lwIP: calling pbuf_free in interrupt context without protection in RAW API mode

[Yujian Zhang]

In bare-metal application derived from a hello world template when default configuration is used, emacps_send_handler will be called in interrupt context, in which xemacps_process_sent_bds calls pbuf_free.

embeddedsw/ThirdParty/sw_services/lwip213/src/contrib/ports/xilinx/netif/xemacpsif_dma.c

Lines 289 to 305 in 8fca1ac

 void emacps_send_handler(void *arg) 
 { 
 	struct xemac_s *xemac; 
 	xemacpsif_s   *xemacpsif; 
 	XEmacPs_BdRing *txringptr; 
 	u32_t regval; 
 #if !NO_SYS 
 	xInsideISR++; 
 #endif 
 	xemac = (struct xemac_s *)(arg); 
 	xemacpsif = (xemacpsif_s *)(xemac->state); 
 	txringptr = &(XEmacPs_GetTxRing(&xemacpsif->emacps)); 
 	regval = XEmacPs_ReadReg(xemacpsif->emacps.Config.BaseAddress, XEMACPS_TXSR_OFFSET); 
 	XEmacPs_WriteReg(xemacpsif->emacps.Config.BaseAddress,XEMACPS_TXSR_OFFSET, regval); 
  
 	/* If Transmit done interrupt is asserted, process completed BD's */ 
 	xemacps_process_sent_bds(xemacpsif, txringptr); 

However, the protection macro for calling mem_free/pbuf_free, LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT, will only be emit to lwipopts.h in SOCKET API mode:

embeddedsw/ThirdParty/sw_services/lwip213/data/lwip213.tcl

Lines 546 to 575 in 8fca1ac

 if {$api_mode == "SOCKET_API"} { 
 	set sw_proc_handle [hsi::get_sw_processor] 
 	set os_handle [hsi::get_os] 
 	set os_name [common::get_property NAME $os_handle] 
 	if { [string compare -nocase "freertos10_xilinx" $os_name] == 0} { 
 		# mbox options 
 		set lwip_tcpip_core_locking_input	[common::get_property CONFIG.lwip_tcpip_core_locking_input $libhandle] 
 		set tcpip_mbox_size	[common::get_property CONFIG.tcpip_mbox_size $libhandle] 
 		set default_tcp_recvmbox_size	[common::get_property CONFIG.default_tcp_recvmbox_size $libhandle] 
 		set default_udp_recvmbox_size	[common::get_property CONFIG.default_udp_recvmbox_size $libhandle] 
 		puts $lwipopts_fd "\#define DEFAULT_THREAD_PRIO $thread_prio" 
 		if {$processor_type == "psu_cortexa53" || $processor_type == "psv_cortexa72" } { 
 			puts $lwipopts_fd "\#define TCPIP_THREAD_PRIO ($thread_prio)" 
 		} else { 
 		puts $lwipopts_fd "\#define TCPIP_THREAD_PRIO ($thread_prio + 1)" 
 		} 
 		puts $lwipopts_fd "\#define TCPIP_THREAD_STACKSIZE 1024" 
 		puts $lwipopts_fd "\#define DEFAULT_TCP_RECVMBOX_SIZE 	$default_tcp_recvmbox_size" 
 		puts $lwipopts_fd "\#define DEFAULT_ACCEPTMBOX_SIZE 	5" 
 		puts $lwipopts_fd "\#define TCPIP_MBOX_SIZE		$tcpip_mbox_size" 
 		puts $lwipopts_fd "\#define DEFAULT_UDP_RECVMBOX_SIZE 	$default_udp_recvmbox_size" 
 		puts $lwipopts_fd "\#define DEFAULT_RAW_RECVMBOX_SIZE	30" 
 		puts $lwipopts_fd "\#define LWIP_COMPAT_MUTEX 0" 
 		puts $lwipopts_fd "\#define LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT 1" 
 		if {$lwip_tcpip_core_locking_input == true} { 
 			puts $lwipopts_fd "\#define LWIP_TCPIP_CORE_LOCKING_INPUT 1" 
 		} 
 		puts $lwipopts_fd "" 
 	} 
 } 

The user manual from lwIP can be found below:

embeddedsw/ThirdParty/sw_services/lwip213/src/lwip-2.1.3/CHANGELOG

Lines 2391 to 2395 in 8fca1ac

 2008-06-30 Simon Goldschmidt 
 * mem.c, opt.h, stats.h: fixed bug #21433: Calling mem_free/pbuf_free from 
   interrupt context isn't safe: LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT allows 
   mem_free to run between mem_malloc iterations. Added illegal counter for 
   mem stats.