Let us say we have X/Y path in the file system. We have attr_lock and
content_lock on each object. The locks we are interested here are
attr_lock on X (hear after referred to as AX) and content_lock on X
(hear after CX). Similarly we have AY and CY for object named Y.
1. Thread 50 (lookup called for X ) takes AX and waits for CX (attr_lock
followed by content_lock is the expected order)
2. Thread 251 (readdirplus on X) takes CX, AY and then waits for CY for
processing object Y
3. Thread 132 (readdirplus on Y) takes CY, and then waits for AX (this
is due to lookup of parent)
Classic philosopher's problem: 1 waits for 2, 2 waits for 3 and then 3
waits for 1. The lock ordering for attr_lock and content_lock for an
object is attr_lock followed by content_lock. We can assume that parent
locks should be acquired before the child locks, but DOTDOT appears as a
child in readdirplus/readdir. If we can handle parent differently, we
might be OK. Any help would be appreciated.
Regards, Malahal.
(gdb) thread 50
[Switching to thread 50 (Thread 0x3fff6cffe850 (LWP 37851))]
#0 0x00003fff8a50089c in .__pthread_rwlock_wrlock () from
/lib64/libpthread.so.0
(gdb) bt
#0 0x00003fff8a50089c in .__pthread_rwlock_wrlock () from
/lib64/libpthread.so.0
#1 0x00000000101adaa4 in mdcache_refresh_attrs (entry=0x3ffccc0541f0,
need_acl=false, invalidate=true)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:1187
#2 0x00000000101ae1b0 in mdcache_getattrs (obj_hdl=0x3ffccc054228,
attrs_out=0x3fff6cffcfb8)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:1228
#3 0x00000000100b9fdc in nfs_SetPostOpAttr (obj=0x3ffccc054228,
Fattr=0x3ffe64050dc8, attrs=0x0)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/Protocols/NFS/nfs_proto_tools.c:91
#4 0x00000000100c6ba8 in nfs3_lookup (arg=0x3ffa9ff04780,
req=0x3ffa9ff03f78, res=0x3ffe64050d50)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/Protocols/NFS/nfs3_lookup.c:131
#5 0x0000000010065220 in nfs_rpc_execute (reqdata=0x3ffa9ff03f50)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/MainNFSD/nfs_worker_thread.c:1290
#6 0x0000000010065c9c in worker_run (ctx=0x10013c1d3f0)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/MainNFSD/nfs_worker_thread.c:1562
#7 0x00000000101670f4 in fridgethr_start_routine (arg=0x10013c1d3f0)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/support/fridgethr.c:550
#8 0x00003fff8a4fc2bc in .start_thread () from /lib64/libpthread.so.0
#9 0x00003fff8a31b304 in .__clone () from /lib64/libc.so.6
(gdb) frame 1
#1 0x00000000101adaa4 in mdcache_refresh_attrs (entry=0x3ffccc0541f0,
need_acl=false, invalidate=true)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:1187
1187 PTHREAD_RWLOCK_wrlock(&entry->content_lock);
(gdb) p entry
$1 = (mdcache_entry_t *) 0x3ffccc0541f0
(gdb) p entry->content_lock
$2 = {__data = {__lock = 0, __nr_readers = 1, __readers_wakeup = 2408,
__writer_wakeup = 4494, __nr_readers_queued = 0,
__nr_writers_queued = 6, __writer = 0, __shared = 0, __pad1 = 0, __pad2
= 0, __flags = 0},
__size =
"\000\000\000\000\000\000\000\001\000\000\th\000\000\021\216\000\000\000\000\000\000\000\006",
'\000' <repeats 31 times>, __align = 1}
(gdb) thread 251
[Switching to thread 251 (Thread 0x3fff2e7fe850 (LWP 37976))]
#0 0x00003fff8a50089c in .__pthread_rwlock_wrlock () from
/lib64/libpthread.so.0
(gdb) bt
#0 0x00003fff8a50089c in .__pthread_rwlock_wrlock () from
/lib64/libpthread.so.0
#1 0x00000000101adaa4 in mdcache_refresh_attrs (entry=0x3ffc30041bd0,
need_acl=false, invalidate=true)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:1187
#2 0x00000000101ae1b0 in mdcache_getattrs (obj_hdl=0x3ffc30041c08,
attrs_out=0x3fff2e7fcb58)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:1228
#3 0x00000000101c0f50 in mdcache_readdir_chunked
(directory=0x3ffccc0541f0, whence=1298220731,
dir_state=0x3fff2e7fcee8, cb=@0x1024b040: 0x1003f524 <populate_dirent>,
attrmask=122830, eod_met=0x3fff2e7fd01c)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_helpers.c:3047
#4 0x00000000101ab998 in mdcache_readdir (dir_hdl=0x3ffccc054228,
whence=0x3fff2e7fcfa0, dir_state=0x3fff2e7fcee8,
cb=@0x1024b040: 0x1003f524 <populate_dirent>, attrmask=122830,
eod_met=0x3fff2e7fd01c)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:637
#5 0x0000000010040090 in fsal_readdir (directory=0x3ffccc054228,
cookie=1298220731, nbfound=0x3fff2e7fd018,
eod_met=0x3fff2e7fd01c, attrmask=122830, cb=@0x10250bb0: 0x100cabf4
<nfs3_readdirplus_callback>,
opaque=0x3fff2e7fd038) at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/fsal_helper.c:1504
#6 0x00000000100ca90c in nfs3_readdirplus (arg=0x3ffa14114820,
req=0x3ffa14114018, res=0x3ffc6c0540c0)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/Protocols/NFS/nfs3_readdirplus.c:309
#7 0x0000000010065220 in nfs_rpc_execute (reqdata=0x3ffa14113ff0)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/MainNFSD/nfs_worker_thread.c:1290
#8 0x0000000010065c9c in worker_run (ctx=0x10013c41c30)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/MainNFSD/nfs_worker_thread.c:1562
#9 0x00000000101670f4 in fridgethr_start_routine (arg=0x10013c41c30)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/support/fridgethr.c:550
#10 0x00003fff8a4fc2bc in .start_thread () from /lib64/libpthread.so.0
#11 0x00003fff8a31b304 in .__clone () from /lib64/libc.so.6
(gdb) frame 1
#1 0x00000000101adaa4 in mdcache_refresh_attrs (entry=0x3ffc30041bd0,
need_acl=false, invalidate=true)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:1187
1187 PTHREAD_RWLOCK_wrlock(&entry->content_lock);
(gdb) p entry
$3 = (mdcache_entry_t *) 0x3ffc30041bd0
(gdb) p entry->content_lock
$4 = {__data = {__lock = 0, __nr_readers = 1, __readers_wakeup = 3,
__writer_wakeup = 2, __nr_readers_queued = 0,
__nr_writers_queued = 1, __writer = 0, __shared = 0, __pad1 = 0, __pad2
= 0, __flags = 0},
__size =
"\000\000\000\000\000\000\000\001\000\000\000\003\000\000\000\002\000\000\000\000\000\000\000\001",
'\000' <repeats 31 times>, __align = 1}
(gdb) thread 132
[Switching to thread 132 (Thread 0x3fff1b7fe850 (LWP 38014))]
#0 0x00003fff8a500428 in .__pthread_rwlock_rdlock () from
/lib64/libpthread.so.0
(gdb) bt
#0 0x00003fff8a500428 in .__pthread_rwlock_rdlock () from
/lib64/libpthread.so.0
#1 0x00000000101adda0 in mdcache_getattrs (obj_hdl=0x3ffccc054228,
attrs_out=0x3fff1b7fd140)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:1212
#2 0x00000000101b7280 in get_optional_attrs (obj_hdl=0x3ffccc054228,
attrs_out=0x3fff1b7fd140)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_helpers.c:135
#3 0x00000000101ba3d8 in mdcache_locate_host (fh_desc=0x3ffc30042148,
export=0x10010c6b710, entry=0x3fff1b7fceb0,
attrs_out=0x3fff1b7fd140)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_helpers.c:972
#4 0x00000000101bb1f8 in mdc_lookup (mdc_parent=0x3ffc30041bd0,
name=0x101dd8e0 "..", uncached=true,
new_entry=0x3fff1b7fceb0, attrs_out=0x3fff1b7fd140)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_helpers.c:1213
#5 0x00000000101a9518 in mdcache_lookup (parent=0x3ffc30041c08,
name=0x101dd8e0 "..", handle=0x3fff1b7fd220,
attrs_out=0x3fff1b7fd140)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:175
#6 0x000000001003dba4 in fsal_lookupp (obj=0x3ffc30041c08,
parent=0x3fff1b7fd220, attrs_out=0x3fff1b7fd140)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/fsal_helper.c:756
#7 0x00000000100ca7fc in nfs3_readdirplus (arg=0x3ffef3f05a00,
req=0x3ffef3f051f8, res=0x3ffbd4058e40)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/Protocols/NFS/nfs3_readdirplus.c:281
#8 0x0000000010065220 in nfs_rpc_execute (reqdata=0x3ffef3f051d0)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/MainNFSD/nfs_worker_thread.c:1290
#9 0x0000000010065c9c in worker_run (ctx=0x10013c4d0b0)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/MainNFSD/nfs_worker_thread.c:1562
#10 0x00000000101670f4 in fridgethr_start_routine (arg=0x10013c4d0b0)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/support/fridgethr.c:550
#11 0x00003fff8a4fc2bc in .start_thread () from /lib64/libpthread.so.0
#12 0x00003fff8a31b304 in .__clone () from /lib64/libc.so.6
(gdb) frame 1
#1 0x00000000101adda0 in mdcache_getattrs (obj_hdl=0x3ffccc054228,
attrs_out=0x3fff1b7fd140)
at
/usr/src/debug/nfs-ganesha-2.5.3-ibm008.20M6-0.1.1-Source/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c:1212
1212 PTHREAD_RWLOCK_rdlock(&entry->attr_lock);
(gdb) p entry
$5 = (mdcache_entry_t *) 0x3ffccc0541f0
(gdb) p entry->attr_lock
$6 = {__data = {__lock = 0, __nr_readers = 0, __readers_wakeup = 1306,
__writer_wakeup = 276,
__nr_readers_queued = 215, __nr_writers_queued = 0, __writer = 37851,
__shared = 0, __pad1 = 0, __pad2 = 0,
__flags = 0},
__size =
"\000\000\000\000\000\000\000\000\000\000\005\032\000\000\001\024\000\000\000\327\000\000\000\000\000\000\223\333",
'\000' <repeats 27 times>, __align = 0}
(gdb)
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