724K 15908K" /mnt/bar $ xfs_io -c "fsync" /mnt/bar $ md5sum /mnt/bar 95a95813a8c2abc9aa75a6c2914a077e /mnt/bar <power fail> $ mount /dev/sdb /mnt $ md5sum /mnt/bar 207fd8d0b161be8a84b945f0df8d5f8d /mnt/bar # digest should be 95a95813a8c2abc9aa75a6c2914a077e like before the # power failure In the above example, the destination offset of the clone operation corresponds to the size of the "bar" file minus 4Kb. So during the clone operation, the extent map covering the range from 2572Kb to 2728Kb gets trimmed so that it ends at offset 2724Kb, and a new extent map covering the range from 2724Kb to 11724Kb is created. So at the end of the clone operation when we ask to truncate the pages in the range from 2724Kb to 2724Kb + 15908Kb, the page invalidation callback ends up removing the new extent map (through try_release_extent_mapping()) when the page at offset 2724Kb is passed to that callback. Fix this by setting the bit BTRFS_INODE_NEEDS_FULL_SYNC whenever an extent map is removed at try_release_extent_mapping(), forcing the next fsync to search for modified extents in the fs/subvolume tree instead of relying on the presence of extent maps in memory. This way we can continue doing a "fast" fsync if the destination range of a clone operation does not overlap with an existing range or if any of the criteria necessary to remove an extent map at try_release_extent_mapping() is not met (file size not bigger then 16Mb or gfp flags do not allow blocking). CC: stable(a)vger.kernel.org # 3.16+ Signed-off-by: Filipe Manana <fdmanana(a)suse.com> Signed-off-by: David Sterba <dsterba(a)suse.com> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 1aa91d57404a..8fd86e29085f 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4241,8 +4241,9 @@ int try_release_extent_mapping(struct page *page, gfp_t mask) struct extent_map *em; u64 start = page_offset(page); u64 end = start + PAGE_SIZE - 1; - struct extent_io_tree *tree = &BTRFS_I(page->mapping->host)->io_tree; - struct extent_map_tree *map = &BTRFS_I(page->mapping->host)->extent_tree; + struct btrfs_inode *btrfs_inode = BTRFS_I(page->mapping->host); + struct extent_io_tree *tree = &btrfs_inode->io_tree; + struct extent_map_tree *map = &btrfs_inode->extent_tree; if (gfpflags_allow_blocking(mask) && page->mapping->host->i_size > SZ_16M) { @@ -4265,6 +4266,8 @@ int try_release_extent_mapping(struct page *page, gfp_t mask) extent_map_end(em) - 1, EXTENT_LOCKED | EXTENT_WRITEBACK, 0, NULL)) { + set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, + &btrfs_inode->runtime_flags); remove_extent_mapping(map, em); /* once for the rb tree */ free_extent_map(em);

5 years, 8 months

3
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FAILED: patch "[PATCH] i2c: imx: Fix reinit_completion() use" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-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>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9f9e3e0d4dd3338b3f3dde080789f71901e1e4ff Mon Sep 17 00:00:00 2001 From: Esben Haabendal <eha(a)deif.com> Date: Mon, 9 Jul 2018 11:43:01 +0200 Subject: [PATCH] i2c: imx: Fix reinit_completion() use MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Make sure to call reinit_completion() before dma is started to avoid race condition where reinit_completion() is called after complete() and before wait_for_completion_timeout(). Signed-off-by: Esben Haabendal <eha(a)deif.com> Fixes: ce1a78840ff7 ("i2c: imx: add DMA support for freescale i2c driver") Reviewed-by: Uwe Kleine-König <u.kleine-koenig(a)pengutronix.de> Signed-off-by: Wolfram Sang <wsa(a)the-dreams.de> Cc: stable(a)kernel.org diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c index 0207e194f84b..39cfd98c7b23 100644 --- a/drivers/i2c/busses/i2c-imx.c +++ b/drivers/i2c/busses/i2c-imx.c @@ -368,6 +368,7 @@ static int i2c_imx_dma_xfer(struct imx_i2c_struct *i2c_imx, goto err_desc; } + reinit_completion(&dma->cmd_complete); txdesc->callback = i2c_imx_dma_callback; txdesc->callback_param = i2c_imx; if (dma_submit_error(dmaengine_submit(txdesc))) { @@ -622,7 +623,6 @@ static int i2c_imx_dma_write(struct imx_i2c_struct *i2c_imx, * The first byte must be transmitted by the CPU. */ imx_i2c_write_reg(i2c_8bit_addr_from_msg(msgs), i2c_imx, IMX_I2C_I2DR); - reinit_completion(&i2c_imx->dma->cmd_complete); time_left = wait_for_completion_timeout( &i2c_imx->dma->cmd_complete, msecs_to_jiffies(DMA_TIMEOUT)); @@ -681,7 +681,6 @@ static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx, if (result) return result; - reinit_completion(&i2c_imx->dma->cmd_complete); time_left = wait_for_completion_timeout( &i2c_imx->dma->cmd_complete, msecs_to_jiffies(DMA_TIMEOUT));

5 years, 8 months

3
2
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FAILED: patch "[PATCH] ring_buffer: tracing: Inherit the tracing setting to next" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-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>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 73c8d8945505acdcbae137c2e00a1232e0be709f Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu <mhiramat(a)kernel.org> Date: Sat, 14 Jul 2018 01:28:15 +0900 Subject: [PATCH] ring_buffer: tracing: Inherit the tracing setting to next ring buffer Maintain the tracing on/off setting of the ring_buffer when switching to the trace buffer snapshot. Taking a snapshot is done by swapping the backup ring buffer (max_tr_buffer). But since the tracing on/off setting is defined by the ring buffer, when swapping it, the tracing on/off setting can also be changed. This causes a strange result like below: /sys/kernel/debug/tracing # cat tracing_on 1 /sys/kernel/debug/tracing # echo 0 > tracing_on /sys/kernel/debug/tracing # cat tracing_on 0 /sys/kernel/debug/tracing # echo 1 > snapshot /sys/kernel/debug/tracing # cat tracing_on 1 /sys/kernel/debug/tracing # echo 1 > snapshot /sys/kernel/debug/tracing # cat tracing_on 0 We don't touch tracing_on, but snapshot changes tracing_on setting each time. This is an anomaly, because user doesn't know that each "ring_buffer" stores its own tracing-enable state and the snapshot is done by swapping ring buffers. Link: http://lkml.kernel.org/r/153149929558.11274.11730609978254724394.stgit@devb… Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Tom Zanussi <tom.zanussi(a)linux.intel.com> Cc: Hiraku Toyooka <hiraku.toyooka(a)cybertrust.co.jp> Cc: stable(a)vger.kernel.org Fixes: debdd57f5145 ("tracing: Make a snapshot feature available from userspace") Signed-off-by: Masami Hiramatsu <mhiramat(a)kernel.org> [ Updated commit log and comment in the code ] Signed-off-by: Steven Rostedt (VMware) <rostedt(a)goodmis.org> diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index b72ebdff0b77..003d09ab308d 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -165,6 +165,7 @@ void ring_buffer_record_enable(struct ring_buffer *buffer); void ring_buffer_record_off(struct ring_buffer *buffer); void ring_buffer_record_on(struct ring_buffer *buffer); int ring_buffer_record_is_on(struct ring_buffer *buffer); +int ring_buffer_record_is_set_on(struct ring_buffer *buffer); void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu); void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu); diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 6a46af21765c..0b0b688ea166 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3226,6 +3226,22 @@ int ring_buffer_record_is_on(struct ring_buffer *buffer) return !atomic_read(&buffer->record_disabled); } +/** + * ring_buffer_record_is_set_on - return true if the ring buffer is set writable + * @buffer: The ring buffer to see if write is set enabled + * + * Returns true if the ring buffer is set writable by ring_buffer_record_on(). + * Note that this does NOT mean it is in a writable state. + * + * It may return true when the ring buffer has been disabled by + * ring_buffer_record_disable(), as that is a temporary disabling of + * the ring buffer. + */ +int ring_buffer_record_is_set_on(struct ring_buffer *buffer) +{ + return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); +} + /** * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer * @buffer: The ring buffer to stop writes to. diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 87cf25171fb8..823687997b01 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1373,6 +1373,12 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu) arch_spin_lock(&tr->max_lock); + /* Inherit the recordable setting from trace_buffer */ + if (ring_buffer_record_is_set_on(tr->trace_buffer.buffer)) + ring_buffer_record_on(tr->max_buffer.buffer); + else + ring_buffer_record_off(tr->max_buffer.buffer); + swap(tr->trace_buffer.buffer, tr->max_buffer.buffer); __update_max_tr(tr, tsk, cpu);

5 years, 8 months

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FAILED: patch "[PATCH] ext4: fix false negatives *and* false positives in" failed to apply to 4.14-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 4.14-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>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 44de022c4382541cebdd6de4465d1f4f465ff1dd Mon Sep 17 00:00:00 2001 From: Theodore Ts'o <tytso(a)mit.edu> Date: Sun, 8 Jul 2018 19:35:02 -0400 Subject: [PATCH] ext4: fix false negatives *and* false positives in ext4_check_descriptors() Ext4_check_descriptors() was getting called before s_gdb_count was initialized. So for file systems w/o the meta_bg feature, allocation bitmaps could overlap the block group descriptors and ext4 wouldn't notice. For file systems with the meta_bg feature enabled, there was a fencepost error which would cause the ext4_check_descriptors() to incorrectly believe that the block allocation bitmap overlaps with the block group descriptor blocks, and it would reject the mount. Fix both of these problems. Signed-off-by: Theodore Ts'o <tytso(a)mit.edu> Cc: stable(a)vger.kernel.org diff --git a/fs/ext4/super.c b/fs/ext4/super.c index ba2396a7bd04..eff5c983e067 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2342,7 +2342,7 @@ static int ext4_check_descriptors(struct super_block *sb, struct ext4_sb_info *sbi = EXT4_SB(sb); ext4_fsblk_t first_block = le32_to_cpu(sbi->s_es->s_first_data_block); ext4_fsblk_t last_block; - ext4_fsblk_t last_bg_block = sb_block + ext4_bg_num_gdb(sb, 0) + 1; + ext4_fsblk_t last_bg_block = sb_block + ext4_bg_num_gdb(sb, 0); ext4_fsblk_t block_bitmap; ext4_fsblk_t inode_bitmap; ext4_fsblk_t inode_table; @@ -4085,14 +4085,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) goto failed_mount2; } } + sbi->s_gdb_count = db_count; if (!ext4_check_descriptors(sb, logical_sb_block, &first_not_zeroed)) { ext4_msg(sb, KERN_ERR, "group descriptors corrupted!"); ret = -EFSCORRUPTED; goto failed_mount2; } - sbi->s_gdb_count = db_count; - timer_setup(&sbi->s_err_report, print_daily_error_info, 0); /* Register extent status tree shrinker */

5 years, 8 months

4
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[PATCH 1/2] x86/entry/64: Do not clear %rbx under Xen

by M. Vefa Bicakci

Commit 3ac6d8c787b8 ("x86/entry/64: Clear registers for exceptions/interrupts, to reduce speculation attack surface") unintendedly broke Xen PV virtual machines by clearing the %rbx register at the end of xen_failsafe_callback before the latter jumps to error_exit. error_exit expects the %rbx register to be a flag indicating whether there should be a return to kernel mode. This commit makes sure that the %rbx register is not cleared by the PUSH_AND_CLEAR_REGS macro, when the macro in question is instantiated by xen_failsafe_callback, to avoid the issue. The impact of this bug includes (and most likely is not limited to) kernel BUGs when wine is run in Xen PV virtual machines. One example is included below. This example depicts the bug when wine is used to run TeamViewer version 13's portable version under a Xen PV virtual machine using an up-to-date version of Qubes OS R3.2. [...........] kernel tried to execute NX-protected page - exploit attempt? (uid: 1000) [ +0.000021] BUG: unable to handle kernel paging request at ffffffff82012480 [ +0.000020] IP: init_task+0x0/0x2ac0 [ +0.000009] PGD 200e067 P4D 200e067 PUD 200f067 PMD 2d5e067 PTE 8010000002012067 [ +0.000019] Oops: 0011 [#1] SMP DEBUG_PAGEALLOC NOPTI [ +0.000015] Modules linked in: fuse bluetooth ecdh_generic rfkill ip6table_filter ip6_tables xt_conntrack ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack libcrc32c intel_rapl x86_pkg_temp_thermal crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel xen_netfront intel_rapl_perf pcspkr binfmt_misc dummy_hcd udc_core xen_gntdev xen_gntalloc u2mfn(O) xen_blkback xenfs xen_evtchn xen_privcmd xen_blkfront [ +0.000091] CPU: 0 PID: 1350 Comm: TeamViewer.exe Tainted: G O 4.14.20-11.d10d0bb86d #15 [ +0.000018] task: ffff8800042fda00 task.stack: ffffc900006f8000 [ +0.000015] RIP: e030:init_task+0x0/0x2ac0 [ +0.000009] RSP: e02b:ffffffff82003df8 EFLAGS: 00010002 [ +0.000012] RAX: 0000000000000040 RBX: 0000000000000004 RCX: 0000000000000000 [ +0.000015] RDX: 0000000000000000 RSI: 0000000000000202 RDI: ffffffff810011aa [ +0.000015] RBP: 000000000033eb88 R08: 0000000000000000 R09: 0000000000000000 [ +0.000015] R10: 0000000000000000 R11: ffff88000d772600 R12: 0000000000000000 [ +0.000015] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ +0.000027] FS: 000000007ffd8000(0063) GS:ffff88000f400000(006b) knlGS:0000000000000000 [ +0.000016] CS: e033 DS: 002b ES: 002b CR0: 0000000080050033 [ +0.000014] CR2: ffffffff82012480 CR3: 0000000004880000 CR4: 0000000000042660 [ +0.000025] Call Trace: [ +0.000007] Code: ff ff ff d0 5a 1e 81 ff ff ff ff 00 00 00 00 00 00 00 00 e0 d7 04 82 ff ff ff ff e8 98 c0 0d 00 88 ff ff 01 80 00 00 00 00 00 00 <00> 00 00 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ +0.000068] RIP: init_task+0x0/0x2ac0 RSP: ffffffff82003df8 [ +0.000011] CR2: ffffffff82012480 [ +0.000010] ---[ end trace 7fb0075d4247b2a2 ]--- The commit that introduces this bug was found with git-bisect in conjunction with some scripts and Qubes OS's cross-VM RPCs for automation, and the correction was prepared after a manual inspection of the changes introduced by the commit in question. To the best of my recollection, this issue is also reproducible in an Ubuntu 18.04 LTS dom0 instance with the version of the Xen hypervisor in Ubuntu's package repositories. Signed-off-by: M. Vefa Bicakci <m.v.b(a)runbox.com> Cc: Dominik Brodowski <linux(a)dominikbrodowski.net> Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky(a)oracle.com> Cc: Juergen Gross <jgross(a)suse.com> Cc: xen-devel(a)lists.xenproject.org Cc: x86(a)kernel.org Cc: stable(a)vger.kernel.org # for v4.14 and up Fixes: 3ac6d8c787b8 ("x86/entry/64: Clear registers for exceptions/interrupts, to reduce speculation attack surface") --- arch/x86/entry/calling.h | 4 +++- arch/x86/entry/entry_64.S | 2 +- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 20d0885b00fb..71795767da94 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -97,7 +97,7 @@ For 32-bit we have the following conventions - kernel is built with #define SIZEOF_PTREGS 21*8 -.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0 +.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0 clear_rbx=1 /* * Push registers and sanitize registers of values that a * speculation attack might otherwise want to exploit. The @@ -127,7 +127,9 @@ For 32-bit we have the following conventions - kernel is built with pushq %r11 /* pt_regs->r11 */ xorl %r11d, %r11d /* nospec r11*/ pushq %rbx /* pt_regs->rbx */ + .if \clear_rbx xorl %ebx, %ebx /* nospec rbx*/ + .endif pushq %rbp /* pt_regs->rbp */ xorl %ebp, %ebp /* nospec rbp*/ pushq %r12 /* pt_regs->r12 */ diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index c7449f377a77..96e8ff34129e 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1129,7 +1129,7 @@ ENTRY(xen_failsafe_callback) addq $0x30, %rsp UNWIND_HINT_IRET_REGS pushq $-1 /* orig_ax = -1 => not a system call */ - PUSH_AND_CLEAR_REGS + PUSH_AND_CLEAR_REGS clear_rbx=0 ENCODE_FRAME_POINTER jmp error_exit END(xen_failsafe_callback) -- 2.17.1

5 years, 8 months

6
23
0 0

[PATCH v3 3/8] drm/fb_helper: Introduce hotplug_suspend/resume()

by Lyude Paul

I'm sure I don't need to tell you that fb_helper's locking is a mess. That being said; fb_helper's locking mess can seriously complicate the runtime suspend/resume operations of drivers because it can invoke atomic commits and connector probing from anywhere that calls drm_fb_helper_hotplug_event(). Since most drivers use drm_fb_helper_output_poll_changed() as their output_poll_changed handler, this can happen in every single context that can fire off a hotplug event. An example: [ 246.669625] INFO: task kworker/4:0:37 blocked for more than 120 seconds. [ 246.673398] Not tainted 4.18.0-rc5Lyude-Test+ #2 [ 246.675271] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 246.676527] kworker/4:0 D 0 37 2 0x80000000 [ 246.677580] Workqueue: events output_poll_execute [drm_kms_helper] [ 246.678704] Call Trace: [ 246.679753] __schedule+0x322/0xaf0 [ 246.680916] schedule+0x33/0x90 [ 246.681924] schedule_preempt_disabled+0x15/0x20 [ 246.683023] __mutex_lock+0x569/0x9a0 [ 246.684035] ? kobject_uevent_env+0x117/0x7b0 [ 246.685132] ? drm_fb_helper_hotplug_event.part.28+0x20/0xb0 [drm_kms_helper] [ 246.686179] mutex_lock_nested+0x1b/0x20 [ 246.687278] ? mutex_lock_nested+0x1b/0x20 [ 246.688307] drm_fb_helper_hotplug_event.part.28+0x20/0xb0 [drm_kms_helper] [ 246.689420] drm_fb_helper_output_poll_changed+0x23/0x30 [drm_kms_helper] [ 246.690462] drm_kms_helper_hotplug_event+0x2a/0x30 [drm_kms_helper] [ 246.691570] output_poll_execute+0x198/0x1c0 [drm_kms_helper] [ 246.692611] process_one_work+0x231/0x620 [ 246.693725] worker_thread+0x214/0x3a0 [ 246.694756] kthread+0x12b/0x150 [ 246.695856] ? wq_pool_ids_show+0x140/0x140 [ 246.696888] ? kthread_create_worker_on_cpu+0x70/0x70 [ 246.697998] ret_from_fork+0x3a/0x50 [ 246.699034] INFO: task kworker/0:1:60 blocked for more than 120 seconds. [ 246.700153] Not tainted 4.18.0-rc5Lyude-Test+ #2 [ 246.701182] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 246.702278] kworker/0:1 D 0 60 2 0x80000000 [ 246.703293] Workqueue: pm pm_runtime_work [ 246.704393] Call Trace: [ 246.705403] __schedule+0x322/0xaf0 [ 246.706439] ? wait_for_completion+0x104/0x190 [ 246.707393] schedule+0x33/0x90 [ 246.708375] schedule_timeout+0x3a5/0x590 [ 246.709289] ? mark_held_locks+0x58/0x80 [ 246.710208] ? _raw_spin_unlock_irq+0x2c/0x40 [ 246.711222] ? wait_for_completion+0x104/0x190 [ 246.712134] ? trace_hardirqs_on_caller+0xf4/0x190 [ 246.713094] ? wait_for_completion+0x104/0x190 [ 246.713964] wait_for_completion+0x12c/0x190 [ 246.714895] ? wake_up_q+0x80/0x80 [ 246.715727] ? get_work_pool+0x90/0x90 [ 246.716649] flush_work+0x1c9/0x280 [ 246.717483] ? flush_workqueue_prep_pwqs+0x1b0/0x1b0 [ 246.718442] __cancel_work_timer+0x146/0x1d0 [ 246.719247] cancel_delayed_work_sync+0x13/0x20 [ 246.720043] drm_kms_helper_poll_disable+0x1f/0x30 [drm_kms_helper] [ 246.721123] nouveau_pmops_runtime_suspend+0x3d/0xb0 [nouveau] [ 246.721897] pci_pm_runtime_suspend+0x6b/0x190 [ 246.722825] ? pci_has_legacy_pm_support+0x70/0x70 [ 246.723737] __rpm_callback+0x7a/0x1d0 [ 246.724721] ? pci_has_legacy_pm_support+0x70/0x70 [ 246.725607] rpm_callback+0x24/0x80 [ 246.726553] ? pci_has_legacy_pm_support+0x70/0x70 [ 246.727376] rpm_suspend+0x142/0x6b0 [ 246.728185] pm_runtime_work+0x97/0xc0 [ 246.728938] process_one_work+0x231/0x620 [ 246.729796] worker_thread+0x44/0x3a0 [ 246.730614] kthread+0x12b/0x150 [ 246.731395] ? wq_pool_ids_show+0x140/0x140 [ 246.732202] ? kthread_create_worker_on_cpu+0x70/0x70 [ 246.732878] ret_from_fork+0x3a/0x50 [ 246.733768] INFO: task kworker/4:2:422 blocked for more than 120 seconds. [ 246.734587] Not tainted 4.18.0-rc5Lyude-Test+ #2 [ 246.735393] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 246.736113] kworker/4:2 D 0 422 2 0x80000080 [ 246.736789] Workqueue: events_long drm_dp_mst_link_probe_work [drm_kms_helper] [ 246.737665] Call Trace: [ 246.738490] __schedule+0x322/0xaf0 [ 246.739250] schedule+0x33/0x90 [ 246.739908] rpm_resume+0x19c/0x850 [ 246.740750] ? finish_wait+0x90/0x90 [ 246.741541] __pm_runtime_resume+0x4e/0x90 [ 246.742370] nv50_disp_atomic_commit+0x31/0x210 [nouveau] [ 246.743124] drm_atomic_commit+0x4a/0x50 [drm] [ 246.743775] restore_fbdev_mode_atomic+0x1c8/0x240 [drm_kms_helper] [ 246.744603] restore_fbdev_mode+0x31/0x140 [drm_kms_helper] [ 246.745373] drm_fb_helper_restore_fbdev_mode_unlocked+0x54/0xb0 [drm_kms_helper] [ 246.746220] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper] [ 246.746884] drm_fb_helper_hotplug_event.part.28+0x96/0xb0 [drm_kms_helper] [ 246.747675] drm_fb_helper_output_poll_changed+0x23/0x30 [drm_kms_helper] [ 246.748544] drm_kms_helper_hotplug_event+0x2a/0x30 [drm_kms_helper] [ 246.749439] nv50_mstm_hotplug+0x15/0x20 [nouveau] [ 246.750111] drm_dp_send_link_address+0x177/0x1c0 [drm_kms_helper] [ 246.750764] drm_dp_check_and_send_link_address+0xa8/0xd0 [drm_kms_helper] [ 246.751602] drm_dp_mst_link_probe_work+0x51/0x90 [drm_kms_helper] [ 246.752314] process_one_work+0x231/0x620 [ 246.752979] worker_thread+0x44/0x3a0 [ 246.753838] kthread+0x12b/0x150 [ 246.754619] ? wq_pool_ids_show+0x140/0x140 [ 246.755386] ? kthread_create_worker_on_cpu+0x70/0x70 [ 246.756162] ret_from_fork+0x3a/0x50 [ 246.756847] Showing all locks held in the system: [ 246.758261] 3 locks held by kworker/4:0/37: [ 246.759016] #0: 00000000f8df4d2d ((wq_completion)"events"){+.+.}, at: process_one_work+0x1b3/0x620 [ 246.759856] #1: 00000000e6065461 ((work_completion)(&(&dev->mode_config.output_poll_work)->work)){+.+.}, at: process_one_work+0x1b3/0x620 [ 246.760670] #2: 00000000cb66735f (&helper->lock){+.+.}, at: drm_fb_helper_hotplug_event.part.28+0x20/0xb0 [drm_kms_helper] [ 246.761516] 2 locks held by kworker/0:1/60: [ 246.762274] #0: 00000000fff6be0f ((wq_completion)"pm"){+.+.}, at: process_one_work+0x1b3/0x620 [ 246.762982] #1: 000000005ab44fb4 ((work_completion)(&dev->power.work)){+.+.}, at: process_one_work+0x1b3/0x620 [ 246.763890] 1 lock held by khungtaskd/64: [ 246.764664] #0: 000000008cb8b5c3 (rcu_read_lock){....}, at: debug_show_all_locks+0x23/0x185 [ 246.765588] 5 locks held by kworker/4:2/422: [ 246.766440] #0: 00000000232f0959 ((wq_completion)"events_long"){+.+.}, at: process_one_work+0x1b3/0x620 [ 246.767390] #1: 00000000bb59b134 ((work_completion)(&mgr->work)){+.+.}, at: process_one_work+0x1b3/0x620 [ 246.768154] #2: 00000000cb66735f (&helper->lock){+.+.}, at: drm_fb_helper_restore_fbdev_mode_unlocked+0x4c/0xb0 [drm_kms_helper] [ 246.768966] #3: 000000004c8f0b6b (crtc_ww_class_acquire){+.+.}, at: restore_fbdev_mode_atomic+0x4b/0x240 [drm_kms_helper] [ 246.769921] #4: 000000004c34a296 (crtc_ww_class_mutex){+.+.}, at: drm_modeset_backoff+0x8a/0x1b0 [drm] [ 246.770839] 1 lock held by dmesg/1038: [ 246.771739] 2 locks held by zsh/1172: [ 246.772650] #0: 00000000836d0438 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 [ 246.773680] #1: 000000001f4f4d48 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0xc1/0x870 [ 246.775522] ============================================= Because of this, there's an unreasonable number of places that drm drivers would need to insert special handling to prevent trying to resume the device from all of these contexts that can deadlock. It's difficult even to try synchronizing with fb_helper in these contexts as well, since any of them could introduce a deadlock by waiting to acquire the top-level fb_helper mutex, while it's being held by another thread that might potentially call down to pm_runtime_get_sync(). Luckily-there's no actual reason we need to allow fb_helper to handle hotplugging at all when runtime suspending a device. If a hotplug happens during a runtime suspend operation, there's no reason the driver can't just re-enable fbcon's hotplug handling and bring it up to speed with hotplugging events it may have missed by calling drm_fb_helper_hotplug_event(). So, let's make this easy and just add helpers to handle disabling and enabling fb_helper connector probing() without having to potentially wait on fb_helper to finish it's work. This will let us fix the runtime suspend/resume deadlocks that we've been experiencing with nouveau, along with being able to fix some of the incorrect runtime PM core interaction that other DRM drivers currently perform to work around these issues. Signed-off-by: Lyude Paul <lyude(a)redhat.com> Cc: stable(a)vger.kernel.org Cc: Lukas Wunner <lukas(a)wunner.de> Cc: Karol Herbst <karolherbst(a)gmail.com> --- drivers/gpu/drm/drm_fb_helper.c | 65 +++++++++++++++++++++++++++++++++ include/drm/drm_fb_helper.h | 20 ++++++++++ 2 files changed, 85 insertions(+) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 2ee1eaa66188..28d59befbc92 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -2733,6 +2733,66 @@ int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel) } EXPORT_SYMBOL(drm_fb_helper_initial_config); +/** + * drm_fb_helper_resume_hotplug - Allow fb_helper to handle probing new + * connectors again, and bring it up to date + * with the current device's connector status + * fb_helper: driver-allocated fbdev helper, can be NULL + * + * Allow fb_helper to react to connector status changes again after having + * been disabled through drm_fb_helper_suspend_hotplug(). This also schedules + * a fb_helper hotplug event to bring fb_helper up to date with the current + * status of the DRM device's connectors. + */ +void +drm_fb_helper_resume_hotplug(struct drm_fb_helper *fb_helper) +{ + fb_helper->hotplug_suspended = false; + drm_fb_helper_hotplug_event(fb_helper); +} +EXPORT_SYMBOL(drm_fb_helper_resume_hotplug); + +/** + * drm_fb_helper_suspend_hotplug - Attempt to temporarily inhibit fb_helper's + * ability to respond to connector changes + * without waiting + * @fb_helper: driver-allocated fbdev helper, can be NULL + * + * Temporarily prevent fb_helper from being able to handle connector changes, + * but only if it isn't busy doing something else. The connector probing + * routines in fb_helper can potentially grab any modesetting lock imaginable, + * which dramatically complicates the runtime suspend process. This helper can + * be used to simplify the process of runtime suspend by allowing the driver + * to disable unpredictable fb_helper operations as early as possible, without + * requiring that we try waiting on fb_helper (as this could lead to very + * difficult to solve deadlocks with runtime suspend code if fb_helper ends up + * needing to acquire a runtime PM reference). + * + * This call should be put at the very start of a driver's runtime suspend + * operation if desired. The driver must be responsible for re-enabling + * fb_helper hotplug handling when normal hotplug detection becomes available + * on the device again. This will usually happen if runtime suspend is + * aborted, or when the device is runtime resumed. + * + * Returns: true if hotplug handling was disabled, false if disabling hotplug + * handling would mean waiting on fb_helper. + */ +bool +drm_fb_helper_suspend_hotplug(struct drm_fb_helper *fb_helper) +{ + int ret; + + ret = mutex_trylock(&fb_helper->lock); + if (!ret) + return false; + + fb_helper->hotplug_suspended = true; + mutex_unlock(&fb_helper->lock); + + return true; +} +EXPORT_SYMBOL(drm_fb_helper_suspend_hotplug); + /** * drm_fb_helper_hotplug_event - respond to a hotplug notification by * probing all the outputs attached to the fb @@ -2774,6 +2834,11 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper) return err; } + if (fb_helper->hotplug_suspended) { + mutex_unlock(&fb_helper->lock); + return err; + } + DRM_DEBUG_KMS("\n"); drm_setup_crtcs(fb_helper, fb_helper->fb->width, fb_helper->fb->height); diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h index b069433e7fc1..30881131075c 100644 --- a/include/drm/drm_fb_helper.h +++ b/include/drm/drm_fb_helper.h @@ -232,6 +232,14 @@ struct drm_fb_helper { * See also: @deferred_setup */ int preferred_bpp; + + /** + * @hotplug_suspended: + * + * Whether or not we can currently handle hotplug events, or if we + * need to wait for the DRM device to uninhibit us. + */ + bool hotplug_suspended; }; /** @@ -330,6 +338,10 @@ void drm_fb_helper_fbdev_teardown(struct drm_device *dev); void drm_fb_helper_lastclose(struct drm_device *dev); void drm_fb_helper_output_poll_changed(struct drm_device *dev); + +void drm_fb_helper_resume_hotplug(struct drm_fb_helper *fb_helper); +bool drm_fb_helper_suspend_hotplug(struct drm_fb_helper *fb_helper); + #else static inline void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper, @@ -564,6 +576,14 @@ static inline void drm_fb_helper_output_poll_changed(struct drm_device *dev) { } +static inline void +drm_fb_helper_resume_hotplug(struct drm_fb_helper *fb_helper) +{ +} +static inline bool +drm_fb_helper_suspend_hotplug(struct drm_fb_helper *fb_helper) +{ +} #endif static inline int -- 2.17.1

5 years, 9 months

5
7
0 0

[PATCH] stop_machine: Disable preemption after queueing stopper threads

by Isaac J. Manjarres

This commit: 9fb8d5dc4b64 ("stop_machine, Disable preemption when waking two stopper threads") does not fully address the race condition that can occur as follows: On one CPU, call it CPU 3, thread 1 invokes cpu_stop_queue_two_works(2, 3,...), and the execution is such that thread 1 queues the works for migration/2 and migration/3, and is preempted after releasing the locks for migration/2 and migration/3, but before waking the threads. Then, On CPU 2, a kworker, call it thread 2, is running, and it invokes cpu_stop_queue_two_works(1, 2,...), such that thread 2 queues the works for migration/1 and migration/2. Meanwhile, on CPU 3, thread 1 resumes execution, and wakes migration/2 and migration/3. This means that when CPU 2 releases the locks for migration/1 and migration/2, but before it wakes those threads, it can be preempted by migration/2. If thread 2 is preempted by migration/2, then migration/2 will execute the first work item successfully, since migration/3 was woken up by CPU 3, but when it goes to execute the second work item, it disables preemption, calls multi_cpu_stop(), and thus, CPU 2 will wait forever for migration/1, which should have been woken up by thread 2. However migration/1 cannot be woken up by thread 2, since it is a kworker, so it is affine to CPU 2, but CPU 2 is running migration/2 with preemption disabled, so thread 2 will never run. Disable preemption after queueing works for stopper threads to ensure that the operation of queueing the works and waking the stopper threads is atomic. Fixes: 9fb8d5dc4b64 ("stop_machine, Disable preemption when waking two stopper threads") Co-Developed-by: Prasad Sodagudi <psodagud(a)codeaurora.org> Co-Developed-by: Pavankumar Kondeti <pkondeti(a)codeaurora.org> Signed-off-by: Isaac J. Manjarres <isaacm(a)codeaurora.org> Signed-off-by: Prasad Sodagudi <psodagud(a)codeaurora.org> Signed-off-by: Pavankumar Kondeti <pkondeti(a)codeaurora.org> Cc: stable(a)vger.kernel.org --- kernel/stop_machine.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 1ff523d..e190d1e 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -260,6 +260,15 @@ static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1, err = 0; __cpu_stop_queue_work(stopper1, work1, &wakeq); __cpu_stop_queue_work(stopper2, work2, &wakeq); + /* + * The waking up of stopper threads has to happen + * in the same scheduling context as the queueing. + * Otherwise, there is a possibility of one of the + * above stoppers being woken up by another CPU, + * and preempting us. This will cause us to n ot + * wake up the other stopper forever. + */ + preempt_disable(); unlock: raw_spin_unlock(&stopper2->lock); raw_spin_unlock_irq(&stopper1->lock); @@ -271,7 +280,6 @@ static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1, } if (!err) { - preempt_disable(); wake_up_q(&wakeq); preempt_enable(); } -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project

5 years, 9 months

7
11
0 0

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Linux-stable-mirror July 2018