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Commit 10f129ca authored by Christopher Tate's avatar Christopher Tate
Browse files

Fix hang after end of backup 

The buggy behavior was that the 'adb backup ....' host command line
invocation would hang forever, even after the backup finished and
the forked device-side subprocess had been reaped.  The reason for
this is that the device adbd end of the socketpair used to send
the data back from the forked subprocess was still stuck readable
even after the remote end of it had been closed.

With this patch, the thread whose job it is to waitpid() in order
to harvest the forked child process also closes the local (adbd)
end of the socketpair.  This makes the fdevent logic notice that
the socket is dead, at which point it cleans up everything including
the communication back to the host.

Change-Id: I90e7e4e5db36c5a6f7363708b29a6d2c56d1250e
parent 5b811fa5

adb/backup_service.c

+17 −4
Original line number Diff line number Diff line
@@ -22,6 +22,11 @@ 
#define TRACE_TAG  TRACE_ADB

#include "adb.h"



typedef struct {

    pid_t pid;

    int fd;

} backup_harvest_params;



// socketpair but do *not* mark as close_on_exec

static int backup_socketpair(int sv[2]) {

    int rc = unix_socketpair( AF_UNIX, SOCK_STREAM, 0, sv );
@@ -31,11 +36,14 @@ static int backup_socketpair(int sv[2]) { 
    return 0;

}



static void* backup_child_waiter(void* pid_cookie) {

// harvest the child process then close the read end of the socketpair

static void* backup_child_waiter(void* args) {

    int status;

    backup_harvest_params* params = (backup_harvest_params*) args;



    waitpid((pid_t) pid_cookie, &status, 0);

    D("harvested backup/restore child, status=%d\n", status);

    waitpid(params->pid, &status, 0);

    adb_close(params->fd);

    free(params);

    return NULL;

}
@@ -124,14 +132,19 @@ int backup_service(BackupOperation op, char* args) { 
        exit(-1);

    } else {

        adb_thread_t t;

        backup_harvest_params* params;



        // parent, i.e. adbd -- close the sending half of the socket

        D("fork() returned pid %d\n", pid);

        adb_close(s[1]);



        // spin a thread to harvest the child process

        if (adb_thread_create(&t, backup_child_waiter, (void*)pid)) {

        params = (backup_harvest_params*) malloc(sizeof(backup_harvest_params));

        params->pid = pid;

        params->fd = s[0];

        if (adb_thread_create(&t, backup_child_waiter, params)) {

            adb_close(s[0]);

            free(params);

            D("Unable to create child harvester\n");

            return -1;

        }