This is a note to let you know that I've just added the patch titled
powerpc/pseries: Fix dtl_access_lock to be a rw_semaphore
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-pseries-fix-dtl_access_lock-to-be-a-rw_semap.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 18b0e676360220cb521c87295027776a6842a277
Author: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Date: Mon Aug 19 22:24:01 2024 +1000
powerpc/pseries: Fix dtl_access_lock to be a rw_semaphore
[ 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@xxxxxxxxxxxxx>
Reviewed-by: Nysal Jan K.A <nysal@xxxxxxxxxxxxx>
Reviewed-by: Kajol Jain <kjain@xxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://patch.msgid.link/20240819122401.513203-1-mpe@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/powerpc/include/asm/dtl.h b/arch/powerpc/include/asm/dtl.h
index 4bcb9f9ac7649..859af5de3c2f9 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 3f1cdccebc9c1..ecc04ef8c53e3 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 29d235b02f062..98f8e0a39eb2f 100644
--- a/arch/powerpc/platforms/pseries/lpar.c
+++ b/arch/powerpc/platforms/pseries/lpar.c
@@ -167,7 +167,7 @@ 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);
@@ -461,7 +461,7 @@ 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;
}
@@ -477,7 +477,7 @@ 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;
}
@@ -492,7 +492,7 @@ 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,
