6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michael Ellerman mpe@ellerman.id.au
[ Upstream commit cadae3a45d23aa4f6485938a67cbc47aaaa25e38 ]
The dtl_access_lock needs to be a rw_sempahore, a sleeping lock, because the code calls kmalloc() while holding it, which can sleep:
# echo 1 > /proc/powerpc/vcpudispatch_stats BUG: sleeping function called from invalid context at include/linux/sched/mm.h:337 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 199, name: sh preempt_count: 1, expected: 0 3 locks held by sh/199: #0: c00000000a0743f8 (sb_writers#3){.+.+}-{0:0}, at: vfs_write+0x324/0x438 #1: c0000000028c7058 (dtl_enable_mutex){+.+.}-{3:3}, at: vcpudispatch_stats_write+0xd4/0x5f4 #2: c0000000028c70b8 (dtl_access_lock){+.+.}-{2:2}, at: vcpudispatch_stats_write+0x220/0x5f4 CPU: 0 PID: 199 Comm: sh Not tainted 6.10.0-rc4 #152 Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries Call Trace: dump_stack_lvl+0x130/0x148 (unreliable) __might_resched+0x174/0x410 kmem_cache_alloc_noprof+0x340/0x3d0 alloc_dtl_buffers+0x124/0x1ac vcpudispatch_stats_write+0x2a8/0x5f4 proc_reg_write+0xf4/0x150 vfs_write+0xfc/0x438 ksys_write+0x88/0x148 system_call_exception+0x1c4/0x5a0 system_call_common+0xf4/0x258
Fixes: 06220d78f24a ("powerpc/pseries: Introduce rwlock to gatekeep DTLB usage") Tested-by: Kajol Jain kjain@linux.ibm.com Reviewed-by: Nysal Jan K.A nysal@linux.ibm.com Reviewed-by: Kajol Jain kjain@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://patch.msgid.link/20240819122401.513203-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/include/asm/dtl.h | 4 ++-- arch/powerpc/platforms/pseries/dtl.c | 8 ++++---- arch/powerpc/platforms/pseries/lpar.c | 8 ++++---- 3 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/include/asm/dtl.h b/arch/powerpc/include/asm/dtl.h index d6f43d149f8dc..a5c21bc623cb0 100644 --- a/arch/powerpc/include/asm/dtl.h +++ b/arch/powerpc/include/asm/dtl.h @@ -1,8 +1,8 @@ #ifndef _ASM_POWERPC_DTL_H #define _ASM_POWERPC_DTL_H
+#include <linux/rwsem.h> #include <asm/lppaca.h> -#include <linux/spinlock_types.h>
/* * Layout of entries in the hypervisor's dispatch trace log buffer. @@ -35,7 +35,7 @@ struct dtl_entry { #define DTL_LOG_ALL (DTL_LOG_CEDE | DTL_LOG_PREEMPT | DTL_LOG_FAULT)
extern struct kmem_cache *dtl_cache; -extern rwlock_t dtl_access_lock; +extern struct rw_semaphore dtl_access_lock;
extern void register_dtl_buffer(int cpu); extern void alloc_dtl_buffers(unsigned long *time_limit); diff --git a/arch/powerpc/platforms/pseries/dtl.c b/arch/powerpc/platforms/pseries/dtl.c index 8cb9d36ea4915..f293588b8c7b5 100644 --- a/arch/powerpc/platforms/pseries/dtl.c +++ b/arch/powerpc/platforms/pseries/dtl.c @@ -191,7 +191,7 @@ static int dtl_enable(struct dtl *dtl) return -EBUSY;
/* ensure there are no other conflicting dtl users */ - if (!read_trylock(&dtl_access_lock)) + if (!down_read_trylock(&dtl_access_lock)) return -EBUSY;
n_entries = dtl_buf_entries; @@ -199,7 +199,7 @@ static int dtl_enable(struct dtl *dtl) if (!buf) { printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n", __func__, dtl->cpu); - read_unlock(&dtl_access_lock); + up_read(&dtl_access_lock); return -ENOMEM; }
@@ -217,7 +217,7 @@ static int dtl_enable(struct dtl *dtl) spin_unlock(&dtl->lock);
if (rc) { - read_unlock(&dtl_access_lock); + up_read(&dtl_access_lock); kmem_cache_free(dtl_cache, buf); }
@@ -232,7 +232,7 @@ static void dtl_disable(struct dtl *dtl) dtl->buf = NULL; dtl->buf_entries = 0; spin_unlock(&dtl->lock); - read_unlock(&dtl_access_lock); + up_read(&dtl_access_lock); }
/* file interface */ diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index c1d8bee8f7018..bb09990eec309 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -169,7 +169,7 @@ struct vcpu_dispatch_data { */ #define NR_CPUS_H NR_CPUS
-DEFINE_RWLOCK(dtl_access_lock); +DECLARE_RWSEM(dtl_access_lock); static DEFINE_PER_CPU(struct vcpu_dispatch_data, vcpu_disp_data); static DEFINE_PER_CPU(u64, dtl_entry_ridx); static DEFINE_PER_CPU(struct dtl_worker, dtl_workers); @@ -463,7 +463,7 @@ static int dtl_worker_enable(unsigned long *time_limit) { int rc = 0, state;
- if (!write_trylock(&dtl_access_lock)) { + if (!down_write_trylock(&dtl_access_lock)) { rc = -EBUSY; goto out; } @@ -479,7 +479,7 @@ static int dtl_worker_enable(unsigned long *time_limit) pr_err("vcpudispatch_stats: unable to setup workqueue for DTL processing\n"); free_dtl_buffers(time_limit); reset_global_dtl_mask(); - write_unlock(&dtl_access_lock); + up_write(&dtl_access_lock); rc = -EINVAL; goto out; } @@ -494,7 +494,7 @@ static void dtl_worker_disable(unsigned long *time_limit) cpuhp_remove_state(dtl_worker_state); free_dtl_buffers(time_limit); reset_global_dtl_mask(); - write_unlock(&dtl_access_lock); + up_write(&dtl_access_lock); }
static ssize_t vcpudispatch_stats_write(struct file *file, const char __user *p,