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authorTim O'Shea <tim.oshea753@gmail.com>2013-07-22 15:42:07 -0400
committerJohnathan Corgan <johnathan@corganlabs.com>2013-07-22 13:55:45 -0700
commit4c860926e164310bbb7d4c83bba3308419bd0677 (patch)
treef91d97bed3e90a6ff49f34a1b2599f52819b6e2f /gnuradio-runtime
parent28e4e6bce03aa4e5f69b9f37dbac7e4d2230961d (diff)
runtime: vmcircbuf_sysv_shm workaround for shmem race condition
Diffstat (limited to 'gnuradio-runtime')
-rw-r--r--gnuradio-runtime/lib/vmcircbuf_sysv_shm.cc180
1 files changed, 95 insertions, 85 deletions
diff --git a/gnuradio-runtime/lib/vmcircbuf_sysv_shm.cc b/gnuradio-runtime/lib/vmcircbuf_sysv_shm.cc
index f26edf44fc..4d8741807b 100644
--- a/gnuradio-runtime/lib/vmcircbuf_sysv_shm.cc
+++ b/gnuradio-runtime/lib/vmcircbuf_sysv_shm.cc
@@ -40,6 +40,7 @@
#include <stdio.h>
#include "pagesize.h"
+#define MAX_SYSV_SHM_ATTEMPTS 3
namespace gr {
@@ -60,93 +61,102 @@ namespace gr {
throw std::runtime_error("gr::vmcircbuf_sysv_shm");
}
- int shmid_guard = -1;
- int shmid1 = -1;
- int shmid2 = -1;
-
- // We use this as a guard page. We'll map it read-only on both ends of the buffer.
- // Ideally we'd map it no access, but I don't think that's possible with SysV
- if((shmid_guard = shmget(IPC_PRIVATE, pagesize, IPC_CREAT | 0400)) == -1) {
- perror("gr::vmcircbuf_sysv_shm: shmget (0)");
- throw std::runtime_error("gr::vmcircbuf_sysv_shm");
- }
-
- if((shmid2 = shmget(IPC_PRIVATE, 2 * size + 2 * pagesize, IPC_CREAT | 0700)) == -1) {
- perror("gr::vmcircbuf_sysv_shm: shmget(1)");
- shmctl(shmid_guard, IPC_RMID, 0);
- throw std::runtime_error ("gr::vmcircbuf_sysv_shm");
- }
-
- if((shmid1 = shmget(IPC_PRIVATE, size, IPC_CREAT | 0700)) == -1) {
- perror("gr::vmcircbuf_sysv_shm: shmget (2)");
- shmctl(shmid_guard, IPC_RMID, 0);
- shmctl(shmid2, IPC_RMID, 0);
- throw std::runtime_error("gr::vmcircbuf_sysv_shm");
- }
-
- void *first_copy = shmat (shmid2, 0, 0);
- if(first_copy == (void *) -1) {
- perror("gr::vmcircbuf_sysv_shm: shmat(1)");
- shmctl(shmid_guard, IPC_RMID, 0);
- shmctl(shmid2, IPC_RMID, 0);
- shmctl(shmid1, IPC_RMID, 0);
- throw std::runtime_error("gr::vmcircbuf_sysv_shm");
- }
-
- shmctl(shmid2, IPC_RMID, 0);
-
- // There may be a race between our detach and attach.
- //
- // If the system allocates all shared memory segments at the same
- // virtual addresses in all processes and if the system allocates
- // some other segment to first_copy or first_copoy + size between
- // our detach and attach, the attaches below could fail [I've never
- // seen it fail for this reason].
- shmdt(first_copy);
-
- // first read-only guard page
- if(shmat(shmid_guard, first_copy, SHM_RDONLY) == (void *) -1) {
- perror("gr::vmcircbuf_sysv_shm: shmat(2)");
- shmctl(shmid_guard, IPC_RMID, 0);
- shmctl(shmid1, IPC_RMID, 0);
- throw std::runtime_error("gr::vmcircbuf_sysv_shm");
+ // Attempt to allocate buffers (handle bad_alloc errors)
+ int attempts_remain(MAX_SYSV_SHM_ATTEMPTS);
+ while(attempts_remain-- > 0){
+
+ int shmid_guard = -1;
+ int shmid1 = -1;
+ int shmid2 = -1;
+
+ // We use this as a guard page. We'll map it read-only on both ends of the buffer.
+ // Ideally we'd map it no access, but I don't think that's possible with SysV
+ if((shmid_guard = shmget(IPC_PRIVATE, pagesize, IPC_CREAT | 0400)) == -1) {
+ perror("gr::vmcircbuf_sysv_shm: shmget (0)");
+ continue;
+ }
+
+ if((shmid2 = shmget(IPC_PRIVATE, 2 * size + 2 * pagesize, IPC_CREAT | 0700)) == -1) {
+ perror("gr::vmcircbuf_sysv_shm: shmget(1)");
+ shmctl(shmid_guard, IPC_RMID, 0);
+ continue;
+ }
+
+ if((shmid1 = shmget(IPC_PRIVATE, size, IPC_CREAT | 0700)) == -1) {
+ perror("gr::vmcircbuf_sysv_shm: shmget (2)");
+ shmctl(shmid_guard, IPC_RMID, 0);
+ shmctl(shmid2, IPC_RMID, 0);
+ continue;
+ }
+
+ void *first_copy = shmat (shmid2, 0, 0);
+ if(first_copy == (void *) -1) {
+ perror("gr::vmcircbuf_sysv_shm: shmat(1)");
+ shmctl(shmid_guard, IPC_RMID, 0);
+ shmctl(shmid2, IPC_RMID, 0);
+ shmctl(shmid1, IPC_RMID, 0);
+ continue;
+ }
+
+ shmctl(shmid2, IPC_RMID, 0);
+
+ // There may be a race between our detach and attach.
+ //
+ // If the system allocates all shared memory segments at the same
+ // virtual addresses in all processes and if the system allocates
+ // some other segment to first_copy or first_copoy + size between
+ // our detach and attach, the attaches below could fail [I've never
+ // seen it fail for this reason].
+ shmdt(first_copy);
+
+ // first read-only guard page
+ if(shmat(shmid_guard, first_copy, SHM_RDONLY) == (void *) -1) {
+ perror("gr::vmcircbuf_sysv_shm: shmat(2)");
+ shmctl(shmid_guard, IPC_RMID, 0);
+ shmctl(shmid1, IPC_RMID, 0);
+ continue;
+ }
+
+ // first copy
+ if(shmat (shmid1, (char*)first_copy + pagesize, 0) == (void *) -1) {
+ perror("gr::vmcircbuf_sysv_shm: shmat (3)");
+ shmctl(shmid_guard, IPC_RMID, 0);
+ shmctl(shmid1, IPC_RMID, 0);
+ shmdt(first_copy);
+ continue;
+ }
+
+ // second copy
+ if(shmat (shmid1, (char*)first_copy + pagesize + size, 0) == (void *) -1) {
+ perror("gr::vmcircbuf_sysv_shm: shmat (4)");
+ shmctl(shmid_guard, IPC_RMID, 0);
+ shmctl(shmid1, IPC_RMID, 0);
+ shmdt((char *)first_copy + pagesize);
+ continue;
+ }
+
+ // second read-only guard page
+ if(shmat(shmid_guard, (char*)first_copy + pagesize + 2 * size, SHM_RDONLY) == (void *) -1) {
+ perror("gr::vmcircbuf_sysv_shm: shmat(5)");
+ shmctl(shmid_guard, IPC_RMID, 0);
+ shmctl(shmid1, IPC_RMID, 0);
+ shmdt(first_copy);
+ shmdt((char *)first_copy + pagesize);
+ shmdt((char *)first_copy + pagesize + size);
+ continue;
+ }
+
+ shmctl(shmid1, IPC_RMID, 0);
+ shmctl(shmid_guard, IPC_RMID, 0);
+
+ // Now remember the important stuff
+ d_base = (char*)first_copy + pagesize;
+ d_size = size;
+ break;
}
-
- // first copy
- if(shmat (shmid1, (char*)first_copy + pagesize, 0) == (void *) -1) {
- perror("gr::vmcircbuf_sysv_shm: shmat (3)");
- shmctl(shmid_guard, IPC_RMID, 0);
- shmctl(shmid1, IPC_RMID, 0);
- shmdt(first_copy);
- throw std::runtime_error("gr::vmcircbuf_sysv_shm");
+ if(attempts_remain<0){
+ throw std::runtime_error("gr_vmcircbuf_sysv_shm");
}
-
- // second copy
- if(shmat (shmid1, (char*)first_copy + pagesize + size, 0) == (void *) -1) {
- perror("gr::vmcircbuf_sysv_shm: shmat (4)");
- shmctl(shmid_guard, IPC_RMID, 0);
- shmctl(shmid1, IPC_RMID, 0);
- shmdt((char *)first_copy + pagesize);
- throw std::runtime_error("gr::vmcircbuf_sysv_shm");
- }
-
- // second read-only guard page
- if(shmat(shmid_guard, (char*)first_copy + pagesize + 2 * size, SHM_RDONLY) == (void *) -1) {
- perror("gr::vmcircbuf_sysv_shm: shmat(5)");
- shmctl(shmid_guard, IPC_RMID, 0);
- shmctl(shmid1, IPC_RMID, 0);
- shmdt(first_copy);
- shmdt((char *)first_copy + pagesize);
- shmdt((char *)first_copy + pagesize + size);
- throw std::runtime_error ("gr::vmcircbuf_sysv_shm");
- }
-
- shmctl(shmid1, IPC_RMID, 0);
- shmctl(shmid_guard, IPC_RMID, 0);
-
- // Now remember the important stuff
- d_base = (char*)first_copy + pagesize;
- d_size = size;
#endif
}
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