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powerpc/pseries: Fix dtl_access_lock to be a rw_semaphore

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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: 06220d78f2 ("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
This commit is contained in:
Michael Ellerman 2024-08-19 22:24:01 +10:00
parent b23b9edf64
commit cadae3a45d
3 changed files with 10 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

4
arch/powerpc/include/asm/dtl.h
View file

@ -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);

8
arch/powerpc/platforms/pseries/dtl.c
View file

@ -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 */

8
arch/powerpc/platforms/pseries/lpar.c
View file

@ -170,7 +170,7 @@ 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);
@ -464,7 +464,7 @@ 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;
}
@ -480,7 +480,7 @@ 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;
}
@ -495,7 +495,7 @@ 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,