Josh31,
Tosfos to the daf (DH v’Al) says that when one is concerned that he will be forced to sin (such as by being tortured until he sins), he is permitted to kill himself. The Gemara in Gittin (57b) relates the tragic story of four hundred Jewish children who were captured and were being taken to be used for immoral purposes, who chose to drown themselves in the sea rather than to be forced to sin. According to the opinion of R’ Nachman Bar Yitzchak in Gittin 57b, it refers to Chachamim who give their lives for learning, which may clearly be the case with R’ Chanina.
Basically, where there is a question of yehareg v’ al yaavor, chosing death over violating the three cardinal sins of Judaism , as was the case with the children in Gittin 57b and R’ Chanina, the requirement does extend to active suicide, according to Rabbeinu Tam in the same Tosfos, citing the same story of the children in Gittin. The Chiddushei HaRitva here also allows such acts of suicide. Even in instances where one would be forced to violate even the smallest detail of observance, during times of persecution, martyrdom must be accepted; in a time of general persecution of Jews one should prefer martyrdom when required to transgress a law even in private(Sanhedrin 74b-75a, Yesodei HaTorah 5:1-4, and the Shulchan Aruch Yoreh Deah 157:1). The Rosh says that one one is allowed to accept martyrdom even in cases where the halacha doesn’t require it (Avodah Zarah 2:9). One who transgresses the halacha instead of submitting to martyrdom where martyrdom is enjoined, can not be punished in the courts, since the transgression is committed under duress, but he must be regarded as a defiler of G-d’s name; and if he persists in living in the same place and in continuing the transgression when he can escape, he forfeits his portion in the future world and will be assigned to the lowest chambers of hell, according to the Rambam.
There is a clear makor for active suicide; i.e. taking one’s life when there is the possibility one will be faced with transgressing the Torah.