On 2/14/2019 9:40 PM, Chao Yu wrote:
On 2019-2-14 15:46, Sahitya Tummala wrote:
On Wed, Feb 13, 2019 at 11:25:31AM +0800, Chao Yu wrote:
On 2019/2/4 16:06, Sahitya Tummala wrote:
Fix below warning coming because of using mutex lock in atomic context.
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:98
in_atomic(): 1, irqs_disabled(): 0, pid: 585, name: sh
Preemption disabled at: __radix_tree_preload+0x28/0x130
Call trace:
dump_backtrace+0x0/0x2b4
show_stack+0x20/0x28
dump_stack+0xa8/0xe0
___might_sleep+0x144/0x194
__might_sleep+0x58/0x8c
mutex_lock+0x2c/0x48
f2fs_trace_pid+0x88/0x14c
f2fs_set_node_page_dirty+0xd0/0x184
Do not use f2fs_radix_tree_insert() to avoid doing cond_resched() with
spin_lock() acquired.
Signed-off-by: Sahitya Tummala <stumm...@codeaurora.org>
---
fs/f2fs/trace.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/fs/f2fs/trace.c b/fs/f2fs/trace.c
index ce2a5eb..d0ab533 100644
--- a/fs/f2fs/trace.c
+++ b/fs/f2fs/trace.c
@@ -14,7 +14,7 @@
#include "trace.h"
static RADIX_TREE(pids, GFP_ATOMIC);
-static struct mutex pids_lock;
+static spinlock_t pids_lock;
static struct last_io_info last_io;
static inline void __print_last_io(void)
@@ -58,23 +58,29 @@ void f2fs_trace_pid(struct page *page)
set_page_private(page, (unsigned long)pid);
+retry:
if (radix_tree_preload(GFP_NOFS))
return;
- mutex_lock(&pids_lock);
+ spin_lock(&pids_lock);
p = radix_tree_lookup(&pids, pid);
if (p == current)
goto out;
if (p)
radix_tree_delete(&pids, pid);
- f2fs_radix_tree_insert(&pids, pid, current);
Do you know why do we have a retry logic here? When anyways we have
called for radix_tree_delete with pid key?
Which should ensure the slot is empty, no?
Then why in the original code (f2fs_radix_tree_insert), we were
retrying. For what condition a retry was needed?
Regards
Ritesh
+ if (radix_tree_insert(&pids, pid, current)) {
+ spin_unlock(&pids_lock);
+ radix_tree_preload_end();
+ cond_resched();
+ goto retry;
+ }
trace_printk("%3x:%3x %4x %-16s\n",
MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
pid, current->comm);
Hi Sahitya,
Can trace_printk sleep? For safety, how about moving it out of spinlock?
Hi Chao,
Yes, trace_printk() is safe to use in atomic context (unlike printk).
Hi Sahitya,
Thanks for your confirmation. :)
Reviewed-by: Chao Yu <yuch...@huawei.com>
Thanks,
Thanks,
Sahitya.
Thanks,
out:
- mutex_unlock(&pids_lock);
+ spin_unlock(&pids_lock);
radix_tree_preload_end();
}
@@ -119,7 +125,7 @@ void f2fs_trace_ios(struct f2fs_io_info *fio, int flush)
void f2fs_build_trace_ios(void)
{
- mutex_init(&pids_lock);
+ spin_lock_init(&pids_lock);
}
#define PIDVEC_SIZE 128
@@ -147,7 +153,7 @@ void f2fs_destroy_trace_ios(void)
pid_t next_pid = 0;
unsigned int found;
- mutex_lock(&pids_lock);
+ spin_lock(&pids_lock);
while ((found = gang_lookup_pids(pid, next_pid, PIDVEC_SIZE))) {
unsigned idx;
@@ -155,5 +161,5 @@ void f2fs_destroy_trace_ios(void)
for (idx = 0; idx < found; idx++)
radix_tree_delete(&pids, pid[idx]);
}
- mutex_unlock(&pids_lock);
+ spin_unlock(&pids_lock);
}
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