Re: [PATCH] hash: fix memcmp function pointer in multi-process environment

[Dhananjaya Eadala <edreddy@gmail.com>]

Hi

I looked at your info from gdb and source code.
 From source code, rte_hash_lookup_with_hash / 
__rte_hash_lookup_with_hash() function doesn't invoke rte_hash_reset() 
function.
It may be possible that rte_hash_cmp_eq function pointer from one 
process is matching to address of rte_hash_reset () in other process.

For quick test, you can do two things.

1. just apply the patch I provided and recompile the dpdk with a -D flag 
"RTE_LIB_MP_NO_FUNC_PTR" defined and re-run your test

2. If it still crashes, disable the optimization in Makefiles and see, 
using gdb, how you are entering rte_hash_reset() from 
__rte_hash_lookup_with_hash(). this will tell you if it was a problem 
with function pointers in multi-process environment


Thanks
Dhana

On 03/14/2016 12:38 AM, 张伟 wrote:
> BTW, the following is my backtrace when the system crashes.
>
> Program received signal SIGSEGV, Segmentation fault.
>
> 0x00000000004883ab in rte_hash_reset (h=0x0)
>
>     at 
> /home/zhangwei1984/timopenNetVM/dpdk-2.2.0/lib/librte_hash/rte_cuckoo_hash.c:444
>
> 444while (rte_ring_dequeue(h->free_slots, &ptr) == 0)
>
> (gdb) bt
>
> #0  0x00000000004883ab in rte_hash_reset (h=0x0)
>
>     at 
> /home/zhangwei1984/timopenNetVM/dpdk-2.2.0/lib/librte_hash/rte_cuckoo_hash.c:444
>
> #1  0x000000000048fdfb in rte_hash_lookup_with_hash (h=0x7fff32cce740, 
> key=0x7fffffffe220, sig=403183624)
>
>     at 
> /home/zhangwei1984/timopenNetVM/dpdk-2.2.0/lib/librte_hash/rte_cuckoo_hash.c:771
>
> #2  0x000000000042b551 in onvm_ft_lookup_with_hash 
> (table=0x7fff32cbe4c0, pkt=0x7fff390ea9c0,
>
>     data=0x7fffffffe298) at 
> /home/zhangwei1984/openNetVM-master/openNetVM/onvm/shared/onvm_flow_table.c:104
>
> #3  0x000000000042b8c3 in onvm_flow_dir_get_with_hash 
> (table=0x7fff32cbe4c0, pkt=0x7fff390ea9c0,
>
> flow_entry=0x7fffffffe298)
>
>     at 
> /home/zhangwei1984/openNetVM-master/openNetVM/onvm/shared/onvm_flow_dir.c:14
>
> #4  0x00000000004251d7 in packet_handler (pkt=0x7fff390ea9c0, 
> meta=0x7fff390eaa00)
>
>     at 
> /home/zhangwei1984/openNetVM-master/openNetVM/examples/flow_table/flow_table.c:212
>
> #5  0x0000000000429502 in onvm_nf_run ()
>
> #6  0x00000000004253f1 in main (argc=1, argv=0x7fffffffe648)
>
>     at 
> /home/zhangwei1984/openNetVM-master/openNetVM/examples/flow_table/flow_table.c:272
>
> (gdb)
>
>
>
>
> I met a problem which I used the DPDK hash table for multi processes. 
> One started as primary process and the other as secondary process.
> I based on the client and server multiprocess example. My aim is that 
> server creates a hash table, then share it to the client. The client 
> will read and write the hash table, and the server will read the hash 
> table. I use rte_calloc allocate the space for hash table, use memzone 
> tells the client the hash table address.
> But once I add an entry into the hash table, calling "lookup" function 
> will have the segment fault. But for the lookup function, I have 
> exactly the same parameters for lookup when the first time calls the 
> lookup.
> If I create the hash table inside the client, everything works correctly.
> I put pieces of codes for server and client codes related to the hash 
> table. I have spent almost 3 days on this bug. But there is no any 
> clue which can help to solve this bug. If any of you can give some 
> suggestions, I will be appreciated. I post the question into the mail 
> list, but have not yet got any reply.
>
> This problem is that in dpdk multi process - client and server 
> example, dpdk-2.2.0/examples/multi_process/client_server_mp
> My aim is that server create a hash table, then share it to client. 
> Client will write the hash  table, server will read the hash table.  I 
> am using dpdk hash table.  What I did is that server create a hash 
> table (table and array entries), return the table address.  I use 
> memzone pass the table address to client.  In client, the second 
> lookup gets segment fault. The system gets crashed.  I will put some 
> related code here.
> create hash table function:
>
> struct onvm_ft*
>
> onvm_ft_create(int cnt, int entry_size) {
>
>         struct rte_hash* hash;
>
>         struct onvm_ft* ft;
>
>         struct rte_hash_parameters ipv4_hash_params = {
>
>             .name = NULL,
>
>             .entries = cnt,
>
>             .key_len = sizeof(struct onvm_ft_ipv4_5tuple),
>
>             .hash_func = NULL,
>
>             .hash_func_init_val = 0,
>
>         };
>
>
>         char s[64];
>
>         /* create ipv4 hash table. use core number and cycle counter 
> to get a unique name. */
>
> ipv4_hash_params.name <http://ipv4_hash_params.name/> = s;
>
>         ipv4_hash_params.socket_id = rte_socket_id();
>
>         snprintf(s, sizeof(s), "onvm_ft_%d-%"PRIu64, rte_lcore_id(), 
> rte_get_tsc_cycles());
>
>         hash = rte_hash_create(&ipv4_hash_params);
>
>         if (hash == NULL) {
>
>                 return NULL;
>
>         }
>
>         ft = 
> (struct onvm_ft*)rte_calloc("table", 1, sizeof(struct onvm_ft), 0);
>
>         if (ft == NULL) {
>
>                 rte_hash_free(hash);
>
>                 return NULL;
>
>         }
>
>         ft->hash = hash;
>
>         ft->cnt = cnt;
>
>         ft->entry_size = entry_size;
>
>         /* Create data array for storing values */
>
>         ft->data = rte_calloc("entry", cnt, entry_size, 0);
>
>         if (ft->data == NULL) {
>
>                 rte_hash_free(hash);
>
>                 rte_free(ft);
>
>                 return NULL;
>
>         }
>
>         return ft;
>
> }
>
>
> related structure:
>
> struct onvm_ft {
>
>         struct rte_hash* hash;
>
>         char* data;
>
>         int cnt;
>
>         int entry_size;
>
> };
>
>
> in server side, I will call the create function, use memzone share it 
> to client. The following is what I do:
>
> related variables:
>
> struct onvm_ft *sdn_ft;
>
> struct onvm_ft **sdn_ft_p;
>
> const struct rte_memzone *mz_ftp;
>
>
>         sdn_ft = onvm_ft_create(1024, sizeof(struct onvm_flow_entry));
>
>         if(sdn_ft == NULL) {
>
>                 rte_exit(EXIT_FAILURE, "Unable to create flow table\n");
>
>         }
>
>         mz_ftp = 
> rte_memzone_reserve(MZ_FTP_INFO, sizeof(struct onvm_ft *),
>
>                                   rte_socket_id(), NO_FLAGS);
>
>         if (mz_ftp == NULL) {
>
>                 rte_exit(EXIT_FAILURE, "Canot reserve memory zone for 
> flow table pointer\n");
>
>         }
>
>         memset(mz_ftp->addr, 0, sizeof(struct onvm_ft *));
>
>         sdn_ft_p = mz_ftp->addr;
>
>         *sdn_ft_p = sdn_ft;
>
>
> In client side:
>
> struct onvm_ft *sdn_ft;
>
> static void
>
> map_flow_table(void) {
>
>         const struct rte_memzone *mz_ftp;
>
>         struct onvm_ft **ftp;
>
>
>         mz_ftp = rte_memzone_lookup(MZ_FTP_INFO);
>
>         if (mz_ftp == NULL)
>
>                 rte_exit(EXIT_FAILURE, "Cannot get flow table pointer\n");
>
>         ftp = mz_ftp->addr;
>
>         sdn_ft = *ftp;
>
> }
>
>
> The following is my debug message: I set a breakpoint in lookup table 
> line. To narrow down the problem, I just send one flow. So the second 
> time and the first time, the packets are the same.
>
> For the first time, it works. I print out the parameters: inside the 
> onvm_ft_lookup function, if there is a related entry, it will return 
> the address by flow_entry.
>
> Breakpoint 1, datapath_handle_read (dp=0x7ffff00008c0) at 
> /home/zhangwei1984/openNetVM-master/openNetVM/examples/flow_table/sdn.c:191
>
> 191                                 ret = onvm_ft_lookup(sdn_ft, fk, 
> (char**)&flow_entry);
>
> (gdb) print *sdn_ft
>
> $1 = {hash = 0x7fff32cce740, data = 0x7fff32cb0480 "", cnt = 1024, 
> entry_size = 56}
>
> (gdb) print *fk
>
> $2 = {src_addr = 419496202, dst_addr = 453050634, src_port = 53764, 
> dst_port = 11798, proto = 17 '\021'}
>
> (gdb) s
>
> onvm_ft_lookup (table=0x7fff32cbe4c0, key=0x7fff32b99d00, 
> data=0x7ffff68d2b00) at 
> /home/zhangwei1984/openNetVM-master/openNetVM/onvm/shared/onvm_flow_table.c:151
>
> 151 softrss = onvm_softrss(key);
>
> (gdb) n
>
> 152         printf("software rss %d\n", softrss);
>
> (gdb)
>
> software rss 403183624
>
> 154         tbl_index = rte_hash_lookup_with_hash(table->hash, (const 
> void *)key, softrss);
>
> (gdb) print table->hash
>
> $3 = (struct rte_hash *) 0x7fff32cce740
>
> (gdb) print *key
>
> $4 = {src_addr = 419496202, dst_addr = 453050634, src_port = 53764, 
> dst_port = 11798, proto = 17 '\021'}
>
> (gdb) print softrss
>
> $5 = 403183624
>
> (gdb) c
>
>
> After I hit c, it will do the second lookup,
>
> Breakpoint 1, datapath_handle_read (dp=0x7ffff00008c0) at 
> /home/zhangwei1984/openNetVM-master/openNetVM/examples/flow_table/sdn.c:191
>
> 191                                 ret = onvm_ft_lookup(sdn_ft, fk, 
> (char**)&flow_entry);
>
> (gdb) print *sdn_ft
>
> $7 = {hash = 0x7fff32cce740, data = 0x7fff32cb0480 "", cnt = 1024, 
> entry_size = 56}
>
> (gdb) print *fk
>
> $8 = {src_addr = 419496202, dst_addr = 453050634, src_port = 53764, 
> dst_port = 11798, proto = 17 '\021'}
>
> (gdb) s
>
> onvm_ft_lookup (table=0x7fff32cbe4c0, key=0x7fff32b99c00, 
> data=0x7ffff68d2b00) at 
> /home/zhangwei1984/openNetVM-master/openNetVM/onvm/shared/onvm_flow_table.c:151
>
> 151 softrss = onvm_softrss(key);
>
> (gdb) n
>
> 152         printf("software rss %d\n", softrss);
>
> (gdb) n
>
> software rss 403183624
>
> 154         tbl_index = rte_hash_lookup_with_hash(table->hash, (const 
> void *)key, softrss);
>
> (gdb) print table->hash
>
> $9 = (struct rte_hash *) 0x7fff32cce740
>
> (gdb) print *key
>
> $10 = {src_addr = 419496202, dst_addr = 453050634, src_port = 53764, 
> dst_port = 11798, proto = 17 '\021'}
>
> (gdb) print softrss
>
> $11 = 403183624
>
> (gdb) n
>
>
> Program received signal SIGSEGV, Segmentation fault.
>
> 0x000000000045fb97 in __rte_hash_lookup_bulk ()
>
> (gdb) bt
>
> #0  0x000000000045fb97 in __rte_hash_lookup_bulk ()
>
> #1  0x0000000000000000 in ?? ()
>
>
> From the debug message, the parameters are exactly the same. I do not 
> know why it has the segmentation fault.
>
> my lookup function:
>
> int
>
> onvm_ft_lookup(struct onvm_ft* table, struct onvm_ft_ipv4_5tuple 
> *key, char** data) {
>
>         int32_t tbl_index;
>
>         uint32_t softrss;
>
>
>         softrss = onvm_softrss(key);
>
>         printf("software rss %d\n", softrss);
>
>
>         tbl_index = rte_hash_lookup_with_hash(table->hash, 
> (const void *)key, softrss);
>
>         if (tbl_index >= 0) {
>
>                 *data = onvm_ft_get_data(table, tbl_index);
>
>                 return 0;
>
>         }
>
>         else {
>
>                 return tbl_index;
>
>         }
>
> }
>
>
>
>
> At 2016-03-14 10:16:48, "Dhana Eadala" <edreddy@gmail.com <mailto:edreddy@gmail.com>> wrote:
> >We found a problem in dpdk-2.2 using under multi-process environment.
> >Here is the brief description how we are using the dpdk:
> >
> >We have two processes proc1, proc2 using dpdk. These proc1 and proc2 are
> >two different compiled binaries.
> >proc1 is started as primary process and proc2 as secondary process.
> >
> >proc1:
> >Calls srcHash = rte_hash_create("src_hash_name") to create rte_hash structure.
> >As part of this, this api initalized the rte_hash structure and set the
> >srcHash->rte_hash_cmp_eq to the address of memcmp() from proc1 address space.
> >
> >proc2:
> >calls srcHash =  rte_hash_find_existing("src_hash_name").
> >This function call returns the rte_hash created by proc1.
> >This srcHash->rte_hash_cmp_eq still points to the address of
> >memcmp() from proc1 address space.
> >Later proc2  calls
> >rte_hash_lookup_with_hash(srcHash, (const void*) &key, key.sig);
> >rte_hash_lookup_with_hash() invokes __rte_hash_lookup_with_hash(),
> >which in turn calls h->rte_hash_cmp_eq(key, k->key, h->key_len).
> >This leads to a crash as h->rte_hash_cmp_eq is an address
> >from proc1 address space and is invalid address in proc2 address space.
> >
> >We found, from dpdk documentation, that
> >
> >"
> > The use of function pointers between multiple processes
> > running based of different compiled
> > binaries is not supported, since the location of a given function
> > in one process may be different to
> > its location in a second. This prevents the librte_hash library
> > from behaving properly as in a  multi-
> > threaded instance, since it uses a pointer to the hash function internally.
> >
> > To work around this issue, it is recommended that
> > multi-process applications perform the hash
> > calculations by directly calling the hashing function
> > from the code and then using the
> > rte_hash_add_with_hash()/rte_hash_lookup_with_hash() functions
> > instead of the functions which do
> > the hashing internally, such as rte_hash_add()/rte_hash_lookup().
> >"
> >
> >We did follow the recommended steps by invoking rte_hash_lookup_with_hash().
> >It was no issue up to and including dpdk-2.0.
> >In later releases started crashing because rte_hash_cmp_eq is
> >introduced in dpdk-2.1
> >
> >We fixed it with the following patch and would like to
> >submit the patch to dpdk.org.
> >Patch is created such that, if anyone wanted to use dpdk in
> >multi-process environment with function pointers not shared, they need to
> >define RTE_LIB_MP_NO_FUNC_PTR in their Makefile.
> >Without defining this flag in Makefile, it works as it is now.
> >
> >Signed-off-by: Dhana Eadala <edreddy@gmail.com <mailto:edreddy@gmail.com>>
> >---
> > lib/librte_hash/rte_cuckoo_hash.c | 28 ++++++++++++++++++++++++++++
> > 1 file changed, 28 insertions(+)
> >
> >diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
> >index 3e3167c..0946777 100644
> >--- a/lib/librte_hash/rte_cuckoo_hash.c
> >+++ b/lib/librte_hash/rte_cuckoo_hash.c
> >@@ -594,7 +594,11 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
> > 				prim_bkt->signatures[i].alt == alt_hash) {
> > 			k = (struct rte_hash_key *) ((char *)keys +
> > 					prim_bkt->key_idx[i] * h->key_entry_size);
> >+#ifdef RTE_LIB_MP_NO_FUNC_PTR
> >+			if (memcmp(key, k->key, h->key_len) == 0) {
> >+#else
> > 			if (h->rte_hash_cmp_eq(key, k->key, h->key_len) == 0) {
> >+#endif
> > 				/* Enqueue index of free slot back in the ring. */
> > 				enqueue_slot_back(h, cached_free_slots, slot_id);
> > 				/* Update data */
> >@@ -614,7 +618,11 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
> > 				sec_bkt->signatures[i].current == alt_hash) {
> > 			k = (struct rte_hash_key *) ((char *)keys +
> > 					sec_bkt->key_idx[i] * h->key_entry_size);
> >+#ifdef RTE_LIB_MP_NO_FUNC_PTR
> >+			if (memcmp(key, k->key, h->key_len) == 0) {
> >+#else
> > 			if (h->rte_hash_cmp_eq(key, k->key, h->key_len) == 0) {
> >+#endif
> > 				/* Enqueue index of free slot back in the ring. */
> > 				enqueue_slot_back(h, cached_free_slots, slot_id);
> > 				/* Update data */
> >@@ -725,7 +733,11 @@ __rte_hash_lookup_with_hash(const struct rte_hash *h, const void *key,
> > 				bkt->signatures[i].sig != NULL_SIGNATURE) {
> > 			k = (struct rte_hash_key *) ((char *)keys +
> > 					bkt->key_idx[i] * h->key_entry_size);
> >+#ifdef RTE_LIB_MP_NO_FUNC_PTR
> >+			if (memcmp (key, k->key, h->key_len) == 0) {
> >+#else
> > 			if (h->rte_hash_cmp_eq(key, k->key, h->key_len) == 0) {
> >+#endif
> > 				if (data != NULL)
> > 					*data = k->pdata;
> > 				/*
> >@@ -748,7 +760,11 @@ __rte_hash_lookup_with_hash(const struct rte_hash *h, const void *key,
> > 				bkt->signatures[i].alt == sig) {
> > 			k = (struct rte_hash_key *) ((char *)keys +
> > 					bkt->key_idx[i] * h->key_entry_size);
> >+#ifdef RTE_LIB_MP_NO_FUNC_PTR
> >+			if (memcmp(key, k->key, h->key_len) == 0) {
> >+#else
> > 			if (h->rte_hash_cmp_eq(key, k->key, h->key_len) == 0) {
> >+#endif
> > 				if (data != NULL)
> > 					*data = k->pdata;
> > 				/*
> >@@ -840,7 +856,11 @@ __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
> > 				bkt->signatures[i].sig != NULL_SIGNATURE) {
> > 			k = (struct rte_hash_key *) ((char *)keys +
> > 					bkt->key_idx[i] * h->key_entry_size);
> >+#ifdef RTE_LIB_MP_NO_FUNC_PTR
> >+			if (memcmp(key, k->key, h->key_len) == 0) {
> >+#else
> > 			if (h->rte_hash_cmp_eq(key, k->key, h->key_len) == 0) {
> >+#endif
> > 				remove_entry(h, bkt, i);
> >
> > 				/*
> >@@ -863,7 +883,11 @@ __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
> > 				bkt->signatures[i].sig != NULL_SIGNATURE) {
> > 			k = (struct rte_hash_key *) ((char *)keys +
> > 					bkt->key_idx[i] * h->key_entry_size);
> >+#ifdef RTE_LIB_MP_NO_FUNC_PTR
> >+			if (memcmp(key, k->key, h->key_len) == 0) {
> >+#else
> > 			if (h->rte_hash_cmp_eq(key, k->key, h->key_len) == 0) {
> >+#endif
> > 				remove_entry(h, bkt, i);
> >
> > 				/*
> >@@ -980,7 +1004,11 @@ lookup_stage3(unsigned idx, const struct rte_hash_key *key_slot, const void * co
> > 	unsigned hit;
> > 	unsigned key_idx;
> >
> >+#ifdef RTE_LIB_MP_NO_FUNC_PTR
> >+	hit = !memcmp(key_slot->key, keys[idx], h->key_len);
> >+#else
> > 	hit = !h->rte_hash_cmp_eq(key_slot->key, keys[idx], h->key_len);
> >+#endif
> > 	if (data != NULL)
> > 		data[idx] = key_slot->pdata;
> >
> >--
> >2.5.0
> >
>
>
>
>